11da177e4SLinus Torvalds /* 21da177e4SLinus Torvalds * linux/fs/buffer.c 31da177e4SLinus Torvalds * 41da177e4SLinus Torvalds * Copyright (C) 1991, 1992, 2002 Linus Torvalds 51da177e4SLinus Torvalds */ 61da177e4SLinus Torvalds 71da177e4SLinus Torvalds /* 81da177e4SLinus Torvalds * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95 91da177e4SLinus Torvalds * 101da177e4SLinus Torvalds * Removed a lot of unnecessary code and simplified things now that 111da177e4SLinus Torvalds * the buffer cache isn't our primary cache - Andrew Tridgell 12/96 121da177e4SLinus Torvalds * 131da177e4SLinus Torvalds * Speed up hash, lru, and free list operations. Use gfp() for allocating 141da177e4SLinus Torvalds * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM 151da177e4SLinus Torvalds * 161da177e4SLinus Torvalds * Added 32k buffer block sizes - these are required older ARM systems. - RMK 171da177e4SLinus Torvalds * 181da177e4SLinus Torvalds * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de> 191da177e4SLinus Torvalds */ 201da177e4SLinus Torvalds 211da177e4SLinus Torvalds #include <linux/kernel.h> 221da177e4SLinus Torvalds #include <linux/syscalls.h> 231da177e4SLinus Torvalds #include <linux/fs.h> 241da177e4SLinus Torvalds #include <linux/mm.h> 251da177e4SLinus Torvalds #include <linux/percpu.h> 261da177e4SLinus Torvalds #include <linux/slab.h> 2716f7e0feSRandy Dunlap #include <linux/capability.h> 281da177e4SLinus Torvalds #include <linux/blkdev.h> 291da177e4SLinus Torvalds #include <linux/file.h> 301da177e4SLinus Torvalds #include <linux/quotaops.h> 311da177e4SLinus Torvalds #include <linux/highmem.h> 321da177e4SLinus Torvalds #include <linux/module.h> 331da177e4SLinus Torvalds #include <linux/writeback.h> 341da177e4SLinus Torvalds #include <linux/hash.h> 351da177e4SLinus Torvalds #include <linux/suspend.h> 361da177e4SLinus Torvalds #include <linux/buffer_head.h> 3755e829afSAndrew Morton #include <linux/task_io_accounting_ops.h> 381da177e4SLinus Torvalds #include <linux/bio.h> 391da177e4SLinus Torvalds #include <linux/notifier.h> 401da177e4SLinus Torvalds #include <linux/cpu.h> 411da177e4SLinus Torvalds #include <linux/bitops.h> 421da177e4SLinus Torvalds #include <linux/mpage.h> 43fb1c8f93SIngo Molnar #include <linux/bit_spinlock.h> 441da177e4SLinus Torvalds 451da177e4SLinus Torvalds static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); 461da177e4SLinus Torvalds 471da177e4SLinus Torvalds #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers) 481da177e4SLinus Torvalds 491da177e4SLinus Torvalds inline void 501da177e4SLinus Torvalds init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private) 511da177e4SLinus Torvalds { 521da177e4SLinus Torvalds bh->b_end_io = handler; 531da177e4SLinus Torvalds bh->b_private = private; 541da177e4SLinus Torvalds } 551fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(init_buffer); 561da177e4SLinus Torvalds 571da177e4SLinus Torvalds static int sync_buffer(void *word) 581da177e4SLinus Torvalds { 591da177e4SLinus Torvalds struct block_device *bd; 601da177e4SLinus Torvalds struct buffer_head *bh 611da177e4SLinus Torvalds = container_of(word, struct buffer_head, b_state); 621da177e4SLinus Torvalds 631da177e4SLinus Torvalds smp_mb(); 641da177e4SLinus Torvalds bd = bh->b_bdev; 651da177e4SLinus Torvalds if (bd) 661da177e4SLinus Torvalds blk_run_address_space(bd->bd_inode->i_mapping); 671da177e4SLinus Torvalds io_schedule(); 681da177e4SLinus Torvalds return 0; 691da177e4SLinus Torvalds } 701da177e4SLinus Torvalds 71fc9b52cdSHarvey Harrison void __lock_buffer(struct buffer_head *bh) 721da177e4SLinus Torvalds { 731da177e4SLinus Torvalds wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer, 741da177e4SLinus Torvalds TASK_UNINTERRUPTIBLE); 751da177e4SLinus Torvalds } 761da177e4SLinus Torvalds EXPORT_SYMBOL(__lock_buffer); 771da177e4SLinus Torvalds 78fc9b52cdSHarvey Harrison void unlock_buffer(struct buffer_head *bh) 791da177e4SLinus Torvalds { 8051b07fc3SNick Piggin clear_bit_unlock(BH_Lock, &bh->b_state); 811da177e4SLinus Torvalds smp_mb__after_clear_bit(); 821da177e4SLinus Torvalds wake_up_bit(&bh->b_state, BH_Lock); 831da177e4SLinus Torvalds } 841fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(unlock_buffer); 851da177e4SLinus Torvalds 861da177e4SLinus Torvalds /* 871da177e4SLinus Torvalds * Block until a buffer comes unlocked. This doesn't stop it 881da177e4SLinus Torvalds * from becoming locked again - you have to lock it yourself 891da177e4SLinus Torvalds * if you want to preserve its state. 901da177e4SLinus Torvalds */ 911da177e4SLinus Torvalds void __wait_on_buffer(struct buffer_head * bh) 921da177e4SLinus Torvalds { 931da177e4SLinus Torvalds wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE); 941da177e4SLinus Torvalds } 951fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(__wait_on_buffer); 961da177e4SLinus Torvalds 971da177e4SLinus Torvalds static void 981da177e4SLinus Torvalds __clear_page_buffers(struct page *page) 991da177e4SLinus Torvalds { 1001da177e4SLinus Torvalds ClearPagePrivate(page); 1014c21e2f2SHugh Dickins set_page_private(page, 0); 1021da177e4SLinus Torvalds page_cache_release(page); 1031da177e4SLinus Torvalds } 1041da177e4SLinus Torvalds 10508bafc03SKeith Mannthey 10608bafc03SKeith Mannthey static int quiet_error(struct buffer_head *bh) 10708bafc03SKeith Mannthey { 10808bafc03SKeith Mannthey if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit()) 10908bafc03SKeith Mannthey return 0; 11008bafc03SKeith Mannthey return 1; 11108bafc03SKeith Mannthey } 11208bafc03SKeith Mannthey 11308bafc03SKeith Mannthey 1141da177e4SLinus Torvalds static void buffer_io_error(struct buffer_head *bh) 1151da177e4SLinus Torvalds { 1161da177e4SLinus Torvalds char b[BDEVNAME_SIZE]; 1171da177e4SLinus Torvalds printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", 1181da177e4SLinus Torvalds bdevname(bh->b_bdev, b), 1191da177e4SLinus Torvalds (unsigned long long)bh->b_blocknr); 1201da177e4SLinus Torvalds } 1211da177e4SLinus Torvalds 1221da177e4SLinus Torvalds /* 12368671f35SDmitry Monakhov * End-of-IO handler helper function which does not touch the bh after 12468671f35SDmitry Monakhov * unlocking it. 12568671f35SDmitry Monakhov * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but 12668671f35SDmitry Monakhov * a race there is benign: unlock_buffer() only use the bh's address for 12768671f35SDmitry Monakhov * hashing after unlocking the buffer, so it doesn't actually touch the bh 12868671f35SDmitry Monakhov * itself. 1291da177e4SLinus Torvalds */ 13068671f35SDmitry Monakhov static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) 1311da177e4SLinus Torvalds { 1321da177e4SLinus Torvalds if (uptodate) { 1331da177e4SLinus Torvalds set_buffer_uptodate(bh); 1341da177e4SLinus Torvalds } else { 1351da177e4SLinus Torvalds /* This happens, due to failed READA attempts. */ 1361da177e4SLinus Torvalds clear_buffer_uptodate(bh); 1371da177e4SLinus Torvalds } 1381da177e4SLinus Torvalds unlock_buffer(bh); 13968671f35SDmitry Monakhov } 14068671f35SDmitry Monakhov 14168671f35SDmitry Monakhov /* 14268671f35SDmitry Monakhov * Default synchronous end-of-IO handler.. Just mark it up-to-date and 14368671f35SDmitry Monakhov * unlock the buffer. This is what ll_rw_block uses too. 14468671f35SDmitry Monakhov */ 14568671f35SDmitry Monakhov void end_buffer_read_sync(struct buffer_head *bh, int uptodate) 14668671f35SDmitry Monakhov { 14768671f35SDmitry Monakhov __end_buffer_read_notouch(bh, uptodate); 1481da177e4SLinus Torvalds put_bh(bh); 1491da177e4SLinus Torvalds } 1501fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(end_buffer_read_sync); 1511da177e4SLinus Torvalds 1521da177e4SLinus Torvalds void end_buffer_write_sync(struct buffer_head *bh, int uptodate) 1531da177e4SLinus Torvalds { 1541da177e4SLinus Torvalds char b[BDEVNAME_SIZE]; 1551da177e4SLinus Torvalds 1561da177e4SLinus Torvalds if (uptodate) { 1571da177e4SLinus Torvalds set_buffer_uptodate(bh); 1581da177e4SLinus Torvalds } else { 15908bafc03SKeith Mannthey if (!buffer_eopnotsupp(bh) && !quiet_error(bh)) { 1601da177e4SLinus Torvalds buffer_io_error(bh); 1611da177e4SLinus Torvalds printk(KERN_WARNING "lost page write due to " 1621da177e4SLinus Torvalds "I/O error on %s\n", 1631da177e4SLinus Torvalds bdevname(bh->b_bdev, b)); 1641da177e4SLinus Torvalds } 1651da177e4SLinus Torvalds set_buffer_write_io_error(bh); 1661da177e4SLinus Torvalds clear_buffer_uptodate(bh); 1671da177e4SLinus Torvalds } 1681da177e4SLinus Torvalds unlock_buffer(bh); 1691da177e4SLinus Torvalds put_bh(bh); 1701da177e4SLinus Torvalds } 1711fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(end_buffer_write_sync); 1721da177e4SLinus Torvalds 1731da177e4SLinus Torvalds /* 1741da177e4SLinus Torvalds * Various filesystems appear to want __find_get_block to be non-blocking. 1751da177e4SLinus Torvalds * But it's the page lock which protects the buffers. To get around this, 1761da177e4SLinus Torvalds * we get exclusion from try_to_free_buffers with the blockdev mapping's 1771da177e4SLinus Torvalds * private_lock. 1781da177e4SLinus Torvalds * 1791da177e4SLinus Torvalds * Hack idea: for the blockdev mapping, i_bufferlist_lock contention 1801da177e4SLinus Torvalds * may be quite high. This code could TryLock the page, and if that 1811da177e4SLinus Torvalds * succeeds, there is no need to take private_lock. (But if 1821da177e4SLinus Torvalds * private_lock is contended then so is mapping->tree_lock). 1831da177e4SLinus Torvalds */ 1841da177e4SLinus Torvalds static struct buffer_head * 185385fd4c5SCoywolf Qi Hunt __find_get_block_slow(struct block_device *bdev, sector_t block) 1861da177e4SLinus Torvalds { 1871da177e4SLinus Torvalds struct inode *bd_inode = bdev->bd_inode; 1881da177e4SLinus Torvalds struct address_space *bd_mapping = bd_inode->i_mapping; 1891da177e4SLinus Torvalds struct buffer_head *ret = NULL; 1901da177e4SLinus Torvalds pgoff_t index; 1911da177e4SLinus Torvalds struct buffer_head *bh; 1921da177e4SLinus Torvalds struct buffer_head *head; 1931da177e4SLinus Torvalds struct page *page; 1941da177e4SLinus Torvalds int all_mapped = 1; 1951da177e4SLinus Torvalds 1961da177e4SLinus Torvalds index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); 1971da177e4SLinus Torvalds page = find_get_page(bd_mapping, index); 1981da177e4SLinus Torvalds if (!page) 1991da177e4SLinus Torvalds goto out; 2001da177e4SLinus Torvalds 2011da177e4SLinus Torvalds spin_lock(&bd_mapping->private_lock); 2021da177e4SLinus Torvalds if (!page_has_buffers(page)) 2031da177e4SLinus Torvalds goto out_unlock; 2041da177e4SLinus Torvalds head = page_buffers(page); 2051da177e4SLinus Torvalds bh = head; 2061da177e4SLinus Torvalds do { 20797f76d3dSNikanth Karthikesan if (!buffer_mapped(bh)) 20897f76d3dSNikanth Karthikesan all_mapped = 0; 20997f76d3dSNikanth Karthikesan else if (bh->b_blocknr == block) { 2101da177e4SLinus Torvalds ret = bh; 2111da177e4SLinus Torvalds get_bh(bh); 2121da177e4SLinus Torvalds goto out_unlock; 2131da177e4SLinus Torvalds } 2141da177e4SLinus Torvalds bh = bh->b_this_page; 2151da177e4SLinus Torvalds } while (bh != head); 2161da177e4SLinus Torvalds 2171da177e4SLinus Torvalds /* we might be here because some of the buffers on this page are 2181da177e4SLinus Torvalds * not mapped. This is due to various races between 2191da177e4SLinus Torvalds * file io on the block device and getblk. It gets dealt with 2201da177e4SLinus Torvalds * elsewhere, don't buffer_error if we had some unmapped buffers 2211da177e4SLinus Torvalds */ 2221da177e4SLinus Torvalds if (all_mapped) { 2231da177e4SLinus Torvalds printk("__find_get_block_slow() failed. " 2241da177e4SLinus Torvalds "block=%llu, b_blocknr=%llu\n", 225205f87f6SBadari Pulavarty (unsigned long long)block, 226205f87f6SBadari Pulavarty (unsigned long long)bh->b_blocknr); 227205f87f6SBadari Pulavarty printk("b_state=0x%08lx, b_size=%zu\n", 228205f87f6SBadari Pulavarty bh->b_state, bh->b_size); 2291da177e4SLinus Torvalds printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); 2301da177e4SLinus Torvalds } 2311da177e4SLinus Torvalds out_unlock: 2321da177e4SLinus Torvalds spin_unlock(&bd_mapping->private_lock); 2331da177e4SLinus Torvalds page_cache_release(page); 2341da177e4SLinus Torvalds out: 2351da177e4SLinus Torvalds return ret; 2361da177e4SLinus Torvalds } 2371da177e4SLinus Torvalds 2381da177e4SLinus Torvalds /* If invalidate_buffers() will trash dirty buffers, it means some kind 2391da177e4SLinus Torvalds of fs corruption is going on. Trashing dirty data always imply losing 2401da177e4SLinus Torvalds information that was supposed to be just stored on the physical layer 2411da177e4SLinus Torvalds by the user. 2421da177e4SLinus Torvalds 2431da177e4SLinus Torvalds Thus invalidate_buffers in general usage is not allwowed to trash 2441da177e4SLinus Torvalds dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to 2451da177e4SLinus Torvalds be preserved. These buffers are simply skipped. 2461da177e4SLinus Torvalds 2471da177e4SLinus Torvalds We also skip buffers which are still in use. For example this can 2481da177e4SLinus Torvalds happen if a userspace program is reading the block device. 2491da177e4SLinus Torvalds 2501da177e4SLinus Torvalds NOTE: In the case where the user removed a removable-media-disk even if 2511da177e4SLinus Torvalds there's still dirty data not synced on disk (due a bug in the device driver 2521da177e4SLinus Torvalds or due an error of the user), by not destroying the dirty buffers we could 2531da177e4SLinus Torvalds generate corruption also on the next media inserted, thus a parameter is 2541da177e4SLinus Torvalds necessary to handle this case in the most safe way possible (trying 2551da177e4SLinus Torvalds to not corrupt also the new disk inserted with the data belonging to 2561da177e4SLinus Torvalds the old now corrupted disk). Also for the ramdisk the natural thing 2571da177e4SLinus Torvalds to do in order to release the ramdisk memory is to destroy dirty buffers. 2581da177e4SLinus Torvalds 2591da177e4SLinus Torvalds These are two special cases. Normal usage imply the device driver 2601da177e4SLinus Torvalds to issue a sync on the device (without waiting I/O completion) and 2611da177e4SLinus Torvalds then an invalidate_buffers call that doesn't trash dirty buffers. 2621da177e4SLinus Torvalds 2631da177e4SLinus Torvalds For handling cache coherency with the blkdev pagecache the 'update' case 2641da177e4SLinus Torvalds is been introduced. It is needed to re-read from disk any pinned 2651da177e4SLinus Torvalds buffer. NOTE: re-reading from disk is destructive so we can do it only 2661da177e4SLinus Torvalds when we assume nobody is changing the buffercache under our I/O and when 2671da177e4SLinus Torvalds we think the disk contains more recent information than the buffercache. 2681da177e4SLinus Torvalds The update == 1 pass marks the buffers we need to update, the update == 2 2691da177e4SLinus Torvalds pass does the actual I/O. */ 270f98393a6SPeter Zijlstra void invalidate_bdev(struct block_device *bdev) 2711da177e4SLinus Torvalds { 2720e1dfc66SAndrew Morton struct address_space *mapping = bdev->bd_inode->i_mapping; 2730e1dfc66SAndrew Morton 2740e1dfc66SAndrew Morton if (mapping->nrpages == 0) 2750e1dfc66SAndrew Morton return; 2760e1dfc66SAndrew Morton 2771da177e4SLinus Torvalds invalidate_bh_lrus(); 278fa4b9074STejun Heo lru_add_drain_all(); /* make sure all lru add caches are flushed */ 279fc0ecff6SAndrew Morton invalidate_mapping_pages(mapping, 0, -1); 2801da177e4SLinus Torvalds } 2811fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(invalidate_bdev); 2821da177e4SLinus Torvalds 2831da177e4SLinus Torvalds /* 2845b0830cbSJens Axboe * Kick the writeback threads then try to free up some ZONE_NORMAL memory. 2851da177e4SLinus Torvalds */ 2861da177e4SLinus Torvalds static void free_more_memory(void) 2871da177e4SLinus Torvalds { 28819770b32SMel Gorman struct zone *zone; 2890e88460dSMel Gorman int nid; 2901da177e4SLinus Torvalds 29103ba3782SJens Axboe wakeup_flusher_threads(1024); 2921da177e4SLinus Torvalds yield(); 2931da177e4SLinus Torvalds 2940e88460dSMel Gorman for_each_online_node(nid) { 29519770b32SMel Gorman (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), 29619770b32SMel Gorman gfp_zone(GFP_NOFS), NULL, 29719770b32SMel Gorman &zone); 29819770b32SMel Gorman if (zone) 29954a6eb5cSMel Gorman try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, 300327c0e96SKAMEZAWA Hiroyuki GFP_NOFS, NULL); 3011da177e4SLinus Torvalds } 3021da177e4SLinus Torvalds } 3031da177e4SLinus Torvalds 3041da177e4SLinus Torvalds /* 3051da177e4SLinus Torvalds * I/O completion handler for block_read_full_page() - pages 3061da177e4SLinus Torvalds * which come unlocked at the end of I/O. 3071da177e4SLinus Torvalds */ 3081da177e4SLinus Torvalds static void end_buffer_async_read(struct buffer_head *bh, int uptodate) 3091da177e4SLinus Torvalds { 3101da177e4SLinus Torvalds unsigned long flags; 311a3972203SNick Piggin struct buffer_head *first; 3121da177e4SLinus Torvalds struct buffer_head *tmp; 3131da177e4SLinus Torvalds struct page *page; 3141da177e4SLinus Torvalds int page_uptodate = 1; 3151da177e4SLinus Torvalds 3161da177e4SLinus Torvalds BUG_ON(!buffer_async_read(bh)); 3171da177e4SLinus Torvalds 3181da177e4SLinus Torvalds page = bh->b_page; 3191da177e4SLinus Torvalds if (uptodate) { 3201da177e4SLinus Torvalds set_buffer_uptodate(bh); 3211da177e4SLinus Torvalds } else { 3221da177e4SLinus Torvalds clear_buffer_uptodate(bh); 32308bafc03SKeith Mannthey if (!quiet_error(bh)) 3241da177e4SLinus Torvalds buffer_io_error(bh); 3251da177e4SLinus Torvalds SetPageError(page); 3261da177e4SLinus Torvalds } 3271da177e4SLinus Torvalds 3281da177e4SLinus Torvalds /* 3291da177e4SLinus Torvalds * Be _very_ careful from here on. Bad things can happen if 3301da177e4SLinus Torvalds * two buffer heads end IO at almost the same time and both 3311da177e4SLinus Torvalds * decide that the page is now completely done. 3321da177e4SLinus Torvalds */ 333a3972203SNick Piggin first = page_buffers(page); 334a3972203SNick Piggin local_irq_save(flags); 335a3972203SNick Piggin bit_spin_lock(BH_Uptodate_Lock, &first->b_state); 3361da177e4SLinus Torvalds clear_buffer_async_read(bh); 3371da177e4SLinus Torvalds unlock_buffer(bh); 3381da177e4SLinus Torvalds tmp = bh; 3391da177e4SLinus Torvalds do { 3401da177e4SLinus Torvalds if (!buffer_uptodate(tmp)) 3411da177e4SLinus Torvalds page_uptodate = 0; 3421da177e4SLinus Torvalds if (buffer_async_read(tmp)) { 3431da177e4SLinus Torvalds BUG_ON(!buffer_locked(tmp)); 3441da177e4SLinus Torvalds goto still_busy; 3451da177e4SLinus Torvalds } 3461da177e4SLinus Torvalds tmp = tmp->b_this_page; 3471da177e4SLinus Torvalds } while (tmp != bh); 348a3972203SNick Piggin bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 349a3972203SNick Piggin local_irq_restore(flags); 3501da177e4SLinus Torvalds 3511da177e4SLinus Torvalds /* 3521da177e4SLinus Torvalds * If none of the buffers had errors and they are all 3531da177e4SLinus Torvalds * uptodate then we can set the page uptodate. 3541da177e4SLinus Torvalds */ 3551da177e4SLinus Torvalds if (page_uptodate && !PageError(page)) 3561da177e4SLinus Torvalds SetPageUptodate(page); 3571da177e4SLinus Torvalds unlock_page(page); 3581da177e4SLinus Torvalds return; 3591da177e4SLinus Torvalds 3601da177e4SLinus Torvalds still_busy: 361a3972203SNick Piggin bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 362a3972203SNick Piggin local_irq_restore(flags); 3631da177e4SLinus Torvalds return; 3641da177e4SLinus Torvalds } 3651da177e4SLinus Torvalds 3661da177e4SLinus Torvalds /* 3671da177e4SLinus Torvalds * Completion handler for block_write_full_page() - pages which are unlocked 3681da177e4SLinus Torvalds * during I/O, and which have PageWriteback cleared upon I/O completion. 3691da177e4SLinus Torvalds */ 37035c80d5fSChris Mason void end_buffer_async_write(struct buffer_head *bh, int uptodate) 3711da177e4SLinus Torvalds { 3721da177e4SLinus Torvalds char b[BDEVNAME_SIZE]; 3731da177e4SLinus Torvalds unsigned long flags; 374a3972203SNick Piggin struct buffer_head *first; 3751da177e4SLinus Torvalds struct buffer_head *tmp; 3761da177e4SLinus Torvalds struct page *page; 3771da177e4SLinus Torvalds 3781da177e4SLinus Torvalds BUG_ON(!buffer_async_write(bh)); 3791da177e4SLinus Torvalds 3801da177e4SLinus Torvalds page = bh->b_page; 3811da177e4SLinus Torvalds if (uptodate) { 3821da177e4SLinus Torvalds set_buffer_uptodate(bh); 3831da177e4SLinus Torvalds } else { 38408bafc03SKeith Mannthey if (!quiet_error(bh)) { 3851da177e4SLinus Torvalds buffer_io_error(bh); 3861da177e4SLinus Torvalds printk(KERN_WARNING "lost page write due to " 3871da177e4SLinus Torvalds "I/O error on %s\n", 3881da177e4SLinus Torvalds bdevname(bh->b_bdev, b)); 3891da177e4SLinus Torvalds } 3901da177e4SLinus Torvalds set_bit(AS_EIO, &page->mapping->flags); 39158ff407bSJan Kara set_buffer_write_io_error(bh); 3921da177e4SLinus Torvalds clear_buffer_uptodate(bh); 3931da177e4SLinus Torvalds SetPageError(page); 3941da177e4SLinus Torvalds } 3951da177e4SLinus Torvalds 396a3972203SNick Piggin first = page_buffers(page); 397a3972203SNick Piggin local_irq_save(flags); 398a3972203SNick Piggin bit_spin_lock(BH_Uptodate_Lock, &first->b_state); 399a3972203SNick Piggin 4001da177e4SLinus Torvalds clear_buffer_async_write(bh); 4011da177e4SLinus Torvalds unlock_buffer(bh); 4021da177e4SLinus Torvalds tmp = bh->b_this_page; 4031da177e4SLinus Torvalds while (tmp != bh) { 4041da177e4SLinus Torvalds if (buffer_async_write(tmp)) { 4051da177e4SLinus Torvalds BUG_ON(!buffer_locked(tmp)); 4061da177e4SLinus Torvalds goto still_busy; 4071da177e4SLinus Torvalds } 4081da177e4SLinus Torvalds tmp = tmp->b_this_page; 4091da177e4SLinus Torvalds } 410a3972203SNick Piggin bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 411a3972203SNick Piggin local_irq_restore(flags); 4121da177e4SLinus Torvalds end_page_writeback(page); 4131da177e4SLinus Torvalds return; 4141da177e4SLinus Torvalds 4151da177e4SLinus Torvalds still_busy: 416a3972203SNick Piggin bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 417a3972203SNick Piggin local_irq_restore(flags); 4181da177e4SLinus Torvalds return; 4191da177e4SLinus Torvalds } 4201fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(end_buffer_async_write); 4211da177e4SLinus Torvalds 4221da177e4SLinus Torvalds /* 4231da177e4SLinus Torvalds * If a page's buffers are under async readin (end_buffer_async_read 4241da177e4SLinus Torvalds * completion) then there is a possibility that another thread of 4251da177e4SLinus Torvalds * control could lock one of the buffers after it has completed 4261da177e4SLinus Torvalds * but while some of the other buffers have not completed. This 4271da177e4SLinus Torvalds * locked buffer would confuse end_buffer_async_read() into not unlocking 4281da177e4SLinus Torvalds * the page. So the absence of BH_Async_Read tells end_buffer_async_read() 4291da177e4SLinus Torvalds * that this buffer is not under async I/O. 4301da177e4SLinus Torvalds * 4311da177e4SLinus Torvalds * The page comes unlocked when it has no locked buffer_async buffers 4321da177e4SLinus Torvalds * left. 4331da177e4SLinus Torvalds * 4341da177e4SLinus Torvalds * PageLocked prevents anyone starting new async I/O reads any of 4351da177e4SLinus Torvalds * the buffers. 4361da177e4SLinus Torvalds * 4371da177e4SLinus Torvalds * PageWriteback is used to prevent simultaneous writeout of the same 4381da177e4SLinus Torvalds * page. 4391da177e4SLinus Torvalds * 4401da177e4SLinus Torvalds * PageLocked prevents anyone from starting writeback of a page which is 4411da177e4SLinus Torvalds * under read I/O (PageWriteback is only ever set against a locked page). 4421da177e4SLinus Torvalds */ 4431da177e4SLinus Torvalds static void mark_buffer_async_read(struct buffer_head *bh) 4441da177e4SLinus Torvalds { 4451da177e4SLinus Torvalds bh->b_end_io = end_buffer_async_read; 4461da177e4SLinus Torvalds set_buffer_async_read(bh); 4471da177e4SLinus Torvalds } 4481da177e4SLinus Torvalds 4491fe72eaaSH Hartley Sweeten static void mark_buffer_async_write_endio(struct buffer_head *bh, 45035c80d5fSChris Mason bh_end_io_t *handler) 45135c80d5fSChris Mason { 45235c80d5fSChris Mason bh->b_end_io = handler; 45335c80d5fSChris Mason set_buffer_async_write(bh); 45435c80d5fSChris Mason } 45535c80d5fSChris Mason 4561da177e4SLinus Torvalds void mark_buffer_async_write(struct buffer_head *bh) 4571da177e4SLinus Torvalds { 45835c80d5fSChris Mason mark_buffer_async_write_endio(bh, end_buffer_async_write); 4591da177e4SLinus Torvalds } 4601da177e4SLinus Torvalds EXPORT_SYMBOL(mark_buffer_async_write); 4611da177e4SLinus Torvalds 4621da177e4SLinus Torvalds 4631da177e4SLinus Torvalds /* 4641da177e4SLinus Torvalds * fs/buffer.c contains helper functions for buffer-backed address space's 4651da177e4SLinus Torvalds * fsync functions. A common requirement for buffer-based filesystems is 4661da177e4SLinus Torvalds * that certain data from the backing blockdev needs to be written out for 4671da177e4SLinus Torvalds * a successful fsync(). For example, ext2 indirect blocks need to be 4681da177e4SLinus Torvalds * written back and waited upon before fsync() returns. 4691da177e4SLinus Torvalds * 4701da177e4SLinus Torvalds * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), 4711da177e4SLinus Torvalds * inode_has_buffers() and invalidate_inode_buffers() are provided for the 4721da177e4SLinus Torvalds * management of a list of dependent buffers at ->i_mapping->private_list. 4731da177e4SLinus Torvalds * 4741da177e4SLinus Torvalds * Locking is a little subtle: try_to_free_buffers() will remove buffers 4751da177e4SLinus Torvalds * from their controlling inode's queue when they are being freed. But 4761da177e4SLinus Torvalds * try_to_free_buffers() will be operating against the *blockdev* mapping 4771da177e4SLinus Torvalds * at the time, not against the S_ISREG file which depends on those buffers. 4781da177e4SLinus Torvalds * So the locking for private_list is via the private_lock in the address_space 4791da177e4SLinus Torvalds * which backs the buffers. Which is different from the address_space 4801da177e4SLinus Torvalds * against which the buffers are listed. So for a particular address_space, 4811da177e4SLinus Torvalds * mapping->private_lock does *not* protect mapping->private_list! In fact, 4821da177e4SLinus Torvalds * mapping->private_list will always be protected by the backing blockdev's 4831da177e4SLinus Torvalds * ->private_lock. 4841da177e4SLinus Torvalds * 4851da177e4SLinus Torvalds * Which introduces a requirement: all buffers on an address_space's 4861da177e4SLinus Torvalds * ->private_list must be from the same address_space: the blockdev's. 4871da177e4SLinus Torvalds * 4881da177e4SLinus Torvalds * address_spaces which do not place buffers at ->private_list via these 4891da177e4SLinus Torvalds * utility functions are free to use private_lock and private_list for 4901da177e4SLinus Torvalds * whatever they want. The only requirement is that list_empty(private_list) 4911da177e4SLinus Torvalds * be true at clear_inode() time. 4921da177e4SLinus Torvalds * 4931da177e4SLinus Torvalds * FIXME: clear_inode should not call invalidate_inode_buffers(). The 4941da177e4SLinus Torvalds * filesystems should do that. invalidate_inode_buffers() should just go 4951da177e4SLinus Torvalds * BUG_ON(!list_empty). 4961da177e4SLinus Torvalds * 4971da177e4SLinus Torvalds * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should 4981da177e4SLinus Torvalds * take an address_space, not an inode. And it should be called 4991da177e4SLinus Torvalds * mark_buffer_dirty_fsync() to clearly define why those buffers are being 5001da177e4SLinus Torvalds * queued up. 5011da177e4SLinus Torvalds * 5021da177e4SLinus Torvalds * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the 5031da177e4SLinus Torvalds * list if it is already on a list. Because if the buffer is on a list, 5041da177e4SLinus Torvalds * it *must* already be on the right one. If not, the filesystem is being 5051da177e4SLinus Torvalds * silly. This will save a ton of locking. But first we have to ensure 5061da177e4SLinus Torvalds * that buffers are taken *off* the old inode's list when they are freed 5071da177e4SLinus Torvalds * (presumably in truncate). That requires careful auditing of all 5081da177e4SLinus Torvalds * filesystems (do it inside bforget()). It could also be done by bringing 5091da177e4SLinus Torvalds * b_inode back. 5101da177e4SLinus Torvalds */ 5111da177e4SLinus Torvalds 5121da177e4SLinus Torvalds /* 5131da177e4SLinus Torvalds * The buffer's backing address_space's private_lock must be held 5141da177e4SLinus Torvalds */ 515dbacefc9SThomas Petazzoni static void __remove_assoc_queue(struct buffer_head *bh) 5161da177e4SLinus Torvalds { 5171da177e4SLinus Torvalds list_del_init(&bh->b_assoc_buffers); 51858ff407bSJan Kara WARN_ON(!bh->b_assoc_map); 51958ff407bSJan Kara if (buffer_write_io_error(bh)) 52058ff407bSJan Kara set_bit(AS_EIO, &bh->b_assoc_map->flags); 52158ff407bSJan Kara bh->b_assoc_map = NULL; 5221da177e4SLinus Torvalds } 5231da177e4SLinus Torvalds 5241da177e4SLinus Torvalds int inode_has_buffers(struct inode *inode) 5251da177e4SLinus Torvalds { 5261da177e4SLinus Torvalds return !list_empty(&inode->i_data.private_list); 5271da177e4SLinus Torvalds } 5281da177e4SLinus Torvalds 5291da177e4SLinus Torvalds /* 5301da177e4SLinus Torvalds * osync is designed to support O_SYNC io. It waits synchronously for 5311da177e4SLinus Torvalds * all already-submitted IO to complete, but does not queue any new 5321da177e4SLinus Torvalds * writes to the disk. 5331da177e4SLinus Torvalds * 5341da177e4SLinus Torvalds * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as 5351da177e4SLinus Torvalds * you dirty the buffers, and then use osync_inode_buffers to wait for 5361da177e4SLinus Torvalds * completion. Any other dirty buffers which are not yet queued for 5371da177e4SLinus Torvalds * write will not be flushed to disk by the osync. 5381da177e4SLinus Torvalds */ 5391da177e4SLinus Torvalds static int osync_buffers_list(spinlock_t *lock, struct list_head *list) 5401da177e4SLinus Torvalds { 5411da177e4SLinus Torvalds struct buffer_head *bh; 5421da177e4SLinus Torvalds struct list_head *p; 5431da177e4SLinus Torvalds int err = 0; 5441da177e4SLinus Torvalds 5451da177e4SLinus Torvalds spin_lock(lock); 5461da177e4SLinus Torvalds repeat: 5471da177e4SLinus Torvalds list_for_each_prev(p, list) { 5481da177e4SLinus Torvalds bh = BH_ENTRY(p); 5491da177e4SLinus Torvalds if (buffer_locked(bh)) { 5501da177e4SLinus Torvalds get_bh(bh); 5511da177e4SLinus Torvalds spin_unlock(lock); 5521da177e4SLinus Torvalds wait_on_buffer(bh); 5531da177e4SLinus Torvalds if (!buffer_uptodate(bh)) 5541da177e4SLinus Torvalds err = -EIO; 5551da177e4SLinus Torvalds brelse(bh); 5561da177e4SLinus Torvalds spin_lock(lock); 5571da177e4SLinus Torvalds goto repeat; 5581da177e4SLinus Torvalds } 5591da177e4SLinus Torvalds } 5601da177e4SLinus Torvalds spin_unlock(lock); 5611da177e4SLinus Torvalds return err; 5621da177e4SLinus Torvalds } 5631da177e4SLinus Torvalds 56401a05b33SAl Viro static void do_thaw_one(struct super_block *sb, void *unused) 565c2d75438SEric Sandeen { 566c2d75438SEric Sandeen char b[BDEVNAME_SIZE]; 567c2d75438SEric Sandeen while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) 568c2d75438SEric Sandeen printk(KERN_WARNING "Emergency Thaw on %s\n", 569c2d75438SEric Sandeen bdevname(sb->s_bdev, b)); 570c2d75438SEric Sandeen } 57101a05b33SAl Viro 57201a05b33SAl Viro static void do_thaw_all(struct work_struct *work) 57301a05b33SAl Viro { 57401a05b33SAl Viro iterate_supers(do_thaw_one, NULL); 575053c525fSJens Axboe kfree(work); 576c2d75438SEric Sandeen printk(KERN_WARNING "Emergency Thaw complete\n"); 577c2d75438SEric Sandeen } 578c2d75438SEric Sandeen 579c2d75438SEric Sandeen /** 580c2d75438SEric Sandeen * emergency_thaw_all -- forcibly thaw every frozen filesystem 581c2d75438SEric Sandeen * 582c2d75438SEric Sandeen * Used for emergency unfreeze of all filesystems via SysRq 583c2d75438SEric Sandeen */ 584c2d75438SEric Sandeen void emergency_thaw_all(void) 585c2d75438SEric Sandeen { 586053c525fSJens Axboe struct work_struct *work; 587053c525fSJens Axboe 588053c525fSJens Axboe work = kmalloc(sizeof(*work), GFP_ATOMIC); 589053c525fSJens Axboe if (work) { 590053c525fSJens Axboe INIT_WORK(work, do_thaw_all); 591053c525fSJens Axboe schedule_work(work); 592053c525fSJens Axboe } 593c2d75438SEric Sandeen } 594c2d75438SEric Sandeen 5951da177e4SLinus Torvalds /** 59678a4a50aSRandy Dunlap * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers 59767be2dd1SMartin Waitz * @mapping: the mapping which wants those buffers written 5981da177e4SLinus Torvalds * 5991da177e4SLinus Torvalds * Starts I/O against the buffers at mapping->private_list, and waits upon 6001da177e4SLinus Torvalds * that I/O. 6011da177e4SLinus Torvalds * 60267be2dd1SMartin Waitz * Basically, this is a convenience function for fsync(). 60367be2dd1SMartin Waitz * @mapping is a file or directory which needs those buffers to be written for 60467be2dd1SMartin Waitz * a successful fsync(). 6051da177e4SLinus Torvalds */ 6061da177e4SLinus Torvalds int sync_mapping_buffers(struct address_space *mapping) 6071da177e4SLinus Torvalds { 6081da177e4SLinus Torvalds struct address_space *buffer_mapping = mapping->assoc_mapping; 6091da177e4SLinus Torvalds 6101da177e4SLinus Torvalds if (buffer_mapping == NULL || list_empty(&mapping->private_list)) 6111da177e4SLinus Torvalds return 0; 6121da177e4SLinus Torvalds 6131da177e4SLinus Torvalds return fsync_buffers_list(&buffer_mapping->private_lock, 6141da177e4SLinus Torvalds &mapping->private_list); 6151da177e4SLinus Torvalds } 6161da177e4SLinus Torvalds EXPORT_SYMBOL(sync_mapping_buffers); 6171da177e4SLinus Torvalds 6181da177e4SLinus Torvalds /* 6191da177e4SLinus Torvalds * Called when we've recently written block `bblock', and it is known that 6201da177e4SLinus Torvalds * `bblock' was for a buffer_boundary() buffer. This means that the block at 6211da177e4SLinus Torvalds * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's 6221da177e4SLinus Torvalds * dirty, schedule it for IO. So that indirects merge nicely with their data. 6231da177e4SLinus Torvalds */ 6241da177e4SLinus Torvalds void write_boundary_block(struct block_device *bdev, 6251da177e4SLinus Torvalds sector_t bblock, unsigned blocksize) 6261da177e4SLinus Torvalds { 6271da177e4SLinus Torvalds struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); 6281da177e4SLinus Torvalds if (bh) { 6291da177e4SLinus Torvalds if (buffer_dirty(bh)) 6301da177e4SLinus Torvalds ll_rw_block(WRITE, 1, &bh); 6311da177e4SLinus Torvalds put_bh(bh); 6321da177e4SLinus Torvalds } 6331da177e4SLinus Torvalds } 6341da177e4SLinus Torvalds 6351da177e4SLinus Torvalds void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) 6361da177e4SLinus Torvalds { 6371da177e4SLinus Torvalds struct address_space *mapping = inode->i_mapping; 6381da177e4SLinus Torvalds struct address_space *buffer_mapping = bh->b_page->mapping; 6391da177e4SLinus Torvalds 6401da177e4SLinus Torvalds mark_buffer_dirty(bh); 6411da177e4SLinus Torvalds if (!mapping->assoc_mapping) { 6421da177e4SLinus Torvalds mapping->assoc_mapping = buffer_mapping; 6431da177e4SLinus Torvalds } else { 644e827f923SEric Sesterhenn BUG_ON(mapping->assoc_mapping != buffer_mapping); 6451da177e4SLinus Torvalds } 646535ee2fbSJan Kara if (!bh->b_assoc_map) { 6471da177e4SLinus Torvalds spin_lock(&buffer_mapping->private_lock); 6481da177e4SLinus Torvalds list_move_tail(&bh->b_assoc_buffers, 6491da177e4SLinus Torvalds &mapping->private_list); 65058ff407bSJan Kara bh->b_assoc_map = mapping; 6511da177e4SLinus Torvalds spin_unlock(&buffer_mapping->private_lock); 6521da177e4SLinus Torvalds } 6531da177e4SLinus Torvalds } 6541da177e4SLinus Torvalds EXPORT_SYMBOL(mark_buffer_dirty_inode); 6551da177e4SLinus Torvalds 6561da177e4SLinus Torvalds /* 657787d2214SNick Piggin * Mark the page dirty, and set it dirty in the radix tree, and mark the inode 658787d2214SNick Piggin * dirty. 659787d2214SNick Piggin * 660787d2214SNick Piggin * If warn is true, then emit a warning if the page is not uptodate and has 661787d2214SNick Piggin * not been truncated. 662787d2214SNick Piggin */ 663a8e7d49aSLinus Torvalds static void __set_page_dirty(struct page *page, 664787d2214SNick Piggin struct address_space *mapping, int warn) 665787d2214SNick Piggin { 66619fd6231SNick Piggin spin_lock_irq(&mapping->tree_lock); 667787d2214SNick Piggin if (page->mapping) { /* Race with truncate? */ 668787d2214SNick Piggin WARN_ON_ONCE(warn && !PageUptodate(page)); 669e3a7cca1SEdward Shishkin account_page_dirtied(page, mapping); 670787d2214SNick Piggin radix_tree_tag_set(&mapping->page_tree, 671787d2214SNick Piggin page_index(page), PAGECACHE_TAG_DIRTY); 672787d2214SNick Piggin } 67319fd6231SNick Piggin spin_unlock_irq(&mapping->tree_lock); 674787d2214SNick Piggin __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); 675787d2214SNick Piggin } 676787d2214SNick Piggin 677787d2214SNick Piggin /* 6781da177e4SLinus Torvalds * Add a page to the dirty page list. 6791da177e4SLinus Torvalds * 6801da177e4SLinus Torvalds * It is a sad fact of life that this function is called from several places 6811da177e4SLinus Torvalds * deeply under spinlocking. It may not sleep. 6821da177e4SLinus Torvalds * 6831da177e4SLinus Torvalds * If the page has buffers, the uptodate buffers are set dirty, to preserve 6841da177e4SLinus Torvalds * dirty-state coherency between the page and the buffers. It the page does 6851da177e4SLinus Torvalds * not have buffers then when they are later attached they will all be set 6861da177e4SLinus Torvalds * dirty. 6871da177e4SLinus Torvalds * 6881da177e4SLinus Torvalds * The buffers are dirtied before the page is dirtied. There's a small race 6891da177e4SLinus Torvalds * window in which a writepage caller may see the page cleanness but not the 6901da177e4SLinus Torvalds * buffer dirtiness. That's fine. If this code were to set the page dirty 6911da177e4SLinus Torvalds * before the buffers, a concurrent writepage caller could clear the page dirty 6921da177e4SLinus Torvalds * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean 6931da177e4SLinus Torvalds * page on the dirty page list. 6941da177e4SLinus Torvalds * 6951da177e4SLinus Torvalds * We use private_lock to lock against try_to_free_buffers while using the 6961da177e4SLinus Torvalds * page's buffer list. Also use this to protect against clean buffers being 6971da177e4SLinus Torvalds * added to the page after it was set dirty. 6981da177e4SLinus Torvalds * 6991da177e4SLinus Torvalds * FIXME: may need to call ->reservepage here as well. That's rather up to the 7001da177e4SLinus Torvalds * address_space though. 7011da177e4SLinus Torvalds */ 7021da177e4SLinus Torvalds int __set_page_dirty_buffers(struct page *page) 7031da177e4SLinus Torvalds { 704a8e7d49aSLinus Torvalds int newly_dirty; 705787d2214SNick Piggin struct address_space *mapping = page_mapping(page); 706ebf7a227SNick Piggin 707ebf7a227SNick Piggin if (unlikely(!mapping)) 708ebf7a227SNick Piggin return !TestSetPageDirty(page); 7091da177e4SLinus Torvalds 7101da177e4SLinus Torvalds spin_lock(&mapping->private_lock); 7111da177e4SLinus Torvalds if (page_has_buffers(page)) { 7121da177e4SLinus Torvalds struct buffer_head *head = page_buffers(page); 7131da177e4SLinus Torvalds struct buffer_head *bh = head; 7141da177e4SLinus Torvalds 7151da177e4SLinus Torvalds do { 7161da177e4SLinus Torvalds set_buffer_dirty(bh); 7171da177e4SLinus Torvalds bh = bh->b_this_page; 7181da177e4SLinus Torvalds } while (bh != head); 7191da177e4SLinus Torvalds } 720a8e7d49aSLinus Torvalds newly_dirty = !TestSetPageDirty(page); 7211da177e4SLinus Torvalds spin_unlock(&mapping->private_lock); 7221da177e4SLinus Torvalds 723a8e7d49aSLinus Torvalds if (newly_dirty) 724a8e7d49aSLinus Torvalds __set_page_dirty(page, mapping, 1); 725a8e7d49aSLinus Torvalds return newly_dirty; 7261da177e4SLinus Torvalds } 7271da177e4SLinus Torvalds EXPORT_SYMBOL(__set_page_dirty_buffers); 7281da177e4SLinus Torvalds 7291da177e4SLinus Torvalds /* 7301da177e4SLinus Torvalds * Write out and wait upon a list of buffers. 7311da177e4SLinus Torvalds * 7321da177e4SLinus Torvalds * We have conflicting pressures: we want to make sure that all 7331da177e4SLinus Torvalds * initially dirty buffers get waited on, but that any subsequently 7341da177e4SLinus Torvalds * dirtied buffers don't. After all, we don't want fsync to last 7351da177e4SLinus Torvalds * forever if somebody is actively writing to the file. 7361da177e4SLinus Torvalds * 7371da177e4SLinus Torvalds * Do this in two main stages: first we copy dirty buffers to a 7381da177e4SLinus Torvalds * temporary inode list, queueing the writes as we go. Then we clean 7391da177e4SLinus Torvalds * up, waiting for those writes to complete. 7401da177e4SLinus Torvalds * 7411da177e4SLinus Torvalds * During this second stage, any subsequent updates to the file may end 7421da177e4SLinus Torvalds * up refiling the buffer on the original inode's dirty list again, so 7431da177e4SLinus Torvalds * there is a chance we will end up with a buffer queued for write but 7441da177e4SLinus Torvalds * not yet completed on that list. So, as a final cleanup we go through 7451da177e4SLinus Torvalds * the osync code to catch these locked, dirty buffers without requeuing 7461da177e4SLinus Torvalds * any newly dirty buffers for write. 7471da177e4SLinus Torvalds */ 7481da177e4SLinus Torvalds static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) 7491da177e4SLinus Torvalds { 7501da177e4SLinus Torvalds struct buffer_head *bh; 7511da177e4SLinus Torvalds struct list_head tmp; 7529cf6b720SJens Axboe struct address_space *mapping, *prev_mapping = NULL; 7531da177e4SLinus Torvalds int err = 0, err2; 7541da177e4SLinus Torvalds 7551da177e4SLinus Torvalds INIT_LIST_HEAD(&tmp); 7561da177e4SLinus Torvalds 7571da177e4SLinus Torvalds spin_lock(lock); 7581da177e4SLinus Torvalds while (!list_empty(list)) { 7591da177e4SLinus Torvalds bh = BH_ENTRY(list->next); 760535ee2fbSJan Kara mapping = bh->b_assoc_map; 76158ff407bSJan Kara __remove_assoc_queue(bh); 762535ee2fbSJan Kara /* Avoid race with mark_buffer_dirty_inode() which does 763535ee2fbSJan Kara * a lockless check and we rely on seeing the dirty bit */ 764535ee2fbSJan Kara smp_mb(); 7651da177e4SLinus Torvalds if (buffer_dirty(bh) || buffer_locked(bh)) { 7661da177e4SLinus Torvalds list_add(&bh->b_assoc_buffers, &tmp); 767535ee2fbSJan Kara bh->b_assoc_map = mapping; 7681da177e4SLinus Torvalds if (buffer_dirty(bh)) { 7691da177e4SLinus Torvalds get_bh(bh); 7701da177e4SLinus Torvalds spin_unlock(lock); 7711da177e4SLinus Torvalds /* 7721da177e4SLinus Torvalds * Ensure any pending I/O completes so that 773*9cb569d6SChristoph Hellwig * write_dirty_buffer() actually writes the 774*9cb569d6SChristoph Hellwig * current contents - it is a noop if I/O is 775*9cb569d6SChristoph Hellwig * still in flight on potentially older 776*9cb569d6SChristoph Hellwig * contents. 7771da177e4SLinus Torvalds */ 778*9cb569d6SChristoph Hellwig write_dirty_buffer(bh, WRITE_SYNC_PLUG); 7799cf6b720SJens Axboe 7809cf6b720SJens Axboe /* 7819cf6b720SJens Axboe * Kick off IO for the previous mapping. Note 7829cf6b720SJens Axboe * that we will not run the very last mapping, 7839cf6b720SJens Axboe * wait_on_buffer() will do that for us 7849cf6b720SJens Axboe * through sync_buffer(). 7859cf6b720SJens Axboe */ 7869cf6b720SJens Axboe if (prev_mapping && prev_mapping != mapping) 7879cf6b720SJens Axboe blk_run_address_space(prev_mapping); 7889cf6b720SJens Axboe prev_mapping = mapping; 7899cf6b720SJens Axboe 7901da177e4SLinus Torvalds brelse(bh); 7911da177e4SLinus Torvalds spin_lock(lock); 7921da177e4SLinus Torvalds } 7931da177e4SLinus Torvalds } 7941da177e4SLinus Torvalds } 7951da177e4SLinus Torvalds 7961da177e4SLinus Torvalds while (!list_empty(&tmp)) { 7971da177e4SLinus Torvalds bh = BH_ENTRY(tmp.prev); 7981da177e4SLinus Torvalds get_bh(bh); 799535ee2fbSJan Kara mapping = bh->b_assoc_map; 800535ee2fbSJan Kara __remove_assoc_queue(bh); 801535ee2fbSJan Kara /* Avoid race with mark_buffer_dirty_inode() which does 802535ee2fbSJan Kara * a lockless check and we rely on seeing the dirty bit */ 803535ee2fbSJan Kara smp_mb(); 804535ee2fbSJan Kara if (buffer_dirty(bh)) { 805535ee2fbSJan Kara list_add(&bh->b_assoc_buffers, 806e3892296SJan Kara &mapping->private_list); 807535ee2fbSJan Kara bh->b_assoc_map = mapping; 808535ee2fbSJan Kara } 8091da177e4SLinus Torvalds spin_unlock(lock); 8101da177e4SLinus Torvalds wait_on_buffer(bh); 8111da177e4SLinus Torvalds if (!buffer_uptodate(bh)) 8121da177e4SLinus Torvalds err = -EIO; 8131da177e4SLinus Torvalds brelse(bh); 8141da177e4SLinus Torvalds spin_lock(lock); 8151da177e4SLinus Torvalds } 8161da177e4SLinus Torvalds 8171da177e4SLinus Torvalds spin_unlock(lock); 8181da177e4SLinus Torvalds err2 = osync_buffers_list(lock, list); 8191da177e4SLinus Torvalds if (err) 8201da177e4SLinus Torvalds return err; 8211da177e4SLinus Torvalds else 8221da177e4SLinus Torvalds return err2; 8231da177e4SLinus Torvalds } 8241da177e4SLinus Torvalds 8251da177e4SLinus Torvalds /* 8261da177e4SLinus Torvalds * Invalidate any and all dirty buffers on a given inode. We are 8271da177e4SLinus Torvalds * probably unmounting the fs, but that doesn't mean we have already 8281da177e4SLinus Torvalds * done a sync(). Just drop the buffers from the inode list. 8291da177e4SLinus Torvalds * 8301da177e4SLinus Torvalds * NOTE: we take the inode's blockdev's mapping's private_lock. Which 8311da177e4SLinus Torvalds * assumes that all the buffers are against the blockdev. Not true 8321da177e4SLinus Torvalds * for reiserfs. 8331da177e4SLinus Torvalds */ 8341da177e4SLinus Torvalds void invalidate_inode_buffers(struct inode *inode) 8351da177e4SLinus Torvalds { 8361da177e4SLinus Torvalds if (inode_has_buffers(inode)) { 8371da177e4SLinus Torvalds struct address_space *mapping = &inode->i_data; 8381da177e4SLinus Torvalds struct list_head *list = &mapping->private_list; 8391da177e4SLinus Torvalds struct address_space *buffer_mapping = mapping->assoc_mapping; 8401da177e4SLinus Torvalds 8411da177e4SLinus Torvalds spin_lock(&buffer_mapping->private_lock); 8421da177e4SLinus Torvalds while (!list_empty(list)) 8431da177e4SLinus Torvalds __remove_assoc_queue(BH_ENTRY(list->next)); 8441da177e4SLinus Torvalds spin_unlock(&buffer_mapping->private_lock); 8451da177e4SLinus Torvalds } 8461da177e4SLinus Torvalds } 84752b19ac9SJan Kara EXPORT_SYMBOL(invalidate_inode_buffers); 8481da177e4SLinus Torvalds 8491da177e4SLinus Torvalds /* 8501da177e4SLinus Torvalds * Remove any clean buffers from the inode's buffer list. This is called 8511da177e4SLinus Torvalds * when we're trying to free the inode itself. Those buffers can pin it. 8521da177e4SLinus Torvalds * 8531da177e4SLinus Torvalds * Returns true if all buffers were removed. 8541da177e4SLinus Torvalds */ 8551da177e4SLinus Torvalds int remove_inode_buffers(struct inode *inode) 8561da177e4SLinus Torvalds { 8571da177e4SLinus Torvalds int ret = 1; 8581da177e4SLinus Torvalds 8591da177e4SLinus Torvalds if (inode_has_buffers(inode)) { 8601da177e4SLinus Torvalds struct address_space *mapping = &inode->i_data; 8611da177e4SLinus Torvalds struct list_head *list = &mapping->private_list; 8621da177e4SLinus Torvalds struct address_space *buffer_mapping = mapping->assoc_mapping; 8631da177e4SLinus Torvalds 8641da177e4SLinus Torvalds spin_lock(&buffer_mapping->private_lock); 8651da177e4SLinus Torvalds while (!list_empty(list)) { 8661da177e4SLinus Torvalds struct buffer_head *bh = BH_ENTRY(list->next); 8671da177e4SLinus Torvalds if (buffer_dirty(bh)) { 8681da177e4SLinus Torvalds ret = 0; 8691da177e4SLinus Torvalds break; 8701da177e4SLinus Torvalds } 8711da177e4SLinus Torvalds __remove_assoc_queue(bh); 8721da177e4SLinus Torvalds } 8731da177e4SLinus Torvalds spin_unlock(&buffer_mapping->private_lock); 8741da177e4SLinus Torvalds } 8751da177e4SLinus Torvalds return ret; 8761da177e4SLinus Torvalds } 8771da177e4SLinus Torvalds 8781da177e4SLinus Torvalds /* 8791da177e4SLinus Torvalds * Create the appropriate buffers when given a page for data area and 8801da177e4SLinus Torvalds * the size of each buffer.. Use the bh->b_this_page linked list to 8811da177e4SLinus Torvalds * follow the buffers created. Return NULL if unable to create more 8821da177e4SLinus Torvalds * buffers. 8831da177e4SLinus Torvalds * 8841da177e4SLinus Torvalds * The retry flag is used to differentiate async IO (paging, swapping) 8851da177e4SLinus Torvalds * which may not fail from ordinary buffer allocations. 8861da177e4SLinus Torvalds */ 8871da177e4SLinus Torvalds struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 8881da177e4SLinus Torvalds int retry) 8891da177e4SLinus Torvalds { 8901da177e4SLinus Torvalds struct buffer_head *bh, *head; 8911da177e4SLinus Torvalds long offset; 8921da177e4SLinus Torvalds 8931da177e4SLinus Torvalds try_again: 8941da177e4SLinus Torvalds head = NULL; 8951da177e4SLinus Torvalds offset = PAGE_SIZE; 8961da177e4SLinus Torvalds while ((offset -= size) >= 0) { 8971da177e4SLinus Torvalds bh = alloc_buffer_head(GFP_NOFS); 8981da177e4SLinus Torvalds if (!bh) 8991da177e4SLinus Torvalds goto no_grow; 9001da177e4SLinus Torvalds 9011da177e4SLinus Torvalds bh->b_bdev = NULL; 9021da177e4SLinus Torvalds bh->b_this_page = head; 9031da177e4SLinus Torvalds bh->b_blocknr = -1; 9041da177e4SLinus Torvalds head = bh; 9051da177e4SLinus Torvalds 9061da177e4SLinus Torvalds bh->b_state = 0; 9071da177e4SLinus Torvalds atomic_set(&bh->b_count, 0); 908fc5cd582SChris Mason bh->b_private = NULL; 9091da177e4SLinus Torvalds bh->b_size = size; 9101da177e4SLinus Torvalds 9111da177e4SLinus Torvalds /* Link the buffer to its page */ 9121da177e4SLinus Torvalds set_bh_page(bh, page, offset); 9131da177e4SLinus Torvalds 91401ffe339SNathan Scott init_buffer(bh, NULL, NULL); 9151da177e4SLinus Torvalds } 9161da177e4SLinus Torvalds return head; 9171da177e4SLinus Torvalds /* 9181da177e4SLinus Torvalds * In case anything failed, we just free everything we got. 9191da177e4SLinus Torvalds */ 9201da177e4SLinus Torvalds no_grow: 9211da177e4SLinus Torvalds if (head) { 9221da177e4SLinus Torvalds do { 9231da177e4SLinus Torvalds bh = head; 9241da177e4SLinus Torvalds head = head->b_this_page; 9251da177e4SLinus Torvalds free_buffer_head(bh); 9261da177e4SLinus Torvalds } while (head); 9271da177e4SLinus Torvalds } 9281da177e4SLinus Torvalds 9291da177e4SLinus Torvalds /* 9301da177e4SLinus Torvalds * Return failure for non-async IO requests. Async IO requests 9311da177e4SLinus Torvalds * are not allowed to fail, so we have to wait until buffer heads 9321da177e4SLinus Torvalds * become available. But we don't want tasks sleeping with 9331da177e4SLinus Torvalds * partially complete buffers, so all were released above. 9341da177e4SLinus Torvalds */ 9351da177e4SLinus Torvalds if (!retry) 9361da177e4SLinus Torvalds return NULL; 9371da177e4SLinus Torvalds 9381da177e4SLinus Torvalds /* We're _really_ low on memory. Now we just 9391da177e4SLinus Torvalds * wait for old buffer heads to become free due to 9401da177e4SLinus Torvalds * finishing IO. Since this is an async request and 9411da177e4SLinus Torvalds * the reserve list is empty, we're sure there are 9421da177e4SLinus Torvalds * async buffer heads in use. 9431da177e4SLinus Torvalds */ 9441da177e4SLinus Torvalds free_more_memory(); 9451da177e4SLinus Torvalds goto try_again; 9461da177e4SLinus Torvalds } 9471da177e4SLinus Torvalds EXPORT_SYMBOL_GPL(alloc_page_buffers); 9481da177e4SLinus Torvalds 9491da177e4SLinus Torvalds static inline void 9501da177e4SLinus Torvalds link_dev_buffers(struct page *page, struct buffer_head *head) 9511da177e4SLinus Torvalds { 9521da177e4SLinus Torvalds struct buffer_head *bh, *tail; 9531da177e4SLinus Torvalds 9541da177e4SLinus Torvalds bh = head; 9551da177e4SLinus Torvalds do { 9561da177e4SLinus Torvalds tail = bh; 9571da177e4SLinus Torvalds bh = bh->b_this_page; 9581da177e4SLinus Torvalds } while (bh); 9591da177e4SLinus Torvalds tail->b_this_page = head; 9601da177e4SLinus Torvalds attach_page_buffers(page, head); 9611da177e4SLinus Torvalds } 9621da177e4SLinus Torvalds 9631da177e4SLinus Torvalds /* 9641da177e4SLinus Torvalds * Initialise the state of a blockdev page's buffers. 9651da177e4SLinus Torvalds */ 9661da177e4SLinus Torvalds static void 9671da177e4SLinus Torvalds init_page_buffers(struct page *page, struct block_device *bdev, 9681da177e4SLinus Torvalds sector_t block, int size) 9691da177e4SLinus Torvalds { 9701da177e4SLinus Torvalds struct buffer_head *head = page_buffers(page); 9711da177e4SLinus Torvalds struct buffer_head *bh = head; 9721da177e4SLinus Torvalds int uptodate = PageUptodate(page); 9731da177e4SLinus Torvalds 9741da177e4SLinus Torvalds do { 9751da177e4SLinus Torvalds if (!buffer_mapped(bh)) { 9761da177e4SLinus Torvalds init_buffer(bh, NULL, NULL); 9771da177e4SLinus Torvalds bh->b_bdev = bdev; 9781da177e4SLinus Torvalds bh->b_blocknr = block; 9791da177e4SLinus Torvalds if (uptodate) 9801da177e4SLinus Torvalds set_buffer_uptodate(bh); 9811da177e4SLinus Torvalds set_buffer_mapped(bh); 9821da177e4SLinus Torvalds } 9831da177e4SLinus Torvalds block++; 9841da177e4SLinus Torvalds bh = bh->b_this_page; 9851da177e4SLinus Torvalds } while (bh != head); 9861da177e4SLinus Torvalds } 9871da177e4SLinus Torvalds 9881da177e4SLinus Torvalds /* 9891da177e4SLinus Torvalds * Create the page-cache page that contains the requested block. 9901da177e4SLinus Torvalds * 9911da177e4SLinus Torvalds * This is user purely for blockdev mappings. 9921da177e4SLinus Torvalds */ 9931da177e4SLinus Torvalds static struct page * 9941da177e4SLinus Torvalds grow_dev_page(struct block_device *bdev, sector_t block, 9951da177e4SLinus Torvalds pgoff_t index, int size) 9961da177e4SLinus Torvalds { 9971da177e4SLinus Torvalds struct inode *inode = bdev->bd_inode; 9981da177e4SLinus Torvalds struct page *page; 9991da177e4SLinus Torvalds struct buffer_head *bh; 10001da177e4SLinus Torvalds 1001ea125892SChristoph Lameter page = find_or_create_page(inode->i_mapping, index, 1002769848c0SMel Gorman (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); 10031da177e4SLinus Torvalds if (!page) 10041da177e4SLinus Torvalds return NULL; 10051da177e4SLinus Torvalds 1006e827f923SEric Sesterhenn BUG_ON(!PageLocked(page)); 10071da177e4SLinus Torvalds 10081da177e4SLinus Torvalds if (page_has_buffers(page)) { 10091da177e4SLinus Torvalds bh = page_buffers(page); 10101da177e4SLinus Torvalds if (bh->b_size == size) { 10111da177e4SLinus Torvalds init_page_buffers(page, bdev, block, size); 10121da177e4SLinus Torvalds return page; 10131da177e4SLinus Torvalds } 10141da177e4SLinus Torvalds if (!try_to_free_buffers(page)) 10151da177e4SLinus Torvalds goto failed; 10161da177e4SLinus Torvalds } 10171da177e4SLinus Torvalds 10181da177e4SLinus Torvalds /* 10191da177e4SLinus Torvalds * Allocate some buffers for this page 10201da177e4SLinus Torvalds */ 10211da177e4SLinus Torvalds bh = alloc_page_buffers(page, size, 0); 10221da177e4SLinus Torvalds if (!bh) 10231da177e4SLinus Torvalds goto failed; 10241da177e4SLinus Torvalds 10251da177e4SLinus Torvalds /* 10261da177e4SLinus Torvalds * Link the page to the buffers and initialise them. Take the 10271da177e4SLinus Torvalds * lock to be atomic wrt __find_get_block(), which does not 10281da177e4SLinus Torvalds * run under the page lock. 10291da177e4SLinus Torvalds */ 10301da177e4SLinus Torvalds spin_lock(&inode->i_mapping->private_lock); 10311da177e4SLinus Torvalds link_dev_buffers(page, bh); 10321da177e4SLinus Torvalds init_page_buffers(page, bdev, block, size); 10331da177e4SLinus Torvalds spin_unlock(&inode->i_mapping->private_lock); 10341da177e4SLinus Torvalds return page; 10351da177e4SLinus Torvalds 10361da177e4SLinus Torvalds failed: 10371da177e4SLinus Torvalds BUG(); 10381da177e4SLinus Torvalds unlock_page(page); 10391da177e4SLinus Torvalds page_cache_release(page); 10401da177e4SLinus Torvalds return NULL; 10411da177e4SLinus Torvalds } 10421da177e4SLinus Torvalds 10431da177e4SLinus Torvalds /* 10441da177e4SLinus Torvalds * Create buffers for the specified block device block's page. If 10451da177e4SLinus Torvalds * that page was dirty, the buffers are set dirty also. 10461da177e4SLinus Torvalds */ 1047858119e1SArjan van de Ven static int 10481da177e4SLinus Torvalds grow_buffers(struct block_device *bdev, sector_t block, int size) 10491da177e4SLinus Torvalds { 10501da177e4SLinus Torvalds struct page *page; 10511da177e4SLinus Torvalds pgoff_t index; 10521da177e4SLinus Torvalds int sizebits; 10531da177e4SLinus Torvalds 10541da177e4SLinus Torvalds sizebits = -1; 10551da177e4SLinus Torvalds do { 10561da177e4SLinus Torvalds sizebits++; 10571da177e4SLinus Torvalds } while ((size << sizebits) < PAGE_SIZE); 10581da177e4SLinus Torvalds 10591da177e4SLinus Torvalds index = block >> sizebits; 10601da177e4SLinus Torvalds 1061e5657933SAndrew Morton /* 1062e5657933SAndrew Morton * Check for a block which wants to lie outside our maximum possible 1063e5657933SAndrew Morton * pagecache index. (this comparison is done using sector_t types). 1064e5657933SAndrew Morton */ 1065e5657933SAndrew Morton if (unlikely(index != block >> sizebits)) { 1066e5657933SAndrew Morton char b[BDEVNAME_SIZE]; 1067e5657933SAndrew Morton 1068e5657933SAndrew Morton printk(KERN_ERR "%s: requested out-of-range block %llu for " 1069e5657933SAndrew Morton "device %s\n", 10708e24eea7SHarvey Harrison __func__, (unsigned long long)block, 1071e5657933SAndrew Morton bdevname(bdev, b)); 1072e5657933SAndrew Morton return -EIO; 1073e5657933SAndrew Morton } 1074e5657933SAndrew Morton block = index << sizebits; 10751da177e4SLinus Torvalds /* Create a page with the proper size buffers.. */ 10761da177e4SLinus Torvalds page = grow_dev_page(bdev, block, index, size); 10771da177e4SLinus Torvalds if (!page) 10781da177e4SLinus Torvalds return 0; 10791da177e4SLinus Torvalds unlock_page(page); 10801da177e4SLinus Torvalds page_cache_release(page); 10811da177e4SLinus Torvalds return 1; 10821da177e4SLinus Torvalds } 10831da177e4SLinus Torvalds 108475c96f85SAdrian Bunk static struct buffer_head * 10851da177e4SLinus Torvalds __getblk_slow(struct block_device *bdev, sector_t block, int size) 10861da177e4SLinus Torvalds { 10871da177e4SLinus Torvalds /* Size must be multiple of hard sectorsize */ 1088e1defc4fSMartin K. Petersen if (unlikely(size & (bdev_logical_block_size(bdev)-1) || 10891da177e4SLinus Torvalds (size < 512 || size > PAGE_SIZE))) { 10901da177e4SLinus Torvalds printk(KERN_ERR "getblk(): invalid block size %d requested\n", 10911da177e4SLinus Torvalds size); 1092e1defc4fSMartin K. Petersen printk(KERN_ERR "logical block size: %d\n", 1093e1defc4fSMartin K. Petersen bdev_logical_block_size(bdev)); 10941da177e4SLinus Torvalds 10951da177e4SLinus Torvalds dump_stack(); 10961da177e4SLinus Torvalds return NULL; 10971da177e4SLinus Torvalds } 10981da177e4SLinus Torvalds 10991da177e4SLinus Torvalds for (;;) { 11001da177e4SLinus Torvalds struct buffer_head * bh; 1101e5657933SAndrew Morton int ret; 11021da177e4SLinus Torvalds 11031da177e4SLinus Torvalds bh = __find_get_block(bdev, block, size); 11041da177e4SLinus Torvalds if (bh) 11051da177e4SLinus Torvalds return bh; 11061da177e4SLinus Torvalds 1107e5657933SAndrew Morton ret = grow_buffers(bdev, block, size); 1108e5657933SAndrew Morton if (ret < 0) 1109e5657933SAndrew Morton return NULL; 1110e5657933SAndrew Morton if (ret == 0) 11111da177e4SLinus Torvalds free_more_memory(); 11121da177e4SLinus Torvalds } 11131da177e4SLinus Torvalds } 11141da177e4SLinus Torvalds 11151da177e4SLinus Torvalds /* 11161da177e4SLinus Torvalds * The relationship between dirty buffers and dirty pages: 11171da177e4SLinus Torvalds * 11181da177e4SLinus Torvalds * Whenever a page has any dirty buffers, the page's dirty bit is set, and 11191da177e4SLinus Torvalds * the page is tagged dirty in its radix tree. 11201da177e4SLinus Torvalds * 11211da177e4SLinus Torvalds * At all times, the dirtiness of the buffers represents the dirtiness of 11221da177e4SLinus Torvalds * subsections of the page. If the page has buffers, the page dirty bit is 11231da177e4SLinus Torvalds * merely a hint about the true dirty state. 11241da177e4SLinus Torvalds * 11251da177e4SLinus Torvalds * When a page is set dirty in its entirety, all its buffers are marked dirty 11261da177e4SLinus Torvalds * (if the page has buffers). 11271da177e4SLinus Torvalds * 11281da177e4SLinus Torvalds * When a buffer is marked dirty, its page is dirtied, but the page's other 11291da177e4SLinus Torvalds * buffers are not. 11301da177e4SLinus Torvalds * 11311da177e4SLinus Torvalds * Also. When blockdev buffers are explicitly read with bread(), they 11321da177e4SLinus Torvalds * individually become uptodate. But their backing page remains not 11331da177e4SLinus Torvalds * uptodate - even if all of its buffers are uptodate. A subsequent 11341da177e4SLinus Torvalds * block_read_full_page() against that page will discover all the uptodate 11351da177e4SLinus Torvalds * buffers, will set the page uptodate and will perform no I/O. 11361da177e4SLinus Torvalds */ 11371da177e4SLinus Torvalds 11381da177e4SLinus Torvalds /** 11391da177e4SLinus Torvalds * mark_buffer_dirty - mark a buffer_head as needing writeout 114067be2dd1SMartin Waitz * @bh: the buffer_head to mark dirty 11411da177e4SLinus Torvalds * 11421da177e4SLinus Torvalds * mark_buffer_dirty() will set the dirty bit against the buffer, then set its 11431da177e4SLinus Torvalds * backing page dirty, then tag the page as dirty in its address_space's radix 11441da177e4SLinus Torvalds * tree and then attach the address_space's inode to its superblock's dirty 11451da177e4SLinus Torvalds * inode list. 11461da177e4SLinus Torvalds * 11471da177e4SLinus Torvalds * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, 11481da177e4SLinus Torvalds * mapping->tree_lock and the global inode_lock. 11491da177e4SLinus Torvalds */ 1150fc9b52cdSHarvey Harrison void mark_buffer_dirty(struct buffer_head *bh) 11511da177e4SLinus Torvalds { 1152787d2214SNick Piggin WARN_ON_ONCE(!buffer_uptodate(bh)); 11531be62dc1SLinus Torvalds 11541be62dc1SLinus Torvalds /* 11551be62dc1SLinus Torvalds * Very *carefully* optimize the it-is-already-dirty case. 11561be62dc1SLinus Torvalds * 11571be62dc1SLinus Torvalds * Don't let the final "is it dirty" escape to before we 11581be62dc1SLinus Torvalds * perhaps modified the buffer. 11591be62dc1SLinus Torvalds */ 11601be62dc1SLinus Torvalds if (buffer_dirty(bh)) { 11611be62dc1SLinus Torvalds smp_mb(); 11621be62dc1SLinus Torvalds if (buffer_dirty(bh)) 11631be62dc1SLinus Torvalds return; 11641be62dc1SLinus Torvalds } 11651be62dc1SLinus Torvalds 1166a8e7d49aSLinus Torvalds if (!test_set_buffer_dirty(bh)) { 1167a8e7d49aSLinus Torvalds struct page *page = bh->b_page; 11688e9d78edSLinus Torvalds if (!TestSetPageDirty(page)) { 11698e9d78edSLinus Torvalds struct address_space *mapping = page_mapping(page); 11708e9d78edSLinus Torvalds if (mapping) 11718e9d78edSLinus Torvalds __set_page_dirty(page, mapping, 0); 11728e9d78edSLinus Torvalds } 1173a8e7d49aSLinus Torvalds } 11741da177e4SLinus Torvalds } 11751fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(mark_buffer_dirty); 11761da177e4SLinus Torvalds 11771da177e4SLinus Torvalds /* 11781da177e4SLinus Torvalds * Decrement a buffer_head's reference count. If all buffers against a page 11791da177e4SLinus Torvalds * have zero reference count, are clean and unlocked, and if the page is clean 11801da177e4SLinus Torvalds * and unlocked then try_to_free_buffers() may strip the buffers from the page 11811da177e4SLinus Torvalds * in preparation for freeing it (sometimes, rarely, buffers are removed from 11821da177e4SLinus Torvalds * a page but it ends up not being freed, and buffers may later be reattached). 11831da177e4SLinus Torvalds */ 11841da177e4SLinus Torvalds void __brelse(struct buffer_head * buf) 11851da177e4SLinus Torvalds { 11861da177e4SLinus Torvalds if (atomic_read(&buf->b_count)) { 11871da177e4SLinus Torvalds put_bh(buf); 11881da177e4SLinus Torvalds return; 11891da177e4SLinus Torvalds } 11905c752ad9SArjan van de Ven WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); 11911da177e4SLinus Torvalds } 11921fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(__brelse); 11931da177e4SLinus Torvalds 11941da177e4SLinus Torvalds /* 11951da177e4SLinus Torvalds * bforget() is like brelse(), except it discards any 11961da177e4SLinus Torvalds * potentially dirty data. 11971da177e4SLinus Torvalds */ 11981da177e4SLinus Torvalds void __bforget(struct buffer_head *bh) 11991da177e4SLinus Torvalds { 12001da177e4SLinus Torvalds clear_buffer_dirty(bh); 1201535ee2fbSJan Kara if (bh->b_assoc_map) { 12021da177e4SLinus Torvalds struct address_space *buffer_mapping = bh->b_page->mapping; 12031da177e4SLinus Torvalds 12041da177e4SLinus Torvalds spin_lock(&buffer_mapping->private_lock); 12051da177e4SLinus Torvalds list_del_init(&bh->b_assoc_buffers); 120658ff407bSJan Kara bh->b_assoc_map = NULL; 12071da177e4SLinus Torvalds spin_unlock(&buffer_mapping->private_lock); 12081da177e4SLinus Torvalds } 12091da177e4SLinus Torvalds __brelse(bh); 12101da177e4SLinus Torvalds } 12111fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(__bforget); 12121da177e4SLinus Torvalds 12131da177e4SLinus Torvalds static struct buffer_head *__bread_slow(struct buffer_head *bh) 12141da177e4SLinus Torvalds { 12151da177e4SLinus Torvalds lock_buffer(bh); 12161da177e4SLinus Torvalds if (buffer_uptodate(bh)) { 12171da177e4SLinus Torvalds unlock_buffer(bh); 12181da177e4SLinus Torvalds return bh; 12191da177e4SLinus Torvalds } else { 12201da177e4SLinus Torvalds get_bh(bh); 12211da177e4SLinus Torvalds bh->b_end_io = end_buffer_read_sync; 12221da177e4SLinus Torvalds submit_bh(READ, bh); 12231da177e4SLinus Torvalds wait_on_buffer(bh); 12241da177e4SLinus Torvalds if (buffer_uptodate(bh)) 12251da177e4SLinus Torvalds return bh; 12261da177e4SLinus Torvalds } 12271da177e4SLinus Torvalds brelse(bh); 12281da177e4SLinus Torvalds return NULL; 12291da177e4SLinus Torvalds } 12301da177e4SLinus Torvalds 12311da177e4SLinus Torvalds /* 12321da177e4SLinus Torvalds * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). 12331da177e4SLinus Torvalds * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their 12341da177e4SLinus Torvalds * refcount elevated by one when they're in an LRU. A buffer can only appear 12351da177e4SLinus Torvalds * once in a particular CPU's LRU. A single buffer can be present in multiple 12361da177e4SLinus Torvalds * CPU's LRUs at the same time. 12371da177e4SLinus Torvalds * 12381da177e4SLinus Torvalds * This is a transparent caching front-end to sb_bread(), sb_getblk() and 12391da177e4SLinus Torvalds * sb_find_get_block(). 12401da177e4SLinus Torvalds * 12411da177e4SLinus Torvalds * The LRUs themselves only need locking against invalidate_bh_lrus. We use 12421da177e4SLinus Torvalds * a local interrupt disable for that. 12431da177e4SLinus Torvalds */ 12441da177e4SLinus Torvalds 12451da177e4SLinus Torvalds #define BH_LRU_SIZE 8 12461da177e4SLinus Torvalds 12471da177e4SLinus Torvalds struct bh_lru { 12481da177e4SLinus Torvalds struct buffer_head *bhs[BH_LRU_SIZE]; 12491da177e4SLinus Torvalds }; 12501da177e4SLinus Torvalds 12511da177e4SLinus Torvalds static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; 12521da177e4SLinus Torvalds 12531da177e4SLinus Torvalds #ifdef CONFIG_SMP 12541da177e4SLinus Torvalds #define bh_lru_lock() local_irq_disable() 12551da177e4SLinus Torvalds #define bh_lru_unlock() local_irq_enable() 12561da177e4SLinus Torvalds #else 12571da177e4SLinus Torvalds #define bh_lru_lock() preempt_disable() 12581da177e4SLinus Torvalds #define bh_lru_unlock() preempt_enable() 12591da177e4SLinus Torvalds #endif 12601da177e4SLinus Torvalds 12611da177e4SLinus Torvalds static inline void check_irqs_on(void) 12621da177e4SLinus Torvalds { 12631da177e4SLinus Torvalds #ifdef irqs_disabled 12641da177e4SLinus Torvalds BUG_ON(irqs_disabled()); 12651da177e4SLinus Torvalds #endif 12661da177e4SLinus Torvalds } 12671da177e4SLinus Torvalds 12681da177e4SLinus Torvalds /* 12691da177e4SLinus Torvalds * The LRU management algorithm is dopey-but-simple. Sorry. 12701da177e4SLinus Torvalds */ 12711da177e4SLinus Torvalds static void bh_lru_install(struct buffer_head *bh) 12721da177e4SLinus Torvalds { 12731da177e4SLinus Torvalds struct buffer_head *evictee = NULL; 12741da177e4SLinus Torvalds struct bh_lru *lru; 12751da177e4SLinus Torvalds 12761da177e4SLinus Torvalds check_irqs_on(); 12771da177e4SLinus Torvalds bh_lru_lock(); 12781da177e4SLinus Torvalds lru = &__get_cpu_var(bh_lrus); 12791da177e4SLinus Torvalds if (lru->bhs[0] != bh) { 12801da177e4SLinus Torvalds struct buffer_head *bhs[BH_LRU_SIZE]; 12811da177e4SLinus Torvalds int in; 12821da177e4SLinus Torvalds int out = 0; 12831da177e4SLinus Torvalds 12841da177e4SLinus Torvalds get_bh(bh); 12851da177e4SLinus Torvalds bhs[out++] = bh; 12861da177e4SLinus Torvalds for (in = 0; in < BH_LRU_SIZE; in++) { 12871da177e4SLinus Torvalds struct buffer_head *bh2 = lru->bhs[in]; 12881da177e4SLinus Torvalds 12891da177e4SLinus Torvalds if (bh2 == bh) { 12901da177e4SLinus Torvalds __brelse(bh2); 12911da177e4SLinus Torvalds } else { 12921da177e4SLinus Torvalds if (out >= BH_LRU_SIZE) { 12931da177e4SLinus Torvalds BUG_ON(evictee != NULL); 12941da177e4SLinus Torvalds evictee = bh2; 12951da177e4SLinus Torvalds } else { 12961da177e4SLinus Torvalds bhs[out++] = bh2; 12971da177e4SLinus Torvalds } 12981da177e4SLinus Torvalds } 12991da177e4SLinus Torvalds } 13001da177e4SLinus Torvalds while (out < BH_LRU_SIZE) 13011da177e4SLinus Torvalds bhs[out++] = NULL; 13021da177e4SLinus Torvalds memcpy(lru->bhs, bhs, sizeof(bhs)); 13031da177e4SLinus Torvalds } 13041da177e4SLinus Torvalds bh_lru_unlock(); 13051da177e4SLinus Torvalds 13061da177e4SLinus Torvalds if (evictee) 13071da177e4SLinus Torvalds __brelse(evictee); 13081da177e4SLinus Torvalds } 13091da177e4SLinus Torvalds 13101da177e4SLinus Torvalds /* 13111da177e4SLinus Torvalds * Look up the bh in this cpu's LRU. If it's there, move it to the head. 13121da177e4SLinus Torvalds */ 1313858119e1SArjan van de Ven static struct buffer_head * 13143991d3bdSTomasz Kvarsin lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) 13151da177e4SLinus Torvalds { 13161da177e4SLinus Torvalds struct buffer_head *ret = NULL; 13171da177e4SLinus Torvalds struct bh_lru *lru; 13183991d3bdSTomasz Kvarsin unsigned int i; 13191da177e4SLinus Torvalds 13201da177e4SLinus Torvalds check_irqs_on(); 13211da177e4SLinus Torvalds bh_lru_lock(); 13221da177e4SLinus Torvalds lru = &__get_cpu_var(bh_lrus); 13231da177e4SLinus Torvalds for (i = 0; i < BH_LRU_SIZE; i++) { 13241da177e4SLinus Torvalds struct buffer_head *bh = lru->bhs[i]; 13251da177e4SLinus Torvalds 13261da177e4SLinus Torvalds if (bh && bh->b_bdev == bdev && 13271da177e4SLinus Torvalds bh->b_blocknr == block && bh->b_size == size) { 13281da177e4SLinus Torvalds if (i) { 13291da177e4SLinus Torvalds while (i) { 13301da177e4SLinus Torvalds lru->bhs[i] = lru->bhs[i - 1]; 13311da177e4SLinus Torvalds i--; 13321da177e4SLinus Torvalds } 13331da177e4SLinus Torvalds lru->bhs[0] = bh; 13341da177e4SLinus Torvalds } 13351da177e4SLinus Torvalds get_bh(bh); 13361da177e4SLinus Torvalds ret = bh; 13371da177e4SLinus Torvalds break; 13381da177e4SLinus Torvalds } 13391da177e4SLinus Torvalds } 13401da177e4SLinus Torvalds bh_lru_unlock(); 13411da177e4SLinus Torvalds return ret; 13421da177e4SLinus Torvalds } 13431da177e4SLinus Torvalds 13441da177e4SLinus Torvalds /* 13451da177e4SLinus Torvalds * Perform a pagecache lookup for the matching buffer. If it's there, refresh 13461da177e4SLinus Torvalds * it in the LRU and mark it as accessed. If it is not present then return 13471da177e4SLinus Torvalds * NULL 13481da177e4SLinus Torvalds */ 13491da177e4SLinus Torvalds struct buffer_head * 13503991d3bdSTomasz Kvarsin __find_get_block(struct block_device *bdev, sector_t block, unsigned size) 13511da177e4SLinus Torvalds { 13521da177e4SLinus Torvalds struct buffer_head *bh = lookup_bh_lru(bdev, block, size); 13531da177e4SLinus Torvalds 13541da177e4SLinus Torvalds if (bh == NULL) { 1355385fd4c5SCoywolf Qi Hunt bh = __find_get_block_slow(bdev, block); 13561da177e4SLinus Torvalds if (bh) 13571da177e4SLinus Torvalds bh_lru_install(bh); 13581da177e4SLinus Torvalds } 13591da177e4SLinus Torvalds if (bh) 13601da177e4SLinus Torvalds touch_buffer(bh); 13611da177e4SLinus Torvalds return bh; 13621da177e4SLinus Torvalds } 13631da177e4SLinus Torvalds EXPORT_SYMBOL(__find_get_block); 13641da177e4SLinus Torvalds 13651da177e4SLinus Torvalds /* 13661da177e4SLinus Torvalds * __getblk will locate (and, if necessary, create) the buffer_head 13671da177e4SLinus Torvalds * which corresponds to the passed block_device, block and size. The 13681da177e4SLinus Torvalds * returned buffer has its reference count incremented. 13691da177e4SLinus Torvalds * 13701da177e4SLinus Torvalds * __getblk() cannot fail - it just keeps trying. If you pass it an 13711da177e4SLinus Torvalds * illegal block number, __getblk() will happily return a buffer_head 13721da177e4SLinus Torvalds * which represents the non-existent block. Very weird. 13731da177e4SLinus Torvalds * 13741da177e4SLinus Torvalds * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() 13751da177e4SLinus Torvalds * attempt is failing. FIXME, perhaps? 13761da177e4SLinus Torvalds */ 13771da177e4SLinus Torvalds struct buffer_head * 13783991d3bdSTomasz Kvarsin __getblk(struct block_device *bdev, sector_t block, unsigned size) 13791da177e4SLinus Torvalds { 13801da177e4SLinus Torvalds struct buffer_head *bh = __find_get_block(bdev, block, size); 13811da177e4SLinus Torvalds 13821da177e4SLinus Torvalds might_sleep(); 13831da177e4SLinus Torvalds if (bh == NULL) 13841da177e4SLinus Torvalds bh = __getblk_slow(bdev, block, size); 13851da177e4SLinus Torvalds return bh; 13861da177e4SLinus Torvalds } 13871da177e4SLinus Torvalds EXPORT_SYMBOL(__getblk); 13881da177e4SLinus Torvalds 13891da177e4SLinus Torvalds /* 13901da177e4SLinus Torvalds * Do async read-ahead on a buffer.. 13911da177e4SLinus Torvalds */ 13923991d3bdSTomasz Kvarsin void __breadahead(struct block_device *bdev, sector_t block, unsigned size) 13931da177e4SLinus Torvalds { 13941da177e4SLinus Torvalds struct buffer_head *bh = __getblk(bdev, block, size); 1395a3e713b5SAndrew Morton if (likely(bh)) { 13961da177e4SLinus Torvalds ll_rw_block(READA, 1, &bh); 13971da177e4SLinus Torvalds brelse(bh); 13981da177e4SLinus Torvalds } 1399a3e713b5SAndrew Morton } 14001da177e4SLinus Torvalds EXPORT_SYMBOL(__breadahead); 14011da177e4SLinus Torvalds 14021da177e4SLinus Torvalds /** 14031da177e4SLinus Torvalds * __bread() - reads a specified block and returns the bh 140467be2dd1SMartin Waitz * @bdev: the block_device to read from 14051da177e4SLinus Torvalds * @block: number of block 14061da177e4SLinus Torvalds * @size: size (in bytes) to read 14071da177e4SLinus Torvalds * 14081da177e4SLinus Torvalds * Reads a specified block, and returns buffer head that contains it. 14091da177e4SLinus Torvalds * It returns NULL if the block was unreadable. 14101da177e4SLinus Torvalds */ 14111da177e4SLinus Torvalds struct buffer_head * 14123991d3bdSTomasz Kvarsin __bread(struct block_device *bdev, sector_t block, unsigned size) 14131da177e4SLinus Torvalds { 14141da177e4SLinus Torvalds struct buffer_head *bh = __getblk(bdev, block, size); 14151da177e4SLinus Torvalds 1416a3e713b5SAndrew Morton if (likely(bh) && !buffer_uptodate(bh)) 14171da177e4SLinus Torvalds bh = __bread_slow(bh); 14181da177e4SLinus Torvalds return bh; 14191da177e4SLinus Torvalds } 14201da177e4SLinus Torvalds EXPORT_SYMBOL(__bread); 14211da177e4SLinus Torvalds 14221da177e4SLinus Torvalds /* 14231da177e4SLinus Torvalds * invalidate_bh_lrus() is called rarely - but not only at unmount. 14241da177e4SLinus Torvalds * This doesn't race because it runs in each cpu either in irq 14251da177e4SLinus Torvalds * or with preempt disabled. 14261da177e4SLinus Torvalds */ 14271da177e4SLinus Torvalds static void invalidate_bh_lru(void *arg) 14281da177e4SLinus Torvalds { 14291da177e4SLinus Torvalds struct bh_lru *b = &get_cpu_var(bh_lrus); 14301da177e4SLinus Torvalds int i; 14311da177e4SLinus Torvalds 14321da177e4SLinus Torvalds for (i = 0; i < BH_LRU_SIZE; i++) { 14331da177e4SLinus Torvalds brelse(b->bhs[i]); 14341da177e4SLinus Torvalds b->bhs[i] = NULL; 14351da177e4SLinus Torvalds } 14361da177e4SLinus Torvalds put_cpu_var(bh_lrus); 14371da177e4SLinus Torvalds } 14381da177e4SLinus Torvalds 1439f9a14399SPeter Zijlstra void invalidate_bh_lrus(void) 14401da177e4SLinus Torvalds { 144115c8b6c1SJens Axboe on_each_cpu(invalidate_bh_lru, NULL, 1); 14421da177e4SLinus Torvalds } 14439db5579bSNick Piggin EXPORT_SYMBOL_GPL(invalidate_bh_lrus); 14441da177e4SLinus Torvalds 14451da177e4SLinus Torvalds void set_bh_page(struct buffer_head *bh, 14461da177e4SLinus Torvalds struct page *page, unsigned long offset) 14471da177e4SLinus Torvalds { 14481da177e4SLinus Torvalds bh->b_page = page; 1449e827f923SEric Sesterhenn BUG_ON(offset >= PAGE_SIZE); 14501da177e4SLinus Torvalds if (PageHighMem(page)) 14511da177e4SLinus Torvalds /* 14521da177e4SLinus Torvalds * This catches illegal uses and preserves the offset: 14531da177e4SLinus Torvalds */ 14541da177e4SLinus Torvalds bh->b_data = (char *)(0 + offset); 14551da177e4SLinus Torvalds else 14561da177e4SLinus Torvalds bh->b_data = page_address(page) + offset; 14571da177e4SLinus Torvalds } 14581da177e4SLinus Torvalds EXPORT_SYMBOL(set_bh_page); 14591da177e4SLinus Torvalds 14601da177e4SLinus Torvalds /* 14611da177e4SLinus Torvalds * Called when truncating a buffer on a page completely. 14621da177e4SLinus Torvalds */ 1463858119e1SArjan van de Ven static void discard_buffer(struct buffer_head * bh) 14641da177e4SLinus Torvalds { 14651da177e4SLinus Torvalds lock_buffer(bh); 14661da177e4SLinus Torvalds clear_buffer_dirty(bh); 14671da177e4SLinus Torvalds bh->b_bdev = NULL; 14681da177e4SLinus Torvalds clear_buffer_mapped(bh); 14691da177e4SLinus Torvalds clear_buffer_req(bh); 14701da177e4SLinus Torvalds clear_buffer_new(bh); 14711da177e4SLinus Torvalds clear_buffer_delay(bh); 147233a266ddSDavid Chinner clear_buffer_unwritten(bh); 14731da177e4SLinus Torvalds unlock_buffer(bh); 14741da177e4SLinus Torvalds } 14751da177e4SLinus Torvalds 14761da177e4SLinus Torvalds /** 14771da177e4SLinus Torvalds * block_invalidatepage - invalidate part of all of a buffer-backed page 14781da177e4SLinus Torvalds * 14791da177e4SLinus Torvalds * @page: the page which is affected 14801da177e4SLinus Torvalds * @offset: the index of the truncation point 14811da177e4SLinus Torvalds * 14821da177e4SLinus Torvalds * block_invalidatepage() is called when all or part of the page has become 14831da177e4SLinus Torvalds * invalidatedby a truncate operation. 14841da177e4SLinus Torvalds * 14851da177e4SLinus Torvalds * block_invalidatepage() does not have to release all buffers, but it must 14861da177e4SLinus Torvalds * ensure that no dirty buffer is left outside @offset and that no I/O 14871da177e4SLinus Torvalds * is underway against any of the blocks which are outside the truncation 14881da177e4SLinus Torvalds * point. Because the caller is about to free (and possibly reuse) those 14891da177e4SLinus Torvalds * blocks on-disk. 14901da177e4SLinus Torvalds */ 14912ff28e22SNeilBrown void block_invalidatepage(struct page *page, unsigned long offset) 14921da177e4SLinus Torvalds { 14931da177e4SLinus Torvalds struct buffer_head *head, *bh, *next; 14941da177e4SLinus Torvalds unsigned int curr_off = 0; 14951da177e4SLinus Torvalds 14961da177e4SLinus Torvalds BUG_ON(!PageLocked(page)); 14971da177e4SLinus Torvalds if (!page_has_buffers(page)) 14981da177e4SLinus Torvalds goto out; 14991da177e4SLinus Torvalds 15001da177e4SLinus Torvalds head = page_buffers(page); 15011da177e4SLinus Torvalds bh = head; 15021da177e4SLinus Torvalds do { 15031da177e4SLinus Torvalds unsigned int next_off = curr_off + bh->b_size; 15041da177e4SLinus Torvalds next = bh->b_this_page; 15051da177e4SLinus Torvalds 15061da177e4SLinus Torvalds /* 15071da177e4SLinus Torvalds * is this block fully invalidated? 15081da177e4SLinus Torvalds */ 15091da177e4SLinus Torvalds if (offset <= curr_off) 15101da177e4SLinus Torvalds discard_buffer(bh); 15111da177e4SLinus Torvalds curr_off = next_off; 15121da177e4SLinus Torvalds bh = next; 15131da177e4SLinus Torvalds } while (bh != head); 15141da177e4SLinus Torvalds 15151da177e4SLinus Torvalds /* 15161da177e4SLinus Torvalds * We release buffers only if the entire page is being invalidated. 15171da177e4SLinus Torvalds * The get_block cached value has been unconditionally invalidated, 15181da177e4SLinus Torvalds * so real IO is not possible anymore. 15191da177e4SLinus Torvalds */ 15201da177e4SLinus Torvalds if (offset == 0) 15212ff28e22SNeilBrown try_to_release_page(page, 0); 15221da177e4SLinus Torvalds out: 15232ff28e22SNeilBrown return; 15241da177e4SLinus Torvalds } 15251da177e4SLinus Torvalds EXPORT_SYMBOL(block_invalidatepage); 15261da177e4SLinus Torvalds 15271da177e4SLinus Torvalds /* 15281da177e4SLinus Torvalds * We attach and possibly dirty the buffers atomically wrt 15291da177e4SLinus Torvalds * __set_page_dirty_buffers() via private_lock. try_to_free_buffers 15301da177e4SLinus Torvalds * is already excluded via the page lock. 15311da177e4SLinus Torvalds */ 15321da177e4SLinus Torvalds void create_empty_buffers(struct page *page, 15331da177e4SLinus Torvalds unsigned long blocksize, unsigned long b_state) 15341da177e4SLinus Torvalds { 15351da177e4SLinus Torvalds struct buffer_head *bh, *head, *tail; 15361da177e4SLinus Torvalds 15371da177e4SLinus Torvalds head = alloc_page_buffers(page, blocksize, 1); 15381da177e4SLinus Torvalds bh = head; 15391da177e4SLinus Torvalds do { 15401da177e4SLinus Torvalds bh->b_state |= b_state; 15411da177e4SLinus Torvalds tail = bh; 15421da177e4SLinus Torvalds bh = bh->b_this_page; 15431da177e4SLinus Torvalds } while (bh); 15441da177e4SLinus Torvalds tail->b_this_page = head; 15451da177e4SLinus Torvalds 15461da177e4SLinus Torvalds spin_lock(&page->mapping->private_lock); 15471da177e4SLinus Torvalds if (PageUptodate(page) || PageDirty(page)) { 15481da177e4SLinus Torvalds bh = head; 15491da177e4SLinus Torvalds do { 15501da177e4SLinus Torvalds if (PageDirty(page)) 15511da177e4SLinus Torvalds set_buffer_dirty(bh); 15521da177e4SLinus Torvalds if (PageUptodate(page)) 15531da177e4SLinus Torvalds set_buffer_uptodate(bh); 15541da177e4SLinus Torvalds bh = bh->b_this_page; 15551da177e4SLinus Torvalds } while (bh != head); 15561da177e4SLinus Torvalds } 15571da177e4SLinus Torvalds attach_page_buffers(page, head); 15581da177e4SLinus Torvalds spin_unlock(&page->mapping->private_lock); 15591da177e4SLinus Torvalds } 15601da177e4SLinus Torvalds EXPORT_SYMBOL(create_empty_buffers); 15611da177e4SLinus Torvalds 15621da177e4SLinus Torvalds /* 15631da177e4SLinus Torvalds * We are taking a block for data and we don't want any output from any 15641da177e4SLinus Torvalds * buffer-cache aliases starting from return from that function and 15651da177e4SLinus Torvalds * until the moment when something will explicitly mark the buffer 15661da177e4SLinus Torvalds * dirty (hopefully that will not happen until we will free that block ;-) 15671da177e4SLinus Torvalds * We don't even need to mark it not-uptodate - nobody can expect 15681da177e4SLinus Torvalds * anything from a newly allocated buffer anyway. We used to used 15691da177e4SLinus Torvalds * unmap_buffer() for such invalidation, but that was wrong. We definitely 15701da177e4SLinus Torvalds * don't want to mark the alias unmapped, for example - it would confuse 15711da177e4SLinus Torvalds * anyone who might pick it with bread() afterwards... 15721da177e4SLinus Torvalds * 15731da177e4SLinus Torvalds * Also.. Note that bforget() doesn't lock the buffer. So there can 15741da177e4SLinus Torvalds * be writeout I/O going on against recently-freed buffers. We don't 15751da177e4SLinus Torvalds * wait on that I/O in bforget() - it's more efficient to wait on the I/O 15761da177e4SLinus Torvalds * only if we really need to. That happens here. 15771da177e4SLinus Torvalds */ 15781da177e4SLinus Torvalds void unmap_underlying_metadata(struct block_device *bdev, sector_t block) 15791da177e4SLinus Torvalds { 15801da177e4SLinus Torvalds struct buffer_head *old_bh; 15811da177e4SLinus Torvalds 15821da177e4SLinus Torvalds might_sleep(); 15831da177e4SLinus Torvalds 1584385fd4c5SCoywolf Qi Hunt old_bh = __find_get_block_slow(bdev, block); 15851da177e4SLinus Torvalds if (old_bh) { 15861da177e4SLinus Torvalds clear_buffer_dirty(old_bh); 15871da177e4SLinus Torvalds wait_on_buffer(old_bh); 15881da177e4SLinus Torvalds clear_buffer_req(old_bh); 15891da177e4SLinus Torvalds __brelse(old_bh); 15901da177e4SLinus Torvalds } 15911da177e4SLinus Torvalds } 15921da177e4SLinus Torvalds EXPORT_SYMBOL(unmap_underlying_metadata); 15931da177e4SLinus Torvalds 15941da177e4SLinus Torvalds /* 15951da177e4SLinus Torvalds * NOTE! All mapped/uptodate combinations are valid: 15961da177e4SLinus Torvalds * 15971da177e4SLinus Torvalds * Mapped Uptodate Meaning 15981da177e4SLinus Torvalds * 15991da177e4SLinus Torvalds * No No "unknown" - must do get_block() 16001da177e4SLinus Torvalds * No Yes "hole" - zero-filled 16011da177e4SLinus Torvalds * Yes No "allocated" - allocated on disk, not read in 16021da177e4SLinus Torvalds * Yes Yes "valid" - allocated and up-to-date in memory. 16031da177e4SLinus Torvalds * 16041da177e4SLinus Torvalds * "Dirty" is valid only with the last case (mapped+uptodate). 16051da177e4SLinus Torvalds */ 16061da177e4SLinus Torvalds 16071da177e4SLinus Torvalds /* 16081da177e4SLinus Torvalds * While block_write_full_page is writing back the dirty buffers under 16091da177e4SLinus Torvalds * the page lock, whoever dirtied the buffers may decide to clean them 16101da177e4SLinus Torvalds * again at any time. We handle that by only looking at the buffer 16111da177e4SLinus Torvalds * state inside lock_buffer(). 16121da177e4SLinus Torvalds * 16131da177e4SLinus Torvalds * If block_write_full_page() is called for regular writeback 16141da177e4SLinus Torvalds * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a 16151da177e4SLinus Torvalds * locked buffer. This only can happen if someone has written the buffer 16161da177e4SLinus Torvalds * directly, with submit_bh(). At the address_space level PageWriteback 16171da177e4SLinus Torvalds * prevents this contention from occurring. 16186e34eeddSTheodore Ts'o * 16196e34eeddSTheodore Ts'o * If block_write_full_page() is called with wbc->sync_mode == 16206e34eeddSTheodore Ts'o * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this 16216e34eeddSTheodore Ts'o * causes the writes to be flagged as synchronous writes, but the 16226e34eeddSTheodore Ts'o * block device queue will NOT be unplugged, since usually many pages 16236e34eeddSTheodore Ts'o * will be pushed to the out before the higher-level caller actually 16246e34eeddSTheodore Ts'o * waits for the writes to be completed. The various wait functions, 16256e34eeddSTheodore Ts'o * such as wait_on_writeback_range() will ultimately call sync_page() 16266e34eeddSTheodore Ts'o * which will ultimately call blk_run_backing_dev(), which will end up 16276e34eeddSTheodore Ts'o * unplugging the device queue. 16281da177e4SLinus Torvalds */ 16291da177e4SLinus Torvalds static int __block_write_full_page(struct inode *inode, struct page *page, 163035c80d5fSChris Mason get_block_t *get_block, struct writeback_control *wbc, 163135c80d5fSChris Mason bh_end_io_t *handler) 16321da177e4SLinus Torvalds { 16331da177e4SLinus Torvalds int err; 16341da177e4SLinus Torvalds sector_t block; 16351da177e4SLinus Torvalds sector_t last_block; 1636f0fbd5fcSAndrew Morton struct buffer_head *bh, *head; 1637b0cf2321SBadari Pulavarty const unsigned blocksize = 1 << inode->i_blkbits; 16381da177e4SLinus Torvalds int nr_underway = 0; 16396e34eeddSTheodore Ts'o int write_op = (wbc->sync_mode == WB_SYNC_ALL ? 16406e34eeddSTheodore Ts'o WRITE_SYNC_PLUG : WRITE); 16411da177e4SLinus Torvalds 16421da177e4SLinus Torvalds BUG_ON(!PageLocked(page)); 16431da177e4SLinus Torvalds 16441da177e4SLinus Torvalds last_block = (i_size_read(inode) - 1) >> inode->i_blkbits; 16451da177e4SLinus Torvalds 16461da177e4SLinus Torvalds if (!page_has_buffers(page)) { 1647b0cf2321SBadari Pulavarty create_empty_buffers(page, blocksize, 16481da177e4SLinus Torvalds (1 << BH_Dirty)|(1 << BH_Uptodate)); 16491da177e4SLinus Torvalds } 16501da177e4SLinus Torvalds 16511da177e4SLinus Torvalds /* 16521da177e4SLinus Torvalds * Be very careful. We have no exclusion from __set_page_dirty_buffers 16531da177e4SLinus Torvalds * here, and the (potentially unmapped) buffers may become dirty at 16541da177e4SLinus Torvalds * any time. If a buffer becomes dirty here after we've inspected it 16551da177e4SLinus Torvalds * then we just miss that fact, and the page stays dirty. 16561da177e4SLinus Torvalds * 16571da177e4SLinus Torvalds * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; 16581da177e4SLinus Torvalds * handle that here by just cleaning them. 16591da177e4SLinus Torvalds */ 16601da177e4SLinus Torvalds 166154b21a79SAndrew Morton block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 16621da177e4SLinus Torvalds head = page_buffers(page); 16631da177e4SLinus Torvalds bh = head; 16641da177e4SLinus Torvalds 16651da177e4SLinus Torvalds /* 16661da177e4SLinus Torvalds * Get all the dirty buffers mapped to disk addresses and 16671da177e4SLinus Torvalds * handle any aliases from the underlying blockdev's mapping. 16681da177e4SLinus Torvalds */ 16691da177e4SLinus Torvalds do { 16701da177e4SLinus Torvalds if (block > last_block) { 16711da177e4SLinus Torvalds /* 16721da177e4SLinus Torvalds * mapped buffers outside i_size will occur, because 16731da177e4SLinus Torvalds * this page can be outside i_size when there is a 16741da177e4SLinus Torvalds * truncate in progress. 16751da177e4SLinus Torvalds */ 16761da177e4SLinus Torvalds /* 16771da177e4SLinus Torvalds * The buffer was zeroed by block_write_full_page() 16781da177e4SLinus Torvalds */ 16791da177e4SLinus Torvalds clear_buffer_dirty(bh); 16801da177e4SLinus Torvalds set_buffer_uptodate(bh); 168129a814d2SAlex Tomas } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && 168229a814d2SAlex Tomas buffer_dirty(bh)) { 1683b0cf2321SBadari Pulavarty WARN_ON(bh->b_size != blocksize); 16841da177e4SLinus Torvalds err = get_block(inode, block, bh, 1); 16851da177e4SLinus Torvalds if (err) 16861da177e4SLinus Torvalds goto recover; 168729a814d2SAlex Tomas clear_buffer_delay(bh); 16881da177e4SLinus Torvalds if (buffer_new(bh)) { 16891da177e4SLinus Torvalds /* blockdev mappings never come here */ 16901da177e4SLinus Torvalds clear_buffer_new(bh); 16911da177e4SLinus Torvalds unmap_underlying_metadata(bh->b_bdev, 16921da177e4SLinus Torvalds bh->b_blocknr); 16931da177e4SLinus Torvalds } 16941da177e4SLinus Torvalds } 16951da177e4SLinus Torvalds bh = bh->b_this_page; 16961da177e4SLinus Torvalds block++; 16971da177e4SLinus Torvalds } while (bh != head); 16981da177e4SLinus Torvalds 16991da177e4SLinus Torvalds do { 17001da177e4SLinus Torvalds if (!buffer_mapped(bh)) 17011da177e4SLinus Torvalds continue; 17021da177e4SLinus Torvalds /* 17031da177e4SLinus Torvalds * If it's a fully non-blocking write attempt and we cannot 17041da177e4SLinus Torvalds * lock the buffer then redirty the page. Note that this can 17055b0830cbSJens Axboe * potentially cause a busy-wait loop from writeback threads 17065b0830cbSJens Axboe * and kswapd activity, but those code paths have their own 17075b0830cbSJens Axboe * higher-level throttling. 17081da177e4SLinus Torvalds */ 17091da177e4SLinus Torvalds if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) { 17101da177e4SLinus Torvalds lock_buffer(bh); 1711ca5de404SNick Piggin } else if (!trylock_buffer(bh)) { 17121da177e4SLinus Torvalds redirty_page_for_writepage(wbc, page); 17131da177e4SLinus Torvalds continue; 17141da177e4SLinus Torvalds } 17151da177e4SLinus Torvalds if (test_clear_buffer_dirty(bh)) { 171635c80d5fSChris Mason mark_buffer_async_write_endio(bh, handler); 17171da177e4SLinus Torvalds } else { 17181da177e4SLinus Torvalds unlock_buffer(bh); 17191da177e4SLinus Torvalds } 17201da177e4SLinus Torvalds } while ((bh = bh->b_this_page) != head); 17211da177e4SLinus Torvalds 17221da177e4SLinus Torvalds /* 17231da177e4SLinus Torvalds * The page and its buffers are protected by PageWriteback(), so we can 17241da177e4SLinus Torvalds * drop the bh refcounts early. 17251da177e4SLinus Torvalds */ 17261da177e4SLinus Torvalds BUG_ON(PageWriteback(page)); 17271da177e4SLinus Torvalds set_page_writeback(page); 17281da177e4SLinus Torvalds 17291da177e4SLinus Torvalds do { 17301da177e4SLinus Torvalds struct buffer_head *next = bh->b_this_page; 17311da177e4SLinus Torvalds if (buffer_async_write(bh)) { 1732a64c8610STheodore Ts'o submit_bh(write_op, bh); 17331da177e4SLinus Torvalds nr_underway++; 1734ad576e63SNick Piggin } 17351da177e4SLinus Torvalds bh = next; 17361da177e4SLinus Torvalds } while (bh != head); 173705937baaSAndrew Morton unlock_page(page); 17381da177e4SLinus Torvalds 17391da177e4SLinus Torvalds err = 0; 17401da177e4SLinus Torvalds done: 17411da177e4SLinus Torvalds if (nr_underway == 0) { 17421da177e4SLinus Torvalds /* 17431da177e4SLinus Torvalds * The page was marked dirty, but the buffers were 17441da177e4SLinus Torvalds * clean. Someone wrote them back by hand with 17451da177e4SLinus Torvalds * ll_rw_block/submit_bh. A rare case. 17461da177e4SLinus Torvalds */ 17471da177e4SLinus Torvalds end_page_writeback(page); 17483d67f2d7SNick Piggin 17491da177e4SLinus Torvalds /* 17501da177e4SLinus Torvalds * The page and buffer_heads can be released at any time from 17511da177e4SLinus Torvalds * here on. 17521da177e4SLinus Torvalds */ 17531da177e4SLinus Torvalds } 17541da177e4SLinus Torvalds return err; 17551da177e4SLinus Torvalds 17561da177e4SLinus Torvalds recover: 17571da177e4SLinus Torvalds /* 17581da177e4SLinus Torvalds * ENOSPC, or some other error. We may already have added some 17591da177e4SLinus Torvalds * blocks to the file, so we need to write these out to avoid 17601da177e4SLinus Torvalds * exposing stale data. 17611da177e4SLinus Torvalds * The page is currently locked and not marked for writeback 17621da177e4SLinus Torvalds */ 17631da177e4SLinus Torvalds bh = head; 17641da177e4SLinus Torvalds /* Recovery: lock and submit the mapped buffers */ 17651da177e4SLinus Torvalds do { 176629a814d2SAlex Tomas if (buffer_mapped(bh) && buffer_dirty(bh) && 176729a814d2SAlex Tomas !buffer_delay(bh)) { 17681da177e4SLinus Torvalds lock_buffer(bh); 176935c80d5fSChris Mason mark_buffer_async_write_endio(bh, handler); 17701da177e4SLinus Torvalds } else { 17711da177e4SLinus Torvalds /* 17721da177e4SLinus Torvalds * The buffer may have been set dirty during 17731da177e4SLinus Torvalds * attachment to a dirty page. 17741da177e4SLinus Torvalds */ 17751da177e4SLinus Torvalds clear_buffer_dirty(bh); 17761da177e4SLinus Torvalds } 17771da177e4SLinus Torvalds } while ((bh = bh->b_this_page) != head); 17781da177e4SLinus Torvalds SetPageError(page); 17791da177e4SLinus Torvalds BUG_ON(PageWriteback(page)); 17807e4c3690SAndrew Morton mapping_set_error(page->mapping, err); 17811da177e4SLinus Torvalds set_page_writeback(page); 17821da177e4SLinus Torvalds do { 17831da177e4SLinus Torvalds struct buffer_head *next = bh->b_this_page; 17841da177e4SLinus Torvalds if (buffer_async_write(bh)) { 17851da177e4SLinus Torvalds clear_buffer_dirty(bh); 1786a64c8610STheodore Ts'o submit_bh(write_op, bh); 17871da177e4SLinus Torvalds nr_underway++; 1788ad576e63SNick Piggin } 17891da177e4SLinus Torvalds bh = next; 17901da177e4SLinus Torvalds } while (bh != head); 1791ffda9d30SNick Piggin unlock_page(page); 17921da177e4SLinus Torvalds goto done; 17931da177e4SLinus Torvalds } 17941da177e4SLinus Torvalds 1795afddba49SNick Piggin /* 1796afddba49SNick Piggin * If a page has any new buffers, zero them out here, and mark them uptodate 1797afddba49SNick Piggin * and dirty so they'll be written out (in order to prevent uninitialised 1798afddba49SNick Piggin * block data from leaking). And clear the new bit. 1799afddba49SNick Piggin */ 1800afddba49SNick Piggin void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) 1801afddba49SNick Piggin { 1802afddba49SNick Piggin unsigned int block_start, block_end; 1803afddba49SNick Piggin struct buffer_head *head, *bh; 1804afddba49SNick Piggin 1805afddba49SNick Piggin BUG_ON(!PageLocked(page)); 1806afddba49SNick Piggin if (!page_has_buffers(page)) 1807afddba49SNick Piggin return; 1808afddba49SNick Piggin 1809afddba49SNick Piggin bh = head = page_buffers(page); 1810afddba49SNick Piggin block_start = 0; 1811afddba49SNick Piggin do { 1812afddba49SNick Piggin block_end = block_start + bh->b_size; 1813afddba49SNick Piggin 1814afddba49SNick Piggin if (buffer_new(bh)) { 1815afddba49SNick Piggin if (block_end > from && block_start < to) { 1816afddba49SNick Piggin if (!PageUptodate(page)) { 1817afddba49SNick Piggin unsigned start, size; 1818afddba49SNick Piggin 1819afddba49SNick Piggin start = max(from, block_start); 1820afddba49SNick Piggin size = min(to, block_end) - start; 1821afddba49SNick Piggin 1822eebd2aa3SChristoph Lameter zero_user(page, start, size); 1823afddba49SNick Piggin set_buffer_uptodate(bh); 1824afddba49SNick Piggin } 1825afddba49SNick Piggin 1826afddba49SNick Piggin clear_buffer_new(bh); 1827afddba49SNick Piggin mark_buffer_dirty(bh); 1828afddba49SNick Piggin } 1829afddba49SNick Piggin } 1830afddba49SNick Piggin 1831afddba49SNick Piggin block_start = block_end; 1832afddba49SNick Piggin bh = bh->b_this_page; 1833afddba49SNick Piggin } while (bh != head); 1834afddba49SNick Piggin } 1835afddba49SNick Piggin EXPORT_SYMBOL(page_zero_new_buffers); 1836afddba49SNick Piggin 18376e1db88dSChristoph Hellwig int block_prepare_write(struct page *page, unsigned from, unsigned to, 18386e1db88dSChristoph Hellwig get_block_t *get_block) 18391da177e4SLinus Torvalds { 18406e1db88dSChristoph Hellwig struct inode *inode = page->mapping->host; 18411da177e4SLinus Torvalds unsigned block_start, block_end; 18421da177e4SLinus Torvalds sector_t block; 18431da177e4SLinus Torvalds int err = 0; 18441da177e4SLinus Torvalds unsigned blocksize, bbits; 18451da177e4SLinus Torvalds struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; 18461da177e4SLinus Torvalds 18471da177e4SLinus Torvalds BUG_ON(!PageLocked(page)); 18481da177e4SLinus Torvalds BUG_ON(from > PAGE_CACHE_SIZE); 18491da177e4SLinus Torvalds BUG_ON(to > PAGE_CACHE_SIZE); 18501da177e4SLinus Torvalds BUG_ON(from > to); 18511da177e4SLinus Torvalds 18521da177e4SLinus Torvalds blocksize = 1 << inode->i_blkbits; 18531da177e4SLinus Torvalds if (!page_has_buffers(page)) 18541da177e4SLinus Torvalds create_empty_buffers(page, blocksize, 0); 18551da177e4SLinus Torvalds head = page_buffers(page); 18561da177e4SLinus Torvalds 18571da177e4SLinus Torvalds bbits = inode->i_blkbits; 18581da177e4SLinus Torvalds block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); 18591da177e4SLinus Torvalds 18601da177e4SLinus Torvalds for(bh = head, block_start = 0; bh != head || !block_start; 18611da177e4SLinus Torvalds block++, block_start=block_end, bh = bh->b_this_page) { 18621da177e4SLinus Torvalds block_end = block_start + blocksize; 18631da177e4SLinus Torvalds if (block_end <= from || block_start >= to) { 18641da177e4SLinus Torvalds if (PageUptodate(page)) { 18651da177e4SLinus Torvalds if (!buffer_uptodate(bh)) 18661da177e4SLinus Torvalds set_buffer_uptodate(bh); 18671da177e4SLinus Torvalds } 18681da177e4SLinus Torvalds continue; 18691da177e4SLinus Torvalds } 18701da177e4SLinus Torvalds if (buffer_new(bh)) 18711da177e4SLinus Torvalds clear_buffer_new(bh); 18721da177e4SLinus Torvalds if (!buffer_mapped(bh)) { 1873b0cf2321SBadari Pulavarty WARN_ON(bh->b_size != blocksize); 18741da177e4SLinus Torvalds err = get_block(inode, block, bh, 1); 18751da177e4SLinus Torvalds if (err) 1876f3ddbdc6SNick Piggin break; 18771da177e4SLinus Torvalds if (buffer_new(bh)) { 18781da177e4SLinus Torvalds unmap_underlying_metadata(bh->b_bdev, 18791da177e4SLinus Torvalds bh->b_blocknr); 18801da177e4SLinus Torvalds if (PageUptodate(page)) { 1881637aff46SNick Piggin clear_buffer_new(bh); 18821da177e4SLinus Torvalds set_buffer_uptodate(bh); 1883637aff46SNick Piggin mark_buffer_dirty(bh); 18841da177e4SLinus Torvalds continue; 18851da177e4SLinus Torvalds } 1886eebd2aa3SChristoph Lameter if (block_end > to || block_start < from) 1887eebd2aa3SChristoph Lameter zero_user_segments(page, 1888eebd2aa3SChristoph Lameter to, block_end, 1889eebd2aa3SChristoph Lameter block_start, from); 18901da177e4SLinus Torvalds continue; 18911da177e4SLinus Torvalds } 18921da177e4SLinus Torvalds } 18931da177e4SLinus Torvalds if (PageUptodate(page)) { 18941da177e4SLinus Torvalds if (!buffer_uptodate(bh)) 18951da177e4SLinus Torvalds set_buffer_uptodate(bh); 18961da177e4SLinus Torvalds continue; 18971da177e4SLinus Torvalds } 18981da177e4SLinus Torvalds if (!buffer_uptodate(bh) && !buffer_delay(bh) && 189933a266ddSDavid Chinner !buffer_unwritten(bh) && 19001da177e4SLinus Torvalds (block_start < from || block_end > to)) { 19011da177e4SLinus Torvalds ll_rw_block(READ, 1, &bh); 19021da177e4SLinus Torvalds *wait_bh++=bh; 19031da177e4SLinus Torvalds } 19041da177e4SLinus Torvalds } 19051da177e4SLinus Torvalds /* 19061da177e4SLinus Torvalds * If we issued read requests - let them complete. 19071da177e4SLinus Torvalds */ 19081da177e4SLinus Torvalds while(wait_bh > wait) { 19091da177e4SLinus Torvalds wait_on_buffer(*--wait_bh); 19101da177e4SLinus Torvalds if (!buffer_uptodate(*wait_bh)) 1911f3ddbdc6SNick Piggin err = -EIO; 19121da177e4SLinus Torvalds } 19136e1db88dSChristoph Hellwig if (unlikely(err)) { 1914afddba49SNick Piggin page_zero_new_buffers(page, from, to); 19156e1db88dSChristoph Hellwig ClearPageUptodate(page); 19166e1db88dSChristoph Hellwig } 19171da177e4SLinus Torvalds return err; 19181da177e4SLinus Torvalds } 19196e1db88dSChristoph Hellwig EXPORT_SYMBOL(block_prepare_write); 19201da177e4SLinus Torvalds 19211da177e4SLinus Torvalds static int __block_commit_write(struct inode *inode, struct page *page, 19221da177e4SLinus Torvalds unsigned from, unsigned to) 19231da177e4SLinus Torvalds { 19241da177e4SLinus Torvalds unsigned block_start, block_end; 19251da177e4SLinus Torvalds int partial = 0; 19261da177e4SLinus Torvalds unsigned blocksize; 19271da177e4SLinus Torvalds struct buffer_head *bh, *head; 19281da177e4SLinus Torvalds 19291da177e4SLinus Torvalds blocksize = 1 << inode->i_blkbits; 19301da177e4SLinus Torvalds 19311da177e4SLinus Torvalds for(bh = head = page_buffers(page), block_start = 0; 19321da177e4SLinus Torvalds bh != head || !block_start; 19331da177e4SLinus Torvalds block_start=block_end, bh = bh->b_this_page) { 19341da177e4SLinus Torvalds block_end = block_start + blocksize; 19351da177e4SLinus Torvalds if (block_end <= from || block_start >= to) { 19361da177e4SLinus Torvalds if (!buffer_uptodate(bh)) 19371da177e4SLinus Torvalds partial = 1; 19381da177e4SLinus Torvalds } else { 19391da177e4SLinus Torvalds set_buffer_uptodate(bh); 19401da177e4SLinus Torvalds mark_buffer_dirty(bh); 19411da177e4SLinus Torvalds } 1942afddba49SNick Piggin clear_buffer_new(bh); 19431da177e4SLinus Torvalds } 19441da177e4SLinus Torvalds 19451da177e4SLinus Torvalds /* 19461da177e4SLinus Torvalds * If this is a partial write which happened to make all buffers 19471da177e4SLinus Torvalds * uptodate then we can optimize away a bogus readpage() for 19481da177e4SLinus Torvalds * the next read(). Here we 'discover' whether the page went 19491da177e4SLinus Torvalds * uptodate as a result of this (potentially partial) write. 19501da177e4SLinus Torvalds */ 19511da177e4SLinus Torvalds if (!partial) 19521da177e4SLinus Torvalds SetPageUptodate(page); 19531da177e4SLinus Torvalds return 0; 19541da177e4SLinus Torvalds } 19551da177e4SLinus Torvalds 19566e1db88dSChristoph Hellwig int __block_write_begin(struct page *page, loff_t pos, unsigned len, 19576e1db88dSChristoph Hellwig get_block_t *get_block) 19586e1db88dSChristoph Hellwig { 19596e1db88dSChristoph Hellwig unsigned start = pos & (PAGE_CACHE_SIZE - 1); 19606e1db88dSChristoph Hellwig 19616e1db88dSChristoph Hellwig return block_prepare_write(page, start, start + len, get_block); 19626e1db88dSChristoph Hellwig } 19636e1db88dSChristoph Hellwig EXPORT_SYMBOL(__block_write_begin); 19646e1db88dSChristoph Hellwig 19651da177e4SLinus Torvalds /* 1966155130a4SChristoph Hellwig * block_write_begin takes care of the basic task of block allocation and 1967155130a4SChristoph Hellwig * bringing partial write blocks uptodate first. 1968155130a4SChristoph Hellwig * 19697bb46a67Snpiggin@suse.de * The filesystem needs to handle block truncation upon failure. 1970afddba49SNick Piggin */ 1971155130a4SChristoph Hellwig int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, 1972155130a4SChristoph Hellwig unsigned flags, struct page **pagep, get_block_t *get_block) 1973afddba49SNick Piggin { 19746e1db88dSChristoph Hellwig pgoff_t index = pos >> PAGE_CACHE_SHIFT; 1975afddba49SNick Piggin struct page *page; 19766e1db88dSChristoph Hellwig int status; 1977afddba49SNick Piggin 197854566b2cSNick Piggin page = grab_cache_page_write_begin(mapping, index, flags); 19796e1db88dSChristoph Hellwig if (!page) 19806e1db88dSChristoph Hellwig return -ENOMEM; 1981afddba49SNick Piggin 19826e1db88dSChristoph Hellwig status = __block_write_begin(page, pos, len, get_block); 1983afddba49SNick Piggin if (unlikely(status)) { 1984afddba49SNick Piggin unlock_page(page); 1985afddba49SNick Piggin page_cache_release(page); 19866e1db88dSChristoph Hellwig page = NULL; 1987afddba49SNick Piggin } 1988afddba49SNick Piggin 19896e1db88dSChristoph Hellwig *pagep = page; 1990afddba49SNick Piggin return status; 1991afddba49SNick Piggin } 1992afddba49SNick Piggin EXPORT_SYMBOL(block_write_begin); 1993afddba49SNick Piggin 1994afddba49SNick Piggin int block_write_end(struct file *file, struct address_space *mapping, 1995afddba49SNick Piggin loff_t pos, unsigned len, unsigned copied, 1996afddba49SNick Piggin struct page *page, void *fsdata) 1997afddba49SNick Piggin { 1998afddba49SNick Piggin struct inode *inode = mapping->host; 1999afddba49SNick Piggin unsigned start; 2000afddba49SNick Piggin 2001afddba49SNick Piggin start = pos & (PAGE_CACHE_SIZE - 1); 2002afddba49SNick Piggin 2003afddba49SNick Piggin if (unlikely(copied < len)) { 2004afddba49SNick Piggin /* 2005afddba49SNick Piggin * The buffers that were written will now be uptodate, so we 2006afddba49SNick Piggin * don't have to worry about a readpage reading them and 2007afddba49SNick Piggin * overwriting a partial write. However if we have encountered 2008afddba49SNick Piggin * a short write and only partially written into a buffer, it 2009afddba49SNick Piggin * will not be marked uptodate, so a readpage might come in and 2010afddba49SNick Piggin * destroy our partial write. 2011afddba49SNick Piggin * 2012afddba49SNick Piggin * Do the simplest thing, and just treat any short write to a 2013afddba49SNick Piggin * non uptodate page as a zero-length write, and force the 2014afddba49SNick Piggin * caller to redo the whole thing. 2015afddba49SNick Piggin */ 2016afddba49SNick Piggin if (!PageUptodate(page)) 2017afddba49SNick Piggin copied = 0; 2018afddba49SNick Piggin 2019afddba49SNick Piggin page_zero_new_buffers(page, start+copied, start+len); 2020afddba49SNick Piggin } 2021afddba49SNick Piggin flush_dcache_page(page); 2022afddba49SNick Piggin 2023afddba49SNick Piggin /* This could be a short (even 0-length) commit */ 2024afddba49SNick Piggin __block_commit_write(inode, page, start, start+copied); 2025afddba49SNick Piggin 2026afddba49SNick Piggin return copied; 2027afddba49SNick Piggin } 2028afddba49SNick Piggin EXPORT_SYMBOL(block_write_end); 2029afddba49SNick Piggin 2030afddba49SNick Piggin int generic_write_end(struct file *file, struct address_space *mapping, 2031afddba49SNick Piggin loff_t pos, unsigned len, unsigned copied, 2032afddba49SNick Piggin struct page *page, void *fsdata) 2033afddba49SNick Piggin { 2034afddba49SNick Piggin struct inode *inode = mapping->host; 2035c7d206b3SJan Kara int i_size_changed = 0; 2036afddba49SNick Piggin 2037afddba49SNick Piggin copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); 2038afddba49SNick Piggin 2039afddba49SNick Piggin /* 2040afddba49SNick Piggin * No need to use i_size_read() here, the i_size 2041afddba49SNick Piggin * cannot change under us because we hold i_mutex. 2042afddba49SNick Piggin * 2043afddba49SNick Piggin * But it's important to update i_size while still holding page lock: 2044afddba49SNick Piggin * page writeout could otherwise come in and zero beyond i_size. 2045afddba49SNick Piggin */ 2046afddba49SNick Piggin if (pos+copied > inode->i_size) { 2047afddba49SNick Piggin i_size_write(inode, pos+copied); 2048c7d206b3SJan Kara i_size_changed = 1; 2049afddba49SNick Piggin } 2050afddba49SNick Piggin 2051afddba49SNick Piggin unlock_page(page); 2052afddba49SNick Piggin page_cache_release(page); 2053afddba49SNick Piggin 2054c7d206b3SJan Kara /* 2055c7d206b3SJan Kara * Don't mark the inode dirty under page lock. First, it unnecessarily 2056c7d206b3SJan Kara * makes the holding time of page lock longer. Second, it forces lock 2057c7d206b3SJan Kara * ordering of page lock and transaction start for journaling 2058c7d206b3SJan Kara * filesystems. 2059c7d206b3SJan Kara */ 2060c7d206b3SJan Kara if (i_size_changed) 2061c7d206b3SJan Kara mark_inode_dirty(inode); 2062c7d206b3SJan Kara 2063afddba49SNick Piggin return copied; 2064afddba49SNick Piggin } 2065afddba49SNick Piggin EXPORT_SYMBOL(generic_write_end); 2066afddba49SNick Piggin 2067afddba49SNick Piggin /* 20688ab22b9aSHisashi Hifumi * block_is_partially_uptodate checks whether buffers within a page are 20698ab22b9aSHisashi Hifumi * uptodate or not. 20708ab22b9aSHisashi Hifumi * 20718ab22b9aSHisashi Hifumi * Returns true if all buffers which correspond to a file portion 20728ab22b9aSHisashi Hifumi * we want to read are uptodate. 20738ab22b9aSHisashi Hifumi */ 20748ab22b9aSHisashi Hifumi int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, 20758ab22b9aSHisashi Hifumi unsigned long from) 20768ab22b9aSHisashi Hifumi { 20778ab22b9aSHisashi Hifumi struct inode *inode = page->mapping->host; 20788ab22b9aSHisashi Hifumi unsigned block_start, block_end, blocksize; 20798ab22b9aSHisashi Hifumi unsigned to; 20808ab22b9aSHisashi Hifumi struct buffer_head *bh, *head; 20818ab22b9aSHisashi Hifumi int ret = 1; 20828ab22b9aSHisashi Hifumi 20838ab22b9aSHisashi Hifumi if (!page_has_buffers(page)) 20848ab22b9aSHisashi Hifumi return 0; 20858ab22b9aSHisashi Hifumi 20868ab22b9aSHisashi Hifumi blocksize = 1 << inode->i_blkbits; 20878ab22b9aSHisashi Hifumi to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count); 20888ab22b9aSHisashi Hifumi to = from + to; 20898ab22b9aSHisashi Hifumi if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) 20908ab22b9aSHisashi Hifumi return 0; 20918ab22b9aSHisashi Hifumi 20928ab22b9aSHisashi Hifumi head = page_buffers(page); 20938ab22b9aSHisashi Hifumi bh = head; 20948ab22b9aSHisashi Hifumi block_start = 0; 20958ab22b9aSHisashi Hifumi do { 20968ab22b9aSHisashi Hifumi block_end = block_start + blocksize; 20978ab22b9aSHisashi Hifumi if (block_end > from && block_start < to) { 20988ab22b9aSHisashi Hifumi if (!buffer_uptodate(bh)) { 20998ab22b9aSHisashi Hifumi ret = 0; 21008ab22b9aSHisashi Hifumi break; 21018ab22b9aSHisashi Hifumi } 21028ab22b9aSHisashi Hifumi if (block_end >= to) 21038ab22b9aSHisashi Hifumi break; 21048ab22b9aSHisashi Hifumi } 21058ab22b9aSHisashi Hifumi block_start = block_end; 21068ab22b9aSHisashi Hifumi bh = bh->b_this_page; 21078ab22b9aSHisashi Hifumi } while (bh != head); 21088ab22b9aSHisashi Hifumi 21098ab22b9aSHisashi Hifumi return ret; 21108ab22b9aSHisashi Hifumi } 21118ab22b9aSHisashi Hifumi EXPORT_SYMBOL(block_is_partially_uptodate); 21128ab22b9aSHisashi Hifumi 21138ab22b9aSHisashi Hifumi /* 21141da177e4SLinus Torvalds * Generic "read page" function for block devices that have the normal 21151da177e4SLinus Torvalds * get_block functionality. This is most of the block device filesystems. 21161da177e4SLinus Torvalds * Reads the page asynchronously --- the unlock_buffer() and 21171da177e4SLinus Torvalds * set/clear_buffer_uptodate() functions propagate buffer state into the 21181da177e4SLinus Torvalds * page struct once IO has completed. 21191da177e4SLinus Torvalds */ 21201da177e4SLinus Torvalds int block_read_full_page(struct page *page, get_block_t *get_block) 21211da177e4SLinus Torvalds { 21221da177e4SLinus Torvalds struct inode *inode = page->mapping->host; 21231da177e4SLinus Torvalds sector_t iblock, lblock; 21241da177e4SLinus Torvalds struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; 21251da177e4SLinus Torvalds unsigned int blocksize; 21261da177e4SLinus Torvalds int nr, i; 21271da177e4SLinus Torvalds int fully_mapped = 1; 21281da177e4SLinus Torvalds 2129cd7619d6SMatt Mackall BUG_ON(!PageLocked(page)); 21301da177e4SLinus Torvalds blocksize = 1 << inode->i_blkbits; 21311da177e4SLinus Torvalds if (!page_has_buffers(page)) 21321da177e4SLinus Torvalds create_empty_buffers(page, blocksize, 0); 21331da177e4SLinus Torvalds head = page_buffers(page); 21341da177e4SLinus Torvalds 21351da177e4SLinus Torvalds iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 21361da177e4SLinus Torvalds lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits; 21371da177e4SLinus Torvalds bh = head; 21381da177e4SLinus Torvalds nr = 0; 21391da177e4SLinus Torvalds i = 0; 21401da177e4SLinus Torvalds 21411da177e4SLinus Torvalds do { 21421da177e4SLinus Torvalds if (buffer_uptodate(bh)) 21431da177e4SLinus Torvalds continue; 21441da177e4SLinus Torvalds 21451da177e4SLinus Torvalds if (!buffer_mapped(bh)) { 2146c64610baSAndrew Morton int err = 0; 2147c64610baSAndrew Morton 21481da177e4SLinus Torvalds fully_mapped = 0; 21491da177e4SLinus Torvalds if (iblock < lblock) { 2150b0cf2321SBadari Pulavarty WARN_ON(bh->b_size != blocksize); 2151c64610baSAndrew Morton err = get_block(inode, iblock, bh, 0); 2152c64610baSAndrew Morton if (err) 21531da177e4SLinus Torvalds SetPageError(page); 21541da177e4SLinus Torvalds } 21551da177e4SLinus Torvalds if (!buffer_mapped(bh)) { 2156eebd2aa3SChristoph Lameter zero_user(page, i * blocksize, blocksize); 2157c64610baSAndrew Morton if (!err) 21581da177e4SLinus Torvalds set_buffer_uptodate(bh); 21591da177e4SLinus Torvalds continue; 21601da177e4SLinus Torvalds } 21611da177e4SLinus Torvalds /* 21621da177e4SLinus Torvalds * get_block() might have updated the buffer 21631da177e4SLinus Torvalds * synchronously 21641da177e4SLinus Torvalds */ 21651da177e4SLinus Torvalds if (buffer_uptodate(bh)) 21661da177e4SLinus Torvalds continue; 21671da177e4SLinus Torvalds } 21681da177e4SLinus Torvalds arr[nr++] = bh; 21691da177e4SLinus Torvalds } while (i++, iblock++, (bh = bh->b_this_page) != head); 21701da177e4SLinus Torvalds 21711da177e4SLinus Torvalds if (fully_mapped) 21721da177e4SLinus Torvalds SetPageMappedToDisk(page); 21731da177e4SLinus Torvalds 21741da177e4SLinus Torvalds if (!nr) { 21751da177e4SLinus Torvalds /* 21761da177e4SLinus Torvalds * All buffers are uptodate - we can set the page uptodate 21771da177e4SLinus Torvalds * as well. But not if get_block() returned an error. 21781da177e4SLinus Torvalds */ 21791da177e4SLinus Torvalds if (!PageError(page)) 21801da177e4SLinus Torvalds SetPageUptodate(page); 21811da177e4SLinus Torvalds unlock_page(page); 21821da177e4SLinus Torvalds return 0; 21831da177e4SLinus Torvalds } 21841da177e4SLinus Torvalds 21851da177e4SLinus Torvalds /* Stage two: lock the buffers */ 21861da177e4SLinus Torvalds for (i = 0; i < nr; i++) { 21871da177e4SLinus Torvalds bh = arr[i]; 21881da177e4SLinus Torvalds lock_buffer(bh); 21891da177e4SLinus Torvalds mark_buffer_async_read(bh); 21901da177e4SLinus Torvalds } 21911da177e4SLinus Torvalds 21921da177e4SLinus Torvalds /* 21931da177e4SLinus Torvalds * Stage 3: start the IO. Check for uptodateness 21941da177e4SLinus Torvalds * inside the buffer lock in case another process reading 21951da177e4SLinus Torvalds * the underlying blockdev brought it uptodate (the sct fix). 21961da177e4SLinus Torvalds */ 21971da177e4SLinus Torvalds for (i = 0; i < nr; i++) { 21981da177e4SLinus Torvalds bh = arr[i]; 21991da177e4SLinus Torvalds if (buffer_uptodate(bh)) 22001da177e4SLinus Torvalds end_buffer_async_read(bh, 1); 22011da177e4SLinus Torvalds else 22021da177e4SLinus Torvalds submit_bh(READ, bh); 22031da177e4SLinus Torvalds } 22041da177e4SLinus Torvalds return 0; 22051da177e4SLinus Torvalds } 22061fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(block_read_full_page); 22071da177e4SLinus Torvalds 22081da177e4SLinus Torvalds /* utility function for filesystems that need to do work on expanding 220989e10787SNick Piggin * truncates. Uses filesystem pagecache writes to allow the filesystem to 22101da177e4SLinus Torvalds * deal with the hole. 22111da177e4SLinus Torvalds */ 221289e10787SNick Piggin int generic_cont_expand_simple(struct inode *inode, loff_t size) 22131da177e4SLinus Torvalds { 22141da177e4SLinus Torvalds struct address_space *mapping = inode->i_mapping; 22151da177e4SLinus Torvalds struct page *page; 221689e10787SNick Piggin void *fsdata; 22171da177e4SLinus Torvalds int err; 22181da177e4SLinus Torvalds 2219c08d3b0eSnpiggin@suse.de err = inode_newsize_ok(inode, size); 2220c08d3b0eSnpiggin@suse.de if (err) 22211da177e4SLinus Torvalds goto out; 22221da177e4SLinus Torvalds 222389e10787SNick Piggin err = pagecache_write_begin(NULL, mapping, size, 0, 222489e10787SNick Piggin AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, 222589e10787SNick Piggin &page, &fsdata); 222689e10787SNick Piggin if (err) 222705eb0b51SOGAWA Hirofumi goto out; 222805eb0b51SOGAWA Hirofumi 222989e10787SNick Piggin err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); 223089e10787SNick Piggin BUG_ON(err > 0); 223105eb0b51SOGAWA Hirofumi 223205eb0b51SOGAWA Hirofumi out: 223305eb0b51SOGAWA Hirofumi return err; 223405eb0b51SOGAWA Hirofumi } 22351fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(generic_cont_expand_simple); 223605eb0b51SOGAWA Hirofumi 2237f1e3af72SAdrian Bunk static int cont_expand_zero(struct file *file, struct address_space *mapping, 223889e10787SNick Piggin loff_t pos, loff_t *bytes) 223905eb0b51SOGAWA Hirofumi { 224089e10787SNick Piggin struct inode *inode = mapping->host; 224189e10787SNick Piggin unsigned blocksize = 1 << inode->i_blkbits; 224289e10787SNick Piggin struct page *page; 224389e10787SNick Piggin void *fsdata; 224489e10787SNick Piggin pgoff_t index, curidx; 224589e10787SNick Piggin loff_t curpos; 224689e10787SNick Piggin unsigned zerofrom, offset, len; 224789e10787SNick Piggin int err = 0; 224805eb0b51SOGAWA Hirofumi 224989e10787SNick Piggin index = pos >> PAGE_CACHE_SHIFT; 225089e10787SNick Piggin offset = pos & ~PAGE_CACHE_MASK; 225189e10787SNick Piggin 225289e10787SNick Piggin while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { 225389e10787SNick Piggin zerofrom = curpos & ~PAGE_CACHE_MASK; 225489e10787SNick Piggin if (zerofrom & (blocksize-1)) { 225589e10787SNick Piggin *bytes |= (blocksize-1); 225689e10787SNick Piggin (*bytes)++; 225789e10787SNick Piggin } 225889e10787SNick Piggin len = PAGE_CACHE_SIZE - zerofrom; 225989e10787SNick Piggin 226089e10787SNick Piggin err = pagecache_write_begin(file, mapping, curpos, len, 226189e10787SNick Piggin AOP_FLAG_UNINTERRUPTIBLE, 226289e10787SNick Piggin &page, &fsdata); 226389e10787SNick Piggin if (err) 226489e10787SNick Piggin goto out; 2265eebd2aa3SChristoph Lameter zero_user(page, zerofrom, len); 226689e10787SNick Piggin err = pagecache_write_end(file, mapping, curpos, len, len, 226789e10787SNick Piggin page, fsdata); 226889e10787SNick Piggin if (err < 0) 226989e10787SNick Piggin goto out; 227089e10787SNick Piggin BUG_ON(err != len); 227189e10787SNick Piggin err = 0; 2272061e9746SOGAWA Hirofumi 2273061e9746SOGAWA Hirofumi balance_dirty_pages_ratelimited(mapping); 227489e10787SNick Piggin } 227589e10787SNick Piggin 227689e10787SNick Piggin /* page covers the boundary, find the boundary offset */ 227789e10787SNick Piggin if (index == curidx) { 227889e10787SNick Piggin zerofrom = curpos & ~PAGE_CACHE_MASK; 227989e10787SNick Piggin /* if we will expand the thing last block will be filled */ 228089e10787SNick Piggin if (offset <= zerofrom) { 228189e10787SNick Piggin goto out; 228289e10787SNick Piggin } 228389e10787SNick Piggin if (zerofrom & (blocksize-1)) { 228489e10787SNick Piggin *bytes |= (blocksize-1); 228589e10787SNick Piggin (*bytes)++; 228689e10787SNick Piggin } 228789e10787SNick Piggin len = offset - zerofrom; 228889e10787SNick Piggin 228989e10787SNick Piggin err = pagecache_write_begin(file, mapping, curpos, len, 229089e10787SNick Piggin AOP_FLAG_UNINTERRUPTIBLE, 229189e10787SNick Piggin &page, &fsdata); 229289e10787SNick Piggin if (err) 229389e10787SNick Piggin goto out; 2294eebd2aa3SChristoph Lameter zero_user(page, zerofrom, len); 229589e10787SNick Piggin err = pagecache_write_end(file, mapping, curpos, len, len, 229689e10787SNick Piggin page, fsdata); 229789e10787SNick Piggin if (err < 0) 229889e10787SNick Piggin goto out; 229989e10787SNick Piggin BUG_ON(err != len); 230089e10787SNick Piggin err = 0; 230189e10787SNick Piggin } 230289e10787SNick Piggin out: 230389e10787SNick Piggin return err; 23041da177e4SLinus Torvalds } 23051da177e4SLinus Torvalds 23061da177e4SLinus Torvalds /* 23071da177e4SLinus Torvalds * For moronic filesystems that do not allow holes in file. 23081da177e4SLinus Torvalds * We may have to extend the file. 23091da177e4SLinus Torvalds */ 2310282dc178SChristoph Hellwig int cont_write_begin(struct file *file, struct address_space *mapping, 231189e10787SNick Piggin loff_t pos, unsigned len, unsigned flags, 231289e10787SNick Piggin struct page **pagep, void **fsdata, 231389e10787SNick Piggin get_block_t *get_block, loff_t *bytes) 23141da177e4SLinus Torvalds { 23151da177e4SLinus Torvalds struct inode *inode = mapping->host; 23161da177e4SLinus Torvalds unsigned blocksize = 1 << inode->i_blkbits; 231789e10787SNick Piggin unsigned zerofrom; 231889e10787SNick Piggin int err; 23191da177e4SLinus Torvalds 232089e10787SNick Piggin err = cont_expand_zero(file, mapping, pos, bytes); 232189e10787SNick Piggin if (err) 2322155130a4SChristoph Hellwig return err; 23231da177e4SLinus Torvalds 23241da177e4SLinus Torvalds zerofrom = *bytes & ~PAGE_CACHE_MASK; 232589e10787SNick Piggin if (pos+len > *bytes && zerofrom & (blocksize-1)) { 23261da177e4SLinus Torvalds *bytes |= (blocksize-1); 23271da177e4SLinus Torvalds (*bytes)++; 23281da177e4SLinus Torvalds } 23291da177e4SLinus Torvalds 2330155130a4SChristoph Hellwig return block_write_begin(mapping, pos, len, flags, pagep, get_block); 23311da177e4SLinus Torvalds } 23321fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(cont_write_begin); 23331da177e4SLinus Torvalds 23341da177e4SLinus Torvalds int block_commit_write(struct page *page, unsigned from, unsigned to) 23351da177e4SLinus Torvalds { 23361da177e4SLinus Torvalds struct inode *inode = page->mapping->host; 23371da177e4SLinus Torvalds __block_commit_write(inode,page,from,to); 23381da177e4SLinus Torvalds return 0; 23391da177e4SLinus Torvalds } 23401fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(block_commit_write); 23411da177e4SLinus Torvalds 234254171690SDavid Chinner /* 234354171690SDavid Chinner * block_page_mkwrite() is not allowed to change the file size as it gets 234454171690SDavid Chinner * called from a page fault handler when a page is first dirtied. Hence we must 234554171690SDavid Chinner * be careful to check for EOF conditions here. We set the page up correctly 234654171690SDavid Chinner * for a written page which means we get ENOSPC checking when writing into 234754171690SDavid Chinner * holes and correct delalloc and unwritten extent mapping on filesystems that 234854171690SDavid Chinner * support these features. 234954171690SDavid Chinner * 235054171690SDavid Chinner * We are not allowed to take the i_mutex here so we have to play games to 235154171690SDavid Chinner * protect against truncate races as the page could now be beyond EOF. Because 23527bb46a67Snpiggin@suse.de * truncate writes the inode size before removing pages, once we have the 235354171690SDavid Chinner * page lock we can determine safely if the page is beyond EOF. If it is not 235454171690SDavid Chinner * beyond EOF, then the page is guaranteed safe against truncation until we 235554171690SDavid Chinner * unlock the page. 235654171690SDavid Chinner */ 235754171690SDavid Chinner int 2358c2ec175cSNick Piggin block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 235954171690SDavid Chinner get_block_t get_block) 236054171690SDavid Chinner { 2361c2ec175cSNick Piggin struct page *page = vmf->page; 236254171690SDavid Chinner struct inode *inode = vma->vm_file->f_path.dentry->d_inode; 236354171690SDavid Chinner unsigned long end; 236454171690SDavid Chinner loff_t size; 236556a76f82SNick Piggin int ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */ 236654171690SDavid Chinner 236754171690SDavid Chinner lock_page(page); 236854171690SDavid Chinner size = i_size_read(inode); 236954171690SDavid Chinner if ((page->mapping != inode->i_mapping) || 237018336338SNick Piggin (page_offset(page) > size)) { 237154171690SDavid Chinner /* page got truncated out from underneath us */ 2372b827e496SNick Piggin unlock_page(page); 2373b827e496SNick Piggin goto out; 237454171690SDavid Chinner } 237554171690SDavid Chinner 237654171690SDavid Chinner /* page is wholly or partially inside EOF */ 237754171690SDavid Chinner if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) 237854171690SDavid Chinner end = size & ~PAGE_CACHE_MASK; 237954171690SDavid Chinner else 238054171690SDavid Chinner end = PAGE_CACHE_SIZE; 238154171690SDavid Chinner 238254171690SDavid Chinner ret = block_prepare_write(page, 0, end, get_block); 238354171690SDavid Chinner if (!ret) 238454171690SDavid Chinner ret = block_commit_write(page, 0, end); 238554171690SDavid Chinner 238656a76f82SNick Piggin if (unlikely(ret)) { 2387b827e496SNick Piggin unlock_page(page); 238856a76f82SNick Piggin if (ret == -ENOMEM) 238956a76f82SNick Piggin ret = VM_FAULT_OOM; 239056a76f82SNick Piggin else /* -ENOSPC, -EIO, etc */ 2391c2ec175cSNick Piggin ret = VM_FAULT_SIGBUS; 2392b827e496SNick Piggin } else 2393b827e496SNick Piggin ret = VM_FAULT_LOCKED; 2394c2ec175cSNick Piggin 2395b827e496SNick Piggin out: 239654171690SDavid Chinner return ret; 239754171690SDavid Chinner } 23981fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(block_page_mkwrite); 23991da177e4SLinus Torvalds 24001da177e4SLinus Torvalds /* 240103158cd7SNick Piggin * nobh_write_begin()'s prereads are special: the buffer_heads are freed 24021da177e4SLinus Torvalds * immediately, while under the page lock. So it needs a special end_io 24031da177e4SLinus Torvalds * handler which does not touch the bh after unlocking it. 24041da177e4SLinus Torvalds */ 24051da177e4SLinus Torvalds static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) 24061da177e4SLinus Torvalds { 240768671f35SDmitry Monakhov __end_buffer_read_notouch(bh, uptodate); 24081da177e4SLinus Torvalds } 24091da177e4SLinus Torvalds 24101da177e4SLinus Torvalds /* 241103158cd7SNick Piggin * Attach the singly-linked list of buffers created by nobh_write_begin, to 241203158cd7SNick Piggin * the page (converting it to circular linked list and taking care of page 241303158cd7SNick Piggin * dirty races). 241403158cd7SNick Piggin */ 241503158cd7SNick Piggin static void attach_nobh_buffers(struct page *page, struct buffer_head *head) 241603158cd7SNick Piggin { 241703158cd7SNick Piggin struct buffer_head *bh; 241803158cd7SNick Piggin 241903158cd7SNick Piggin BUG_ON(!PageLocked(page)); 242003158cd7SNick Piggin 242103158cd7SNick Piggin spin_lock(&page->mapping->private_lock); 242203158cd7SNick Piggin bh = head; 242303158cd7SNick Piggin do { 242403158cd7SNick Piggin if (PageDirty(page)) 242503158cd7SNick Piggin set_buffer_dirty(bh); 242603158cd7SNick Piggin if (!bh->b_this_page) 242703158cd7SNick Piggin bh->b_this_page = head; 242803158cd7SNick Piggin bh = bh->b_this_page; 242903158cd7SNick Piggin } while (bh != head); 243003158cd7SNick Piggin attach_page_buffers(page, head); 243103158cd7SNick Piggin spin_unlock(&page->mapping->private_lock); 243203158cd7SNick Piggin } 243303158cd7SNick Piggin 243403158cd7SNick Piggin /* 2435ea0f04e5SChristoph Hellwig * On entry, the page is fully not uptodate. 2436ea0f04e5SChristoph Hellwig * On exit the page is fully uptodate in the areas outside (from,to) 24377bb46a67Snpiggin@suse.de * The filesystem needs to handle block truncation upon failure. 24381da177e4SLinus Torvalds */ 2439ea0f04e5SChristoph Hellwig int nobh_write_begin(struct address_space *mapping, 244003158cd7SNick Piggin loff_t pos, unsigned len, unsigned flags, 244103158cd7SNick Piggin struct page **pagep, void **fsdata, 24421da177e4SLinus Torvalds get_block_t *get_block) 24431da177e4SLinus Torvalds { 244403158cd7SNick Piggin struct inode *inode = mapping->host; 24451da177e4SLinus Torvalds const unsigned blkbits = inode->i_blkbits; 24461da177e4SLinus Torvalds const unsigned blocksize = 1 << blkbits; 2447a4b0672dSNick Piggin struct buffer_head *head, *bh; 244803158cd7SNick Piggin struct page *page; 244903158cd7SNick Piggin pgoff_t index; 245003158cd7SNick Piggin unsigned from, to; 24511da177e4SLinus Torvalds unsigned block_in_page; 2452a4b0672dSNick Piggin unsigned block_start, block_end; 24531da177e4SLinus Torvalds sector_t block_in_file; 24541da177e4SLinus Torvalds int nr_reads = 0; 24551da177e4SLinus Torvalds int ret = 0; 24561da177e4SLinus Torvalds int is_mapped_to_disk = 1; 24571da177e4SLinus Torvalds 245803158cd7SNick Piggin index = pos >> PAGE_CACHE_SHIFT; 245903158cd7SNick Piggin from = pos & (PAGE_CACHE_SIZE - 1); 246003158cd7SNick Piggin to = from + len; 246103158cd7SNick Piggin 246254566b2cSNick Piggin page = grab_cache_page_write_begin(mapping, index, flags); 246303158cd7SNick Piggin if (!page) 246403158cd7SNick Piggin return -ENOMEM; 246503158cd7SNick Piggin *pagep = page; 246603158cd7SNick Piggin *fsdata = NULL; 246703158cd7SNick Piggin 246803158cd7SNick Piggin if (page_has_buffers(page)) { 246903158cd7SNick Piggin unlock_page(page); 247003158cd7SNick Piggin page_cache_release(page); 247103158cd7SNick Piggin *pagep = NULL; 2472155130a4SChristoph Hellwig return block_write_begin(mapping, pos, len, flags, pagep, 2473155130a4SChristoph Hellwig get_block); 247403158cd7SNick Piggin } 2475a4b0672dSNick Piggin 24761da177e4SLinus Torvalds if (PageMappedToDisk(page)) 24771da177e4SLinus Torvalds return 0; 24781da177e4SLinus Torvalds 2479a4b0672dSNick Piggin /* 2480a4b0672dSNick Piggin * Allocate buffers so that we can keep track of state, and potentially 2481a4b0672dSNick Piggin * attach them to the page if an error occurs. In the common case of 2482a4b0672dSNick Piggin * no error, they will just be freed again without ever being attached 2483a4b0672dSNick Piggin * to the page (which is all OK, because we're under the page lock). 2484a4b0672dSNick Piggin * 2485a4b0672dSNick Piggin * Be careful: the buffer linked list is a NULL terminated one, rather 2486a4b0672dSNick Piggin * than the circular one we're used to. 2487a4b0672dSNick Piggin */ 2488a4b0672dSNick Piggin head = alloc_page_buffers(page, blocksize, 0); 248903158cd7SNick Piggin if (!head) { 249003158cd7SNick Piggin ret = -ENOMEM; 249103158cd7SNick Piggin goto out_release; 249203158cd7SNick Piggin } 2493a4b0672dSNick Piggin 24941da177e4SLinus Torvalds block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); 24951da177e4SLinus Torvalds 24961da177e4SLinus Torvalds /* 24971da177e4SLinus Torvalds * We loop across all blocks in the page, whether or not they are 24981da177e4SLinus Torvalds * part of the affected region. This is so we can discover if the 24991da177e4SLinus Torvalds * page is fully mapped-to-disk. 25001da177e4SLinus Torvalds */ 2501a4b0672dSNick Piggin for (block_start = 0, block_in_page = 0, bh = head; 25021da177e4SLinus Torvalds block_start < PAGE_CACHE_SIZE; 2503a4b0672dSNick Piggin block_in_page++, block_start += blocksize, bh = bh->b_this_page) { 25041da177e4SLinus Torvalds int create; 25051da177e4SLinus Torvalds 2506a4b0672dSNick Piggin block_end = block_start + blocksize; 2507a4b0672dSNick Piggin bh->b_state = 0; 25081da177e4SLinus Torvalds create = 1; 25091da177e4SLinus Torvalds if (block_start >= to) 25101da177e4SLinus Torvalds create = 0; 25111da177e4SLinus Torvalds ret = get_block(inode, block_in_file + block_in_page, 2512a4b0672dSNick Piggin bh, create); 25131da177e4SLinus Torvalds if (ret) 25141da177e4SLinus Torvalds goto failed; 2515a4b0672dSNick Piggin if (!buffer_mapped(bh)) 25161da177e4SLinus Torvalds is_mapped_to_disk = 0; 2517a4b0672dSNick Piggin if (buffer_new(bh)) 2518a4b0672dSNick Piggin unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); 2519a4b0672dSNick Piggin if (PageUptodate(page)) { 2520a4b0672dSNick Piggin set_buffer_uptodate(bh); 25211da177e4SLinus Torvalds continue; 2522a4b0672dSNick Piggin } 2523a4b0672dSNick Piggin if (buffer_new(bh) || !buffer_mapped(bh)) { 2524eebd2aa3SChristoph Lameter zero_user_segments(page, block_start, from, 2525eebd2aa3SChristoph Lameter to, block_end); 25261da177e4SLinus Torvalds continue; 25271da177e4SLinus Torvalds } 2528a4b0672dSNick Piggin if (buffer_uptodate(bh)) 25291da177e4SLinus Torvalds continue; /* reiserfs does this */ 25301da177e4SLinus Torvalds if (block_start < from || block_end > to) { 2531a4b0672dSNick Piggin lock_buffer(bh); 2532a4b0672dSNick Piggin bh->b_end_io = end_buffer_read_nobh; 2533a4b0672dSNick Piggin submit_bh(READ, bh); 2534a4b0672dSNick Piggin nr_reads++; 25351da177e4SLinus Torvalds } 25361da177e4SLinus Torvalds } 25371da177e4SLinus Torvalds 25381da177e4SLinus Torvalds if (nr_reads) { 25391da177e4SLinus Torvalds /* 25401da177e4SLinus Torvalds * The page is locked, so these buffers are protected from 25411da177e4SLinus Torvalds * any VM or truncate activity. Hence we don't need to care 25421da177e4SLinus Torvalds * for the buffer_head refcounts. 25431da177e4SLinus Torvalds */ 2544a4b0672dSNick Piggin for (bh = head; bh; bh = bh->b_this_page) { 25451da177e4SLinus Torvalds wait_on_buffer(bh); 25461da177e4SLinus Torvalds if (!buffer_uptodate(bh)) 25471da177e4SLinus Torvalds ret = -EIO; 25481da177e4SLinus Torvalds } 25491da177e4SLinus Torvalds if (ret) 25501da177e4SLinus Torvalds goto failed; 25511da177e4SLinus Torvalds } 25521da177e4SLinus Torvalds 25531da177e4SLinus Torvalds if (is_mapped_to_disk) 25541da177e4SLinus Torvalds SetPageMappedToDisk(page); 25551da177e4SLinus Torvalds 255603158cd7SNick Piggin *fsdata = head; /* to be released by nobh_write_end */ 2557a4b0672dSNick Piggin 25581da177e4SLinus Torvalds return 0; 25591da177e4SLinus Torvalds 25601da177e4SLinus Torvalds failed: 256103158cd7SNick Piggin BUG_ON(!ret); 25621da177e4SLinus Torvalds /* 2563a4b0672dSNick Piggin * Error recovery is a bit difficult. We need to zero out blocks that 2564a4b0672dSNick Piggin * were newly allocated, and dirty them to ensure they get written out. 2565a4b0672dSNick Piggin * Buffers need to be attached to the page at this point, otherwise 2566a4b0672dSNick Piggin * the handling of potential IO errors during writeout would be hard 2567a4b0672dSNick Piggin * (could try doing synchronous writeout, but what if that fails too?) 25681da177e4SLinus Torvalds */ 256903158cd7SNick Piggin attach_nobh_buffers(page, head); 257003158cd7SNick Piggin page_zero_new_buffers(page, from, to); 2571a4b0672dSNick Piggin 257203158cd7SNick Piggin out_release: 257303158cd7SNick Piggin unlock_page(page); 257403158cd7SNick Piggin page_cache_release(page); 257503158cd7SNick Piggin *pagep = NULL; 2576a4b0672dSNick Piggin 25777bb46a67Snpiggin@suse.de return ret; 25787bb46a67Snpiggin@suse.de } 257903158cd7SNick Piggin EXPORT_SYMBOL(nobh_write_begin); 25801da177e4SLinus Torvalds 258103158cd7SNick Piggin int nobh_write_end(struct file *file, struct address_space *mapping, 258203158cd7SNick Piggin loff_t pos, unsigned len, unsigned copied, 258303158cd7SNick Piggin struct page *page, void *fsdata) 25841da177e4SLinus Torvalds { 25851da177e4SLinus Torvalds struct inode *inode = page->mapping->host; 2586efdc3131SNick Piggin struct buffer_head *head = fsdata; 258703158cd7SNick Piggin struct buffer_head *bh; 25885b41e74aSDmitri Monakhov BUG_ON(fsdata != NULL && page_has_buffers(page)); 25891da177e4SLinus Torvalds 2590d4cf109fSDave Kleikamp if (unlikely(copied < len) && head) 259103158cd7SNick Piggin attach_nobh_buffers(page, head); 2592a4b0672dSNick Piggin if (page_has_buffers(page)) 259303158cd7SNick Piggin return generic_write_end(file, mapping, pos, len, 259403158cd7SNick Piggin copied, page, fsdata); 2595a4b0672dSNick Piggin 259622c8ca78SNick Piggin SetPageUptodate(page); 25971da177e4SLinus Torvalds set_page_dirty(page); 259803158cd7SNick Piggin if (pos+copied > inode->i_size) { 259903158cd7SNick Piggin i_size_write(inode, pos+copied); 26001da177e4SLinus Torvalds mark_inode_dirty(inode); 26011da177e4SLinus Torvalds } 260203158cd7SNick Piggin 260303158cd7SNick Piggin unlock_page(page); 260403158cd7SNick Piggin page_cache_release(page); 260503158cd7SNick Piggin 260603158cd7SNick Piggin while (head) { 260703158cd7SNick Piggin bh = head; 260803158cd7SNick Piggin head = head->b_this_page; 260903158cd7SNick Piggin free_buffer_head(bh); 26101da177e4SLinus Torvalds } 261103158cd7SNick Piggin 261203158cd7SNick Piggin return copied; 261303158cd7SNick Piggin } 261403158cd7SNick Piggin EXPORT_SYMBOL(nobh_write_end); 26151da177e4SLinus Torvalds 26161da177e4SLinus Torvalds /* 26171da177e4SLinus Torvalds * nobh_writepage() - based on block_full_write_page() except 26181da177e4SLinus Torvalds * that it tries to operate without attaching bufferheads to 26191da177e4SLinus Torvalds * the page. 26201da177e4SLinus Torvalds */ 26211da177e4SLinus Torvalds int nobh_writepage(struct page *page, get_block_t *get_block, 26221da177e4SLinus Torvalds struct writeback_control *wbc) 26231da177e4SLinus Torvalds { 26241da177e4SLinus Torvalds struct inode * const inode = page->mapping->host; 26251da177e4SLinus Torvalds loff_t i_size = i_size_read(inode); 26261da177e4SLinus Torvalds const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; 26271da177e4SLinus Torvalds unsigned offset; 26281da177e4SLinus Torvalds int ret; 26291da177e4SLinus Torvalds 26301da177e4SLinus Torvalds /* Is the page fully inside i_size? */ 26311da177e4SLinus Torvalds if (page->index < end_index) 26321da177e4SLinus Torvalds goto out; 26331da177e4SLinus Torvalds 26341da177e4SLinus Torvalds /* Is the page fully outside i_size? (truncate in progress) */ 26351da177e4SLinus Torvalds offset = i_size & (PAGE_CACHE_SIZE-1); 26361da177e4SLinus Torvalds if (page->index >= end_index+1 || !offset) { 26371da177e4SLinus Torvalds /* 26381da177e4SLinus Torvalds * The page may have dirty, unmapped buffers. For example, 26391da177e4SLinus Torvalds * they may have been added in ext3_writepage(). Make them 26401da177e4SLinus Torvalds * freeable here, so the page does not leak. 26411da177e4SLinus Torvalds */ 26421da177e4SLinus Torvalds #if 0 26431da177e4SLinus Torvalds /* Not really sure about this - do we need this ? */ 26441da177e4SLinus Torvalds if (page->mapping->a_ops->invalidatepage) 26451da177e4SLinus Torvalds page->mapping->a_ops->invalidatepage(page, offset); 26461da177e4SLinus Torvalds #endif 26471da177e4SLinus Torvalds unlock_page(page); 26481da177e4SLinus Torvalds return 0; /* don't care */ 26491da177e4SLinus Torvalds } 26501da177e4SLinus Torvalds 26511da177e4SLinus Torvalds /* 26521da177e4SLinus Torvalds * The page straddles i_size. It must be zeroed out on each and every 26531da177e4SLinus Torvalds * writepage invocation because it may be mmapped. "A file is mapped 26541da177e4SLinus Torvalds * in multiples of the page size. For a file that is not a multiple of 26551da177e4SLinus Torvalds * the page size, the remaining memory is zeroed when mapped, and 26561da177e4SLinus Torvalds * writes to that region are not written out to the file." 26571da177e4SLinus Torvalds */ 2658eebd2aa3SChristoph Lameter zero_user_segment(page, offset, PAGE_CACHE_SIZE); 26591da177e4SLinus Torvalds out: 26601da177e4SLinus Torvalds ret = mpage_writepage(page, get_block, wbc); 26611da177e4SLinus Torvalds if (ret == -EAGAIN) 266235c80d5fSChris Mason ret = __block_write_full_page(inode, page, get_block, wbc, 266335c80d5fSChris Mason end_buffer_async_write); 26641da177e4SLinus Torvalds return ret; 26651da177e4SLinus Torvalds } 26661da177e4SLinus Torvalds EXPORT_SYMBOL(nobh_writepage); 26671da177e4SLinus Torvalds 266803158cd7SNick Piggin int nobh_truncate_page(struct address_space *mapping, 266903158cd7SNick Piggin loff_t from, get_block_t *get_block) 26701da177e4SLinus Torvalds { 26711da177e4SLinus Torvalds pgoff_t index = from >> PAGE_CACHE_SHIFT; 26721da177e4SLinus Torvalds unsigned offset = from & (PAGE_CACHE_SIZE-1); 267303158cd7SNick Piggin unsigned blocksize; 267403158cd7SNick Piggin sector_t iblock; 267503158cd7SNick Piggin unsigned length, pos; 267603158cd7SNick Piggin struct inode *inode = mapping->host; 26771da177e4SLinus Torvalds struct page *page; 267803158cd7SNick Piggin struct buffer_head map_bh; 267903158cd7SNick Piggin int err; 26801da177e4SLinus Torvalds 268103158cd7SNick Piggin blocksize = 1 << inode->i_blkbits; 268203158cd7SNick Piggin length = offset & (blocksize - 1); 26831da177e4SLinus Torvalds 268403158cd7SNick Piggin /* Block boundary? Nothing to do */ 268503158cd7SNick Piggin if (!length) 268603158cd7SNick Piggin return 0; 268703158cd7SNick Piggin 268803158cd7SNick Piggin length = blocksize - length; 268903158cd7SNick Piggin iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 269003158cd7SNick Piggin 26911da177e4SLinus Torvalds page = grab_cache_page(mapping, index); 269203158cd7SNick Piggin err = -ENOMEM; 26931da177e4SLinus Torvalds if (!page) 26941da177e4SLinus Torvalds goto out; 26951da177e4SLinus Torvalds 269603158cd7SNick Piggin if (page_has_buffers(page)) { 269703158cd7SNick Piggin has_buffers: 269803158cd7SNick Piggin unlock_page(page); 269903158cd7SNick Piggin page_cache_release(page); 270003158cd7SNick Piggin return block_truncate_page(mapping, from, get_block); 27011da177e4SLinus Torvalds } 270203158cd7SNick Piggin 270303158cd7SNick Piggin /* Find the buffer that contains "offset" */ 270403158cd7SNick Piggin pos = blocksize; 270503158cd7SNick Piggin while (offset >= pos) { 270603158cd7SNick Piggin iblock++; 270703158cd7SNick Piggin pos += blocksize; 270803158cd7SNick Piggin } 270903158cd7SNick Piggin 2710460bcf57STheodore Ts'o map_bh.b_size = blocksize; 2711460bcf57STheodore Ts'o map_bh.b_state = 0; 271203158cd7SNick Piggin err = get_block(inode, iblock, &map_bh, 0); 271303158cd7SNick Piggin if (err) 271403158cd7SNick Piggin goto unlock; 271503158cd7SNick Piggin /* unmapped? It's a hole - nothing to do */ 271603158cd7SNick Piggin if (!buffer_mapped(&map_bh)) 271703158cd7SNick Piggin goto unlock; 271803158cd7SNick Piggin 271903158cd7SNick Piggin /* Ok, it's mapped. Make sure it's up-to-date */ 272003158cd7SNick Piggin if (!PageUptodate(page)) { 272103158cd7SNick Piggin err = mapping->a_ops->readpage(NULL, page); 272203158cd7SNick Piggin if (err) { 272303158cd7SNick Piggin page_cache_release(page); 272403158cd7SNick Piggin goto out; 272503158cd7SNick Piggin } 272603158cd7SNick Piggin lock_page(page); 272703158cd7SNick Piggin if (!PageUptodate(page)) { 272803158cd7SNick Piggin err = -EIO; 272903158cd7SNick Piggin goto unlock; 273003158cd7SNick Piggin } 273103158cd7SNick Piggin if (page_has_buffers(page)) 273203158cd7SNick Piggin goto has_buffers; 273303158cd7SNick Piggin } 2734eebd2aa3SChristoph Lameter zero_user(page, offset, length); 273503158cd7SNick Piggin set_page_dirty(page); 273603158cd7SNick Piggin err = 0; 273703158cd7SNick Piggin 273803158cd7SNick Piggin unlock: 27391da177e4SLinus Torvalds unlock_page(page); 27401da177e4SLinus Torvalds page_cache_release(page); 27411da177e4SLinus Torvalds out: 274203158cd7SNick Piggin return err; 27431da177e4SLinus Torvalds } 27441da177e4SLinus Torvalds EXPORT_SYMBOL(nobh_truncate_page); 27451da177e4SLinus Torvalds 27461da177e4SLinus Torvalds int block_truncate_page(struct address_space *mapping, 27471da177e4SLinus Torvalds loff_t from, get_block_t *get_block) 27481da177e4SLinus Torvalds { 27491da177e4SLinus Torvalds pgoff_t index = from >> PAGE_CACHE_SHIFT; 27501da177e4SLinus Torvalds unsigned offset = from & (PAGE_CACHE_SIZE-1); 27511da177e4SLinus Torvalds unsigned blocksize; 275254b21a79SAndrew Morton sector_t iblock; 27531da177e4SLinus Torvalds unsigned length, pos; 27541da177e4SLinus Torvalds struct inode *inode = mapping->host; 27551da177e4SLinus Torvalds struct page *page; 27561da177e4SLinus Torvalds struct buffer_head *bh; 27571da177e4SLinus Torvalds int err; 27581da177e4SLinus Torvalds 27591da177e4SLinus Torvalds blocksize = 1 << inode->i_blkbits; 27601da177e4SLinus Torvalds length = offset & (blocksize - 1); 27611da177e4SLinus Torvalds 27621da177e4SLinus Torvalds /* Block boundary? Nothing to do */ 27631da177e4SLinus Torvalds if (!length) 27641da177e4SLinus Torvalds return 0; 27651da177e4SLinus Torvalds 27661da177e4SLinus Torvalds length = blocksize - length; 276754b21a79SAndrew Morton iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 27681da177e4SLinus Torvalds 27691da177e4SLinus Torvalds page = grab_cache_page(mapping, index); 27701da177e4SLinus Torvalds err = -ENOMEM; 27711da177e4SLinus Torvalds if (!page) 27721da177e4SLinus Torvalds goto out; 27731da177e4SLinus Torvalds 27741da177e4SLinus Torvalds if (!page_has_buffers(page)) 27751da177e4SLinus Torvalds create_empty_buffers(page, blocksize, 0); 27761da177e4SLinus Torvalds 27771da177e4SLinus Torvalds /* Find the buffer that contains "offset" */ 27781da177e4SLinus Torvalds bh = page_buffers(page); 27791da177e4SLinus Torvalds pos = blocksize; 27801da177e4SLinus Torvalds while (offset >= pos) { 27811da177e4SLinus Torvalds bh = bh->b_this_page; 27821da177e4SLinus Torvalds iblock++; 27831da177e4SLinus Torvalds pos += blocksize; 27841da177e4SLinus Torvalds } 27851da177e4SLinus Torvalds 27861da177e4SLinus Torvalds err = 0; 27871da177e4SLinus Torvalds if (!buffer_mapped(bh)) { 2788b0cf2321SBadari Pulavarty WARN_ON(bh->b_size != blocksize); 27891da177e4SLinus Torvalds err = get_block(inode, iblock, bh, 0); 27901da177e4SLinus Torvalds if (err) 27911da177e4SLinus Torvalds goto unlock; 27921da177e4SLinus Torvalds /* unmapped? It's a hole - nothing to do */ 27931da177e4SLinus Torvalds if (!buffer_mapped(bh)) 27941da177e4SLinus Torvalds goto unlock; 27951da177e4SLinus Torvalds } 27961da177e4SLinus Torvalds 27971da177e4SLinus Torvalds /* Ok, it's mapped. Make sure it's up-to-date */ 27981da177e4SLinus Torvalds if (PageUptodate(page)) 27991da177e4SLinus Torvalds set_buffer_uptodate(bh); 28001da177e4SLinus Torvalds 280133a266ddSDavid Chinner if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { 28021da177e4SLinus Torvalds err = -EIO; 28031da177e4SLinus Torvalds ll_rw_block(READ, 1, &bh); 28041da177e4SLinus Torvalds wait_on_buffer(bh); 28051da177e4SLinus Torvalds /* Uhhuh. Read error. Complain and punt. */ 28061da177e4SLinus Torvalds if (!buffer_uptodate(bh)) 28071da177e4SLinus Torvalds goto unlock; 28081da177e4SLinus Torvalds } 28091da177e4SLinus Torvalds 2810eebd2aa3SChristoph Lameter zero_user(page, offset, length); 28111da177e4SLinus Torvalds mark_buffer_dirty(bh); 28121da177e4SLinus Torvalds err = 0; 28131da177e4SLinus Torvalds 28141da177e4SLinus Torvalds unlock: 28151da177e4SLinus Torvalds unlock_page(page); 28161da177e4SLinus Torvalds page_cache_release(page); 28171da177e4SLinus Torvalds out: 28181da177e4SLinus Torvalds return err; 28191da177e4SLinus Torvalds } 28201fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(block_truncate_page); 28211da177e4SLinus Torvalds 28221da177e4SLinus Torvalds /* 28231da177e4SLinus Torvalds * The generic ->writepage function for buffer-backed address_spaces 282435c80d5fSChris Mason * this form passes in the end_io handler used to finish the IO. 28251da177e4SLinus Torvalds */ 282635c80d5fSChris Mason int block_write_full_page_endio(struct page *page, get_block_t *get_block, 282735c80d5fSChris Mason struct writeback_control *wbc, bh_end_io_t *handler) 28281da177e4SLinus Torvalds { 28291da177e4SLinus Torvalds struct inode * const inode = page->mapping->host; 28301da177e4SLinus Torvalds loff_t i_size = i_size_read(inode); 28311da177e4SLinus Torvalds const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; 28321da177e4SLinus Torvalds unsigned offset; 28331da177e4SLinus Torvalds 28341da177e4SLinus Torvalds /* Is the page fully inside i_size? */ 28351da177e4SLinus Torvalds if (page->index < end_index) 283635c80d5fSChris Mason return __block_write_full_page(inode, page, get_block, wbc, 283735c80d5fSChris Mason handler); 28381da177e4SLinus Torvalds 28391da177e4SLinus Torvalds /* Is the page fully outside i_size? (truncate in progress) */ 28401da177e4SLinus Torvalds offset = i_size & (PAGE_CACHE_SIZE-1); 28411da177e4SLinus Torvalds if (page->index >= end_index+1 || !offset) { 28421da177e4SLinus Torvalds /* 28431da177e4SLinus Torvalds * The page may have dirty, unmapped buffers. For example, 28441da177e4SLinus Torvalds * they may have been added in ext3_writepage(). Make them 28451da177e4SLinus Torvalds * freeable here, so the page does not leak. 28461da177e4SLinus Torvalds */ 2847aaa4059bSJan Kara do_invalidatepage(page, 0); 28481da177e4SLinus Torvalds unlock_page(page); 28491da177e4SLinus Torvalds return 0; /* don't care */ 28501da177e4SLinus Torvalds } 28511da177e4SLinus Torvalds 28521da177e4SLinus Torvalds /* 28531da177e4SLinus Torvalds * The page straddles i_size. It must be zeroed out on each and every 28542a61aa40SAdam Buchbinder * writepage invocation because it may be mmapped. "A file is mapped 28551da177e4SLinus Torvalds * in multiples of the page size. For a file that is not a multiple of 28561da177e4SLinus Torvalds * the page size, the remaining memory is zeroed when mapped, and 28571da177e4SLinus Torvalds * writes to that region are not written out to the file." 28581da177e4SLinus Torvalds */ 2859eebd2aa3SChristoph Lameter zero_user_segment(page, offset, PAGE_CACHE_SIZE); 286035c80d5fSChris Mason return __block_write_full_page(inode, page, get_block, wbc, handler); 28611da177e4SLinus Torvalds } 28621fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(block_write_full_page_endio); 28631da177e4SLinus Torvalds 286435c80d5fSChris Mason /* 286535c80d5fSChris Mason * The generic ->writepage function for buffer-backed address_spaces 286635c80d5fSChris Mason */ 286735c80d5fSChris Mason int block_write_full_page(struct page *page, get_block_t *get_block, 286835c80d5fSChris Mason struct writeback_control *wbc) 286935c80d5fSChris Mason { 287035c80d5fSChris Mason return block_write_full_page_endio(page, get_block, wbc, 287135c80d5fSChris Mason end_buffer_async_write); 287235c80d5fSChris Mason } 28731fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(block_write_full_page); 287435c80d5fSChris Mason 28751da177e4SLinus Torvalds sector_t generic_block_bmap(struct address_space *mapping, sector_t block, 28761da177e4SLinus Torvalds get_block_t *get_block) 28771da177e4SLinus Torvalds { 28781da177e4SLinus Torvalds struct buffer_head tmp; 28791da177e4SLinus Torvalds struct inode *inode = mapping->host; 28801da177e4SLinus Torvalds tmp.b_state = 0; 28811da177e4SLinus Torvalds tmp.b_blocknr = 0; 2882b0cf2321SBadari Pulavarty tmp.b_size = 1 << inode->i_blkbits; 28831da177e4SLinus Torvalds get_block(inode, block, &tmp, 0); 28841da177e4SLinus Torvalds return tmp.b_blocknr; 28851da177e4SLinus Torvalds } 28861fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(generic_block_bmap); 28871da177e4SLinus Torvalds 28886712ecf8SNeilBrown static void end_bio_bh_io_sync(struct bio *bio, int err) 28891da177e4SLinus Torvalds { 28901da177e4SLinus Torvalds struct buffer_head *bh = bio->bi_private; 28911da177e4SLinus Torvalds 28921da177e4SLinus Torvalds if (err == -EOPNOTSUPP) { 28931da177e4SLinus Torvalds set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); 28941da177e4SLinus Torvalds set_bit(BH_Eopnotsupp, &bh->b_state); 28951da177e4SLinus Torvalds } 28961da177e4SLinus Torvalds 289708bafc03SKeith Mannthey if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) 289808bafc03SKeith Mannthey set_bit(BH_Quiet, &bh->b_state); 289908bafc03SKeith Mannthey 29001da177e4SLinus Torvalds bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); 29011da177e4SLinus Torvalds bio_put(bio); 29021da177e4SLinus Torvalds } 29031da177e4SLinus Torvalds 29041da177e4SLinus Torvalds int submit_bh(int rw, struct buffer_head * bh) 29051da177e4SLinus Torvalds { 29061da177e4SLinus Torvalds struct bio *bio; 29071da177e4SLinus Torvalds int ret = 0; 29081da177e4SLinus Torvalds 29091da177e4SLinus Torvalds BUG_ON(!buffer_locked(bh)); 29101da177e4SLinus Torvalds BUG_ON(!buffer_mapped(bh)); 29111da177e4SLinus Torvalds BUG_ON(!bh->b_end_io); 29128fb0e342SAneesh Kumar K.V BUG_ON(buffer_delay(bh)); 29138fb0e342SAneesh Kumar K.V BUG_ON(buffer_unwritten(bh)); 29141da177e4SLinus Torvalds 291548fd4f93SJens Axboe /* 291648fd4f93SJens Axboe * Only clear out a write error when rewriting 29171da177e4SLinus Torvalds */ 291848fd4f93SJens Axboe if (test_set_buffer_req(bh) && (rw & WRITE)) 29191da177e4SLinus Torvalds clear_buffer_write_io_error(bh); 29201da177e4SLinus Torvalds 29211da177e4SLinus Torvalds /* 29221da177e4SLinus Torvalds * from here on down, it's all bio -- do the initial mapping, 29231da177e4SLinus Torvalds * submit_bio -> generic_make_request may further map this bio around 29241da177e4SLinus Torvalds */ 29251da177e4SLinus Torvalds bio = bio_alloc(GFP_NOIO, 1); 29261da177e4SLinus Torvalds 29271da177e4SLinus Torvalds bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); 29281da177e4SLinus Torvalds bio->bi_bdev = bh->b_bdev; 29291da177e4SLinus Torvalds bio->bi_io_vec[0].bv_page = bh->b_page; 29301da177e4SLinus Torvalds bio->bi_io_vec[0].bv_len = bh->b_size; 29311da177e4SLinus Torvalds bio->bi_io_vec[0].bv_offset = bh_offset(bh); 29321da177e4SLinus Torvalds 29331da177e4SLinus Torvalds bio->bi_vcnt = 1; 29341da177e4SLinus Torvalds bio->bi_idx = 0; 29351da177e4SLinus Torvalds bio->bi_size = bh->b_size; 29361da177e4SLinus Torvalds 29371da177e4SLinus Torvalds bio->bi_end_io = end_bio_bh_io_sync; 29381da177e4SLinus Torvalds bio->bi_private = bh; 29391da177e4SLinus Torvalds 29401da177e4SLinus Torvalds bio_get(bio); 29411da177e4SLinus Torvalds submit_bio(rw, bio); 29421da177e4SLinus Torvalds 29431da177e4SLinus Torvalds if (bio_flagged(bio, BIO_EOPNOTSUPP)) 29441da177e4SLinus Torvalds ret = -EOPNOTSUPP; 29451da177e4SLinus Torvalds 29461da177e4SLinus Torvalds bio_put(bio); 29471da177e4SLinus Torvalds return ret; 29481da177e4SLinus Torvalds } 29491fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(submit_bh); 29501da177e4SLinus Torvalds 29511da177e4SLinus Torvalds /** 29521da177e4SLinus Torvalds * ll_rw_block: low-level access to block devices (DEPRECATED) 2953*9cb569d6SChristoph Hellwig * @rw: whether to %READ or %WRITE or maybe %READA (readahead) 29541da177e4SLinus Torvalds * @nr: number of &struct buffer_heads in the array 29551da177e4SLinus Torvalds * @bhs: array of pointers to &struct buffer_head 29561da177e4SLinus Torvalds * 2957a7662236SJan Kara * ll_rw_block() takes an array of pointers to &struct buffer_heads, and 2958a7662236SJan Kara * requests an I/O operation on them, either a %READ or a %WRITE. The third 2959*9cb569d6SChristoph Hellwig * %READA option is described in the documentation for generic_make_request() 2960*9cb569d6SChristoph Hellwig * which ll_rw_block() calls. 29611da177e4SLinus Torvalds * 29621da177e4SLinus Torvalds * This function drops any buffer that it cannot get a lock on (with the 2963*9cb569d6SChristoph Hellwig * BH_Lock state bit), any buffer that appears to be clean when doing a write 2964*9cb569d6SChristoph Hellwig * request, and any buffer that appears to be up-to-date when doing read 2965*9cb569d6SChristoph Hellwig * request. Further it marks as clean buffers that are processed for 2966*9cb569d6SChristoph Hellwig * writing (the buffer cache won't assume that they are actually clean 2967*9cb569d6SChristoph Hellwig * until the buffer gets unlocked). 29681da177e4SLinus Torvalds * 29691da177e4SLinus Torvalds * ll_rw_block sets b_end_io to simple completion handler that marks 29701da177e4SLinus Torvalds * the buffer up-to-date (if approriate), unlocks the buffer and wakes 29711da177e4SLinus Torvalds * any waiters. 29721da177e4SLinus Torvalds * 29731da177e4SLinus Torvalds * All of the buffers must be for the same device, and must also be a 29741da177e4SLinus Torvalds * multiple of the current approved size for the device. 29751da177e4SLinus Torvalds */ 29761da177e4SLinus Torvalds void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) 29771da177e4SLinus Torvalds { 29781da177e4SLinus Torvalds int i; 29791da177e4SLinus Torvalds 29801da177e4SLinus Torvalds for (i = 0; i < nr; i++) { 29811da177e4SLinus Torvalds struct buffer_head *bh = bhs[i]; 29821da177e4SLinus Torvalds 2983*9cb569d6SChristoph Hellwig if (!trylock_buffer(bh)) 29841da177e4SLinus Torvalds continue; 2985*9cb569d6SChristoph Hellwig if (rw == WRITE) { 29861da177e4SLinus Torvalds if (test_clear_buffer_dirty(bh)) { 298776c3073aSakpm@osdl.org bh->b_end_io = end_buffer_write_sync; 2988e60e5c50SOGAWA Hirofumi get_bh(bh); 29891da177e4SLinus Torvalds submit_bh(WRITE, bh); 29901da177e4SLinus Torvalds continue; 29911da177e4SLinus Torvalds } 29921da177e4SLinus Torvalds } else { 29931da177e4SLinus Torvalds if (!buffer_uptodate(bh)) { 299476c3073aSakpm@osdl.org bh->b_end_io = end_buffer_read_sync; 2995e60e5c50SOGAWA Hirofumi get_bh(bh); 29961da177e4SLinus Torvalds submit_bh(rw, bh); 29971da177e4SLinus Torvalds continue; 29981da177e4SLinus Torvalds } 29991da177e4SLinus Torvalds } 30001da177e4SLinus Torvalds unlock_buffer(bh); 30011da177e4SLinus Torvalds } 30021da177e4SLinus Torvalds } 30031fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(ll_rw_block); 30041da177e4SLinus Torvalds 3005*9cb569d6SChristoph Hellwig void write_dirty_buffer(struct buffer_head *bh, int rw) 3006*9cb569d6SChristoph Hellwig { 3007*9cb569d6SChristoph Hellwig lock_buffer(bh); 3008*9cb569d6SChristoph Hellwig if (!test_clear_buffer_dirty(bh)) { 3009*9cb569d6SChristoph Hellwig unlock_buffer(bh); 3010*9cb569d6SChristoph Hellwig return; 3011*9cb569d6SChristoph Hellwig } 3012*9cb569d6SChristoph Hellwig bh->b_end_io = end_buffer_write_sync; 3013*9cb569d6SChristoph Hellwig get_bh(bh); 3014*9cb569d6SChristoph Hellwig submit_bh(rw, bh); 3015*9cb569d6SChristoph Hellwig } 3016*9cb569d6SChristoph Hellwig EXPORT_SYMBOL(write_dirty_buffer); 3017*9cb569d6SChristoph Hellwig 30181da177e4SLinus Torvalds /* 30191da177e4SLinus Torvalds * For a data-integrity writeout, we need to wait upon any in-progress I/O 30201da177e4SLinus Torvalds * and then start new I/O and then wait upon it. The caller must have a ref on 30211da177e4SLinus Torvalds * the buffer_head. 30221da177e4SLinus Torvalds */ 302387e99511SChristoph Hellwig int __sync_dirty_buffer(struct buffer_head *bh, int rw) 30241da177e4SLinus Torvalds { 30251da177e4SLinus Torvalds int ret = 0; 30261da177e4SLinus Torvalds 30271da177e4SLinus Torvalds WARN_ON(atomic_read(&bh->b_count) < 1); 30281da177e4SLinus Torvalds lock_buffer(bh); 30291da177e4SLinus Torvalds if (test_clear_buffer_dirty(bh)) { 30301da177e4SLinus Torvalds get_bh(bh); 30311da177e4SLinus Torvalds bh->b_end_io = end_buffer_write_sync; 303287e99511SChristoph Hellwig ret = submit_bh(rw, bh); 30331da177e4SLinus Torvalds wait_on_buffer(bh); 30341da177e4SLinus Torvalds if (buffer_eopnotsupp(bh)) { 30351da177e4SLinus Torvalds clear_buffer_eopnotsupp(bh); 30361da177e4SLinus Torvalds ret = -EOPNOTSUPP; 30371da177e4SLinus Torvalds } 30381da177e4SLinus Torvalds if (!ret && !buffer_uptodate(bh)) 30391da177e4SLinus Torvalds ret = -EIO; 30401da177e4SLinus Torvalds } else { 30411da177e4SLinus Torvalds unlock_buffer(bh); 30421da177e4SLinus Torvalds } 30431da177e4SLinus Torvalds return ret; 30441da177e4SLinus Torvalds } 304587e99511SChristoph Hellwig EXPORT_SYMBOL(__sync_dirty_buffer); 304687e99511SChristoph Hellwig 304787e99511SChristoph Hellwig int sync_dirty_buffer(struct buffer_head *bh) 304887e99511SChristoph Hellwig { 304987e99511SChristoph Hellwig return __sync_dirty_buffer(bh, WRITE_SYNC); 305087e99511SChristoph Hellwig } 30511fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(sync_dirty_buffer); 30521da177e4SLinus Torvalds 30531da177e4SLinus Torvalds /* 30541da177e4SLinus Torvalds * try_to_free_buffers() checks if all the buffers on this particular page 30551da177e4SLinus Torvalds * are unused, and releases them if so. 30561da177e4SLinus Torvalds * 30571da177e4SLinus Torvalds * Exclusion against try_to_free_buffers may be obtained by either 30581da177e4SLinus Torvalds * locking the page or by holding its mapping's private_lock. 30591da177e4SLinus Torvalds * 30601da177e4SLinus Torvalds * If the page is dirty but all the buffers are clean then we need to 30611da177e4SLinus Torvalds * be sure to mark the page clean as well. This is because the page 30621da177e4SLinus Torvalds * may be against a block device, and a later reattachment of buffers 30631da177e4SLinus Torvalds * to a dirty page will set *all* buffers dirty. Which would corrupt 30641da177e4SLinus Torvalds * filesystem data on the same device. 30651da177e4SLinus Torvalds * 30661da177e4SLinus Torvalds * The same applies to regular filesystem pages: if all the buffers are 30671da177e4SLinus Torvalds * clean then we set the page clean and proceed. To do that, we require 30681da177e4SLinus Torvalds * total exclusion from __set_page_dirty_buffers(). That is obtained with 30691da177e4SLinus Torvalds * private_lock. 30701da177e4SLinus Torvalds * 30711da177e4SLinus Torvalds * try_to_free_buffers() is non-blocking. 30721da177e4SLinus Torvalds */ 30731da177e4SLinus Torvalds static inline int buffer_busy(struct buffer_head *bh) 30741da177e4SLinus Torvalds { 30751da177e4SLinus Torvalds return atomic_read(&bh->b_count) | 30761da177e4SLinus Torvalds (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); 30771da177e4SLinus Torvalds } 30781da177e4SLinus Torvalds 30791da177e4SLinus Torvalds static int 30801da177e4SLinus Torvalds drop_buffers(struct page *page, struct buffer_head **buffers_to_free) 30811da177e4SLinus Torvalds { 30821da177e4SLinus Torvalds struct buffer_head *head = page_buffers(page); 30831da177e4SLinus Torvalds struct buffer_head *bh; 30841da177e4SLinus Torvalds 30851da177e4SLinus Torvalds bh = head; 30861da177e4SLinus Torvalds do { 3087de7d5a3bSakpm@osdl.org if (buffer_write_io_error(bh) && page->mapping) 30881da177e4SLinus Torvalds set_bit(AS_EIO, &page->mapping->flags); 30891da177e4SLinus Torvalds if (buffer_busy(bh)) 30901da177e4SLinus Torvalds goto failed; 30911da177e4SLinus Torvalds bh = bh->b_this_page; 30921da177e4SLinus Torvalds } while (bh != head); 30931da177e4SLinus Torvalds 30941da177e4SLinus Torvalds do { 30951da177e4SLinus Torvalds struct buffer_head *next = bh->b_this_page; 30961da177e4SLinus Torvalds 3097535ee2fbSJan Kara if (bh->b_assoc_map) 30981da177e4SLinus Torvalds __remove_assoc_queue(bh); 30991da177e4SLinus Torvalds bh = next; 31001da177e4SLinus Torvalds } while (bh != head); 31011da177e4SLinus Torvalds *buffers_to_free = head; 31021da177e4SLinus Torvalds __clear_page_buffers(page); 31031da177e4SLinus Torvalds return 1; 31041da177e4SLinus Torvalds failed: 31051da177e4SLinus Torvalds return 0; 31061da177e4SLinus Torvalds } 31071da177e4SLinus Torvalds 31081da177e4SLinus Torvalds int try_to_free_buffers(struct page *page) 31091da177e4SLinus Torvalds { 31101da177e4SLinus Torvalds struct address_space * const mapping = page->mapping; 31111da177e4SLinus Torvalds struct buffer_head *buffers_to_free = NULL; 31121da177e4SLinus Torvalds int ret = 0; 31131da177e4SLinus Torvalds 31141da177e4SLinus Torvalds BUG_ON(!PageLocked(page)); 3115ecdfc978SLinus Torvalds if (PageWriteback(page)) 31161da177e4SLinus Torvalds return 0; 31171da177e4SLinus Torvalds 31181da177e4SLinus Torvalds if (mapping == NULL) { /* can this still happen? */ 31191da177e4SLinus Torvalds ret = drop_buffers(page, &buffers_to_free); 31201da177e4SLinus Torvalds goto out; 31211da177e4SLinus Torvalds } 31221da177e4SLinus Torvalds 31231da177e4SLinus Torvalds spin_lock(&mapping->private_lock); 31241da177e4SLinus Torvalds ret = drop_buffers(page, &buffers_to_free); 3125ecdfc978SLinus Torvalds 3126ecdfc978SLinus Torvalds /* 3127ecdfc978SLinus Torvalds * If the filesystem writes its buffers by hand (eg ext3) 3128ecdfc978SLinus Torvalds * then we can have clean buffers against a dirty page. We 3129ecdfc978SLinus Torvalds * clean the page here; otherwise the VM will never notice 3130ecdfc978SLinus Torvalds * that the filesystem did any IO at all. 3131ecdfc978SLinus Torvalds * 3132ecdfc978SLinus Torvalds * Also, during truncate, discard_buffer will have marked all 3133ecdfc978SLinus Torvalds * the page's buffers clean. We discover that here and clean 3134ecdfc978SLinus Torvalds * the page also. 313587df7241SNick Piggin * 313687df7241SNick Piggin * private_lock must be held over this entire operation in order 313787df7241SNick Piggin * to synchronise against __set_page_dirty_buffers and prevent the 313887df7241SNick Piggin * dirty bit from being lost. 3139ecdfc978SLinus Torvalds */ 3140ecdfc978SLinus Torvalds if (ret) 3141ecdfc978SLinus Torvalds cancel_dirty_page(page, PAGE_CACHE_SIZE); 314287df7241SNick Piggin spin_unlock(&mapping->private_lock); 31431da177e4SLinus Torvalds out: 31441da177e4SLinus Torvalds if (buffers_to_free) { 31451da177e4SLinus Torvalds struct buffer_head *bh = buffers_to_free; 31461da177e4SLinus Torvalds 31471da177e4SLinus Torvalds do { 31481da177e4SLinus Torvalds struct buffer_head *next = bh->b_this_page; 31491da177e4SLinus Torvalds free_buffer_head(bh); 31501da177e4SLinus Torvalds bh = next; 31511da177e4SLinus Torvalds } while (bh != buffers_to_free); 31521da177e4SLinus Torvalds } 31531da177e4SLinus Torvalds return ret; 31541da177e4SLinus Torvalds } 31551da177e4SLinus Torvalds EXPORT_SYMBOL(try_to_free_buffers); 31561da177e4SLinus Torvalds 31573978d717SNeilBrown void block_sync_page(struct page *page) 31581da177e4SLinus Torvalds { 31591da177e4SLinus Torvalds struct address_space *mapping; 31601da177e4SLinus Torvalds 31611da177e4SLinus Torvalds smp_mb(); 31621da177e4SLinus Torvalds mapping = page_mapping(page); 31631da177e4SLinus Torvalds if (mapping) 31641da177e4SLinus Torvalds blk_run_backing_dev(mapping->backing_dev_info, page); 31651da177e4SLinus Torvalds } 31661fe72eaaSH Hartley Sweeten EXPORT_SYMBOL(block_sync_page); 31671da177e4SLinus Torvalds 31681da177e4SLinus Torvalds /* 31691da177e4SLinus Torvalds * There are no bdflush tunables left. But distributions are 31701da177e4SLinus Torvalds * still running obsolete flush daemons, so we terminate them here. 31711da177e4SLinus Torvalds * 31721da177e4SLinus Torvalds * Use of bdflush() is deprecated and will be removed in a future kernel. 31735b0830cbSJens Axboe * The `flush-X' kernel threads fully replace bdflush daemons and this call. 31741da177e4SLinus Torvalds */ 3175bdc480e3SHeiko Carstens SYSCALL_DEFINE2(bdflush, int, func, long, data) 31761da177e4SLinus Torvalds { 31771da177e4SLinus Torvalds static int msg_count; 31781da177e4SLinus Torvalds 31791da177e4SLinus Torvalds if (!capable(CAP_SYS_ADMIN)) 31801da177e4SLinus Torvalds return -EPERM; 31811da177e4SLinus Torvalds 31821da177e4SLinus Torvalds if (msg_count < 5) { 31831da177e4SLinus Torvalds msg_count++; 31841da177e4SLinus Torvalds printk(KERN_INFO 31851da177e4SLinus Torvalds "warning: process `%s' used the obsolete bdflush" 31861da177e4SLinus Torvalds " system call\n", current->comm); 31871da177e4SLinus Torvalds printk(KERN_INFO "Fix your initscripts?\n"); 31881da177e4SLinus Torvalds } 31891da177e4SLinus Torvalds 31901da177e4SLinus Torvalds if (func == 1) 31911da177e4SLinus Torvalds do_exit(0); 31921da177e4SLinus Torvalds return 0; 31931da177e4SLinus Torvalds } 31941da177e4SLinus Torvalds 31951da177e4SLinus Torvalds /* 31961da177e4SLinus Torvalds * Buffer-head allocation 31971da177e4SLinus Torvalds */ 3198e18b890bSChristoph Lameter static struct kmem_cache *bh_cachep; 31991da177e4SLinus Torvalds 32001da177e4SLinus Torvalds /* 32011da177e4SLinus Torvalds * Once the number of bh's in the machine exceeds this level, we start 32021da177e4SLinus Torvalds * stripping them in writeback. 32031da177e4SLinus Torvalds */ 32041da177e4SLinus Torvalds static int max_buffer_heads; 32051da177e4SLinus Torvalds 32061da177e4SLinus Torvalds int buffer_heads_over_limit; 32071da177e4SLinus Torvalds 32081da177e4SLinus Torvalds struct bh_accounting { 32091da177e4SLinus Torvalds int nr; /* Number of live bh's */ 32101da177e4SLinus Torvalds int ratelimit; /* Limit cacheline bouncing */ 32111da177e4SLinus Torvalds }; 32121da177e4SLinus Torvalds 32131da177e4SLinus Torvalds static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; 32141da177e4SLinus Torvalds 32151da177e4SLinus Torvalds static void recalc_bh_state(void) 32161da177e4SLinus Torvalds { 32171da177e4SLinus Torvalds int i; 32181da177e4SLinus Torvalds int tot = 0; 32191da177e4SLinus Torvalds 32201da177e4SLinus Torvalds if (__get_cpu_var(bh_accounting).ratelimit++ < 4096) 32211da177e4SLinus Torvalds return; 32221da177e4SLinus Torvalds __get_cpu_var(bh_accounting).ratelimit = 0; 32238a143426SEric Dumazet for_each_online_cpu(i) 32241da177e4SLinus Torvalds tot += per_cpu(bh_accounting, i).nr; 32251da177e4SLinus Torvalds buffer_heads_over_limit = (tot > max_buffer_heads); 32261da177e4SLinus Torvalds } 32271da177e4SLinus Torvalds 3228dd0fc66fSAl Viro struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) 32291da177e4SLinus Torvalds { 3230019b4d12SRichard Kennedy struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); 32311da177e4SLinus Torvalds if (ret) { 3232a35afb83SChristoph Lameter INIT_LIST_HEAD(&ret->b_assoc_buffers); 3233736c7b80SCoywolf Qi Hunt get_cpu_var(bh_accounting).nr++; 32341da177e4SLinus Torvalds recalc_bh_state(); 3235736c7b80SCoywolf Qi Hunt put_cpu_var(bh_accounting); 32361da177e4SLinus Torvalds } 32371da177e4SLinus Torvalds return ret; 32381da177e4SLinus Torvalds } 32391da177e4SLinus Torvalds EXPORT_SYMBOL(alloc_buffer_head); 32401da177e4SLinus Torvalds 32411da177e4SLinus Torvalds void free_buffer_head(struct buffer_head *bh) 32421da177e4SLinus Torvalds { 32431da177e4SLinus Torvalds BUG_ON(!list_empty(&bh->b_assoc_buffers)); 32441da177e4SLinus Torvalds kmem_cache_free(bh_cachep, bh); 3245736c7b80SCoywolf Qi Hunt get_cpu_var(bh_accounting).nr--; 32461da177e4SLinus Torvalds recalc_bh_state(); 3247736c7b80SCoywolf Qi Hunt put_cpu_var(bh_accounting); 32481da177e4SLinus Torvalds } 32491da177e4SLinus Torvalds EXPORT_SYMBOL(free_buffer_head); 32501da177e4SLinus Torvalds 32511da177e4SLinus Torvalds static void buffer_exit_cpu(int cpu) 32521da177e4SLinus Torvalds { 32531da177e4SLinus Torvalds int i; 32541da177e4SLinus Torvalds struct bh_lru *b = &per_cpu(bh_lrus, cpu); 32551da177e4SLinus Torvalds 32561da177e4SLinus Torvalds for (i = 0; i < BH_LRU_SIZE; i++) { 32571da177e4SLinus Torvalds brelse(b->bhs[i]); 32581da177e4SLinus Torvalds b->bhs[i] = NULL; 32591da177e4SLinus Torvalds } 32608a143426SEric Dumazet get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr; 32618a143426SEric Dumazet per_cpu(bh_accounting, cpu).nr = 0; 32628a143426SEric Dumazet put_cpu_var(bh_accounting); 32631da177e4SLinus Torvalds } 32641da177e4SLinus Torvalds 32651da177e4SLinus Torvalds static int buffer_cpu_notify(struct notifier_block *self, 32661da177e4SLinus Torvalds unsigned long action, void *hcpu) 32671da177e4SLinus Torvalds { 32688bb78442SRafael J. Wysocki if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) 32691da177e4SLinus Torvalds buffer_exit_cpu((unsigned long)hcpu); 32701da177e4SLinus Torvalds return NOTIFY_OK; 32711da177e4SLinus Torvalds } 32721da177e4SLinus Torvalds 3273389d1b08SAneesh Kumar K.V /** 3274a6b91919SRandy Dunlap * bh_uptodate_or_lock - Test whether the buffer is uptodate 3275389d1b08SAneesh Kumar K.V * @bh: struct buffer_head 3276389d1b08SAneesh Kumar K.V * 3277389d1b08SAneesh Kumar K.V * Return true if the buffer is up-to-date and false, 3278389d1b08SAneesh Kumar K.V * with the buffer locked, if not. 3279389d1b08SAneesh Kumar K.V */ 3280389d1b08SAneesh Kumar K.V int bh_uptodate_or_lock(struct buffer_head *bh) 3281389d1b08SAneesh Kumar K.V { 3282389d1b08SAneesh Kumar K.V if (!buffer_uptodate(bh)) { 3283389d1b08SAneesh Kumar K.V lock_buffer(bh); 3284389d1b08SAneesh Kumar K.V if (!buffer_uptodate(bh)) 3285389d1b08SAneesh Kumar K.V return 0; 3286389d1b08SAneesh Kumar K.V unlock_buffer(bh); 3287389d1b08SAneesh Kumar K.V } 3288389d1b08SAneesh Kumar K.V return 1; 3289389d1b08SAneesh Kumar K.V } 3290389d1b08SAneesh Kumar K.V EXPORT_SYMBOL(bh_uptodate_or_lock); 3291389d1b08SAneesh Kumar K.V 3292389d1b08SAneesh Kumar K.V /** 3293a6b91919SRandy Dunlap * bh_submit_read - Submit a locked buffer for reading 3294389d1b08SAneesh Kumar K.V * @bh: struct buffer_head 3295389d1b08SAneesh Kumar K.V * 3296389d1b08SAneesh Kumar K.V * Returns zero on success and -EIO on error. 3297389d1b08SAneesh Kumar K.V */ 3298389d1b08SAneesh Kumar K.V int bh_submit_read(struct buffer_head *bh) 3299389d1b08SAneesh Kumar K.V { 3300389d1b08SAneesh Kumar K.V BUG_ON(!buffer_locked(bh)); 3301389d1b08SAneesh Kumar K.V 3302389d1b08SAneesh Kumar K.V if (buffer_uptodate(bh)) { 3303389d1b08SAneesh Kumar K.V unlock_buffer(bh); 3304389d1b08SAneesh Kumar K.V return 0; 3305389d1b08SAneesh Kumar K.V } 3306389d1b08SAneesh Kumar K.V 3307389d1b08SAneesh Kumar K.V get_bh(bh); 3308389d1b08SAneesh Kumar K.V bh->b_end_io = end_buffer_read_sync; 3309389d1b08SAneesh Kumar K.V submit_bh(READ, bh); 3310389d1b08SAneesh Kumar K.V wait_on_buffer(bh); 3311389d1b08SAneesh Kumar K.V if (buffer_uptodate(bh)) 3312389d1b08SAneesh Kumar K.V return 0; 3313389d1b08SAneesh Kumar K.V return -EIO; 3314389d1b08SAneesh Kumar K.V } 3315389d1b08SAneesh Kumar K.V EXPORT_SYMBOL(bh_submit_read); 3316389d1b08SAneesh Kumar K.V 33171da177e4SLinus Torvalds void __init buffer_init(void) 33181da177e4SLinus Torvalds { 33191da177e4SLinus Torvalds int nrpages; 33201da177e4SLinus Torvalds 3321b98938c3SChristoph Lameter bh_cachep = kmem_cache_create("buffer_head", 3322b98938c3SChristoph Lameter sizeof(struct buffer_head), 0, 3323b98938c3SChristoph Lameter (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| 3324b98938c3SChristoph Lameter SLAB_MEM_SPREAD), 3325019b4d12SRichard Kennedy NULL); 33261da177e4SLinus Torvalds 33271da177e4SLinus Torvalds /* 33281da177e4SLinus Torvalds * Limit the bh occupancy to 10% of ZONE_NORMAL 33291da177e4SLinus Torvalds */ 33301da177e4SLinus Torvalds nrpages = (nr_free_buffer_pages() * 10) / 100; 33311da177e4SLinus Torvalds max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); 33321da177e4SLinus Torvalds hotcpu_notifier(buffer_cpu_notify, 0); 33331da177e4SLinus Torvalds } 3334