1 /* 2 * Copyright (c) 2013 3 * Phillip Lougher <phillip@squashfs.org.uk> 4 * 5 * This work is licensed under the terms of the GNU GPL, version 2. See 6 * the COPYING file in the top-level directory. 7 */ 8 9 #include <linux/fs.h> 10 #include <linux/vfs.h> 11 #include <linux/kernel.h> 12 #include <linux/slab.h> 13 #include <linux/string.h> 14 #include <linux/pagemap.h> 15 #include <linux/mutex.h> 16 17 #include "squashfs_fs.h" 18 #include "squashfs_fs_sb.h" 19 #include "squashfs_fs_i.h" 20 #include "squashfs.h" 21 #include "page_actor.h" 22 23 static int squashfs_read_cache(struct page *target_page, u64 block, int bsize, 24 int pages, struct page **page); 25 26 /* Read separately compressed datablock directly into page cache */ 27 int squashfs_readpage_block(struct page *target_page, u64 block, int bsize) 28 29 { 30 struct inode *inode = target_page->mapping->host; 31 struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; 32 33 int file_end = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT; 34 int mask = (1 << (msblk->block_log - PAGE_CACHE_SHIFT)) - 1; 35 int start_index = target_page->index & ~mask; 36 int end_index = start_index | mask; 37 int i, n, pages, missing_pages, bytes, res = -ENOMEM; 38 struct page **page; 39 struct squashfs_page_actor *actor; 40 void *pageaddr; 41 42 if (end_index > file_end) 43 end_index = file_end; 44 45 pages = end_index - start_index + 1; 46 47 page = kmalloc(sizeof(void *) * pages, GFP_KERNEL); 48 if (page == NULL) 49 return res; 50 51 /* 52 * Create a "page actor" which will kmap and kunmap the 53 * page cache pages appropriately within the decompressor 54 */ 55 actor = squashfs_page_actor_init_special(page, pages, 0); 56 if (actor == NULL) 57 goto out; 58 59 /* Try to grab all the pages covered by the Squashfs block */ 60 for (missing_pages = 0, i = 0, n = start_index; i < pages; i++, n++) { 61 page[i] = (n == target_page->index) ? target_page : 62 grab_cache_page_nowait(target_page->mapping, n); 63 64 if (page[i] == NULL) { 65 missing_pages++; 66 continue; 67 } 68 69 if (PageUptodate(page[i])) { 70 unlock_page(page[i]); 71 page_cache_release(page[i]); 72 page[i] = NULL; 73 missing_pages++; 74 } 75 } 76 77 if (missing_pages) { 78 /* 79 * Couldn't get one or more pages, this page has either 80 * been VM reclaimed, but others are still in the page cache 81 * and uptodate, or we're racing with another thread in 82 * squashfs_readpage also trying to grab them. Fall back to 83 * using an intermediate buffer. 84 */ 85 res = squashfs_read_cache(target_page, block, bsize, pages, 86 page); 87 goto out; 88 } 89 90 /* Decompress directly into the page cache buffers */ 91 res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor); 92 if (res < 0) 93 goto mark_errored; 94 95 /* Last page may have trailing bytes not filled */ 96 bytes = res % PAGE_CACHE_SIZE; 97 if (bytes) { 98 pageaddr = kmap_atomic(page[pages - 1]); 99 memset(pageaddr + bytes, 0, PAGE_CACHE_SIZE - bytes); 100 kunmap_atomic(pageaddr); 101 } 102 103 /* Mark pages as uptodate, unlock and release */ 104 for (i = 0; i < pages; i++) { 105 flush_dcache_page(page[i]); 106 SetPageUptodate(page[i]); 107 unlock_page(page[i]); 108 if (page[i] != target_page) 109 page_cache_release(page[i]); 110 } 111 112 kfree(actor); 113 kfree(page); 114 115 return 0; 116 117 mark_errored: 118 /* Decompression failed, mark pages as errored. Target_page is 119 * dealt with by the caller 120 */ 121 for (i = 0; i < pages; i++) { 122 if (page[i] == target_page) 123 continue; 124 flush_dcache_page(page[i]); 125 SetPageError(page[i]); 126 unlock_page(page[i]); 127 page_cache_release(page[i]); 128 } 129 130 out: 131 kfree(actor); 132 kfree(page); 133 return res; 134 } 135 136 137 static int squashfs_read_cache(struct page *target_page, u64 block, int bsize, 138 int pages, struct page **page) 139 { 140 struct inode *i = target_page->mapping->host; 141 struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb, 142 block, bsize); 143 int bytes = buffer->length, res = buffer->error, n, offset = 0; 144 void *pageaddr; 145 146 if (res) { 147 ERROR("Unable to read page, block %llx, size %x\n", block, 148 bsize); 149 goto out; 150 } 151 152 for (n = 0; n < pages && bytes > 0; n++, 153 bytes -= PAGE_CACHE_SIZE, offset += PAGE_CACHE_SIZE) { 154 int avail = min_t(int, bytes, PAGE_CACHE_SIZE); 155 156 if (page[n] == NULL) 157 continue; 158 159 pageaddr = kmap_atomic(page[n]); 160 squashfs_copy_data(pageaddr, buffer, offset, avail); 161 memset(pageaddr + avail, 0, PAGE_CACHE_SIZE - avail); 162 kunmap_atomic(pageaddr); 163 flush_dcache_page(page[n]); 164 SetPageUptodate(page[n]); 165 unlock_page(page[n]); 166 if (page[n] != target_page) 167 page_cache_release(page[n]); 168 } 169 170 out: 171 squashfs_cache_put(buffer); 172 return res; 173 } 174