1 /* 2 * High-level sync()-related operations 3 */ 4 5 #include <linux/kernel.h> 6 #include <linux/file.h> 7 #include <linux/fs.h> 8 #include <linux/slab.h> 9 #include <linux/module.h> 10 #include <linux/sched.h> 11 #include <linux/writeback.h> 12 #include <linux/syscalls.h> 13 #include <linux/linkage.h> 14 #include <linux/pagemap.h> 15 #include <linux/quotaops.h> 16 #include <linux/buffer_head.h> 17 #include "internal.h" 18 19 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \ 20 SYNC_FILE_RANGE_WAIT_AFTER) 21 22 /* 23 * Do the filesystem syncing work. For simple filesystems 24 * writeback_inodes_sb(sb) just dirties buffers with inodes so we have to 25 * submit IO for these buffers via __sync_blockdev(). This also speeds up the 26 * wait == 1 case since in that case write_inode() functions do 27 * sync_dirty_buffer() and thus effectively write one block at a time. 28 */ 29 static int __sync_filesystem(struct super_block *sb, int wait) 30 { 31 /* 32 * This should be safe, as we require bdi backing to actually 33 * write out data in the first place 34 */ 35 if (!sb->s_bdi) 36 return 0; 37 38 if (sb->s_qcop && sb->s_qcop->quota_sync) 39 sb->s_qcop->quota_sync(sb, -1, wait); 40 41 if (wait) 42 sync_inodes_sb(sb); 43 else 44 writeback_inodes_sb(sb); 45 46 if (sb->s_op->sync_fs) 47 sb->s_op->sync_fs(sb, wait); 48 return __sync_blockdev(sb->s_bdev, wait); 49 } 50 51 /* 52 * Write out and wait upon all dirty data associated with this 53 * superblock. Filesystem data as well as the underlying block 54 * device. Takes the superblock lock. 55 */ 56 int sync_filesystem(struct super_block *sb) 57 { 58 int ret; 59 60 /* 61 * We need to be protected against the filesystem going from 62 * r/o to r/w or vice versa. 63 */ 64 WARN_ON(!rwsem_is_locked(&sb->s_umount)); 65 66 /* 67 * No point in syncing out anything if the filesystem is read-only. 68 */ 69 if (sb->s_flags & MS_RDONLY) 70 return 0; 71 72 ret = __sync_filesystem(sb, 0); 73 if (ret < 0) 74 return ret; 75 return __sync_filesystem(sb, 1); 76 } 77 EXPORT_SYMBOL_GPL(sync_filesystem); 78 79 /* 80 * Sync all the data for all the filesystems (called by sys_sync() and 81 * emergency sync) 82 * 83 * This operation is careful to avoid the livelock which could easily happen 84 * if two or more filesystems are being continuously dirtied. s_need_sync 85 * is used only here. We set it against all filesystems and then clear it as 86 * we sync them. So redirtied filesystems are skipped. 87 * 88 * But if process A is currently running sync_filesystems and then process B 89 * calls sync_filesystems as well, process B will set all the s_need_sync 90 * flags again, which will cause process A to resync everything. Fix that with 91 * a local mutex. 92 */ 93 static void sync_filesystems(int wait) 94 { 95 struct super_block *sb; 96 static DEFINE_MUTEX(mutex); 97 98 mutex_lock(&mutex); /* Could be down_interruptible */ 99 spin_lock(&sb_lock); 100 list_for_each_entry(sb, &super_blocks, s_list) 101 sb->s_need_sync = 1; 102 103 restart: 104 list_for_each_entry(sb, &super_blocks, s_list) { 105 if (!sb->s_need_sync) 106 continue; 107 sb->s_need_sync = 0; 108 sb->s_count++; 109 spin_unlock(&sb_lock); 110 111 down_read(&sb->s_umount); 112 if (!(sb->s_flags & MS_RDONLY) && sb->s_root && sb->s_bdi) 113 __sync_filesystem(sb, wait); 114 up_read(&sb->s_umount); 115 116 /* restart only when sb is no longer on the list */ 117 spin_lock(&sb_lock); 118 if (__put_super_and_need_restart(sb)) 119 goto restart; 120 } 121 spin_unlock(&sb_lock); 122 mutex_unlock(&mutex); 123 } 124 125 /* 126 * sync everything. Start out by waking pdflush, because that writes back 127 * all queues in parallel. 128 */ 129 SYSCALL_DEFINE0(sync) 130 { 131 wakeup_flusher_threads(0); 132 sync_filesystems(0); 133 sync_filesystems(1); 134 if (unlikely(laptop_mode)) 135 laptop_sync_completion(); 136 return 0; 137 } 138 139 static void do_sync_work(struct work_struct *work) 140 { 141 /* 142 * Sync twice to reduce the possibility we skipped some inodes / pages 143 * because they were temporarily locked 144 */ 145 sync_filesystems(0); 146 sync_filesystems(0); 147 printk("Emergency Sync complete\n"); 148 kfree(work); 149 } 150 151 void emergency_sync(void) 152 { 153 struct work_struct *work; 154 155 work = kmalloc(sizeof(*work), GFP_ATOMIC); 156 if (work) { 157 INIT_WORK(work, do_sync_work); 158 schedule_work(work); 159 } 160 } 161 162 /* 163 * Generic function to fsync a file. 164 * 165 * filp may be NULL if called via the msync of a vma. 166 */ 167 int file_fsync(struct file *filp, struct dentry *dentry, int datasync) 168 { 169 struct inode * inode = dentry->d_inode; 170 struct super_block * sb; 171 int ret, err; 172 173 /* sync the inode to buffers */ 174 ret = write_inode_now(inode, 0); 175 176 /* sync the superblock to buffers */ 177 sb = inode->i_sb; 178 if (sb->s_dirt && sb->s_op->write_super) 179 sb->s_op->write_super(sb); 180 181 /* .. finally sync the buffers to disk */ 182 err = sync_blockdev(sb->s_bdev); 183 if (!ret) 184 ret = err; 185 return ret; 186 } 187 EXPORT_SYMBOL(file_fsync); 188 189 /** 190 * vfs_fsync_range - helper to sync a range of data & metadata to disk 191 * @file: file to sync 192 * @dentry: dentry of @file 193 * @start: offset in bytes of the beginning of data range to sync 194 * @end: offset in bytes of the end of data range (inclusive) 195 * @datasync: perform only datasync 196 * 197 * Write back data in range @start..@end and metadata for @file to disk. If 198 * @datasync is set only metadata needed to access modified file data is 199 * written. 200 * 201 * In case this function is called from nfsd @file may be %NULL and 202 * only @dentry is set. This can only happen when the filesystem 203 * implements the export_operations API. 204 */ 205 int vfs_fsync_range(struct file *file, struct dentry *dentry, loff_t start, 206 loff_t end, int datasync) 207 { 208 const struct file_operations *fop; 209 struct address_space *mapping; 210 int err, ret; 211 212 /* 213 * Get mapping and operations from the file in case we have 214 * as file, or get the default values for them in case we 215 * don't have a struct file available. Damn nfsd.. 216 */ 217 if (file) { 218 mapping = file->f_mapping; 219 fop = file->f_op; 220 } else { 221 mapping = dentry->d_inode->i_mapping; 222 fop = dentry->d_inode->i_fop; 223 } 224 225 if (!fop || !fop->fsync) { 226 ret = -EINVAL; 227 goto out; 228 } 229 230 ret = filemap_write_and_wait_range(mapping, start, end); 231 232 /* 233 * We need to protect against concurrent writers, which could cause 234 * livelocks in fsync_buffers_list(). 235 */ 236 mutex_lock(&mapping->host->i_mutex); 237 err = fop->fsync(file, dentry, datasync); 238 if (!ret) 239 ret = err; 240 mutex_unlock(&mapping->host->i_mutex); 241 242 out: 243 return ret; 244 } 245 EXPORT_SYMBOL(vfs_fsync_range); 246 247 /** 248 * vfs_fsync - perform a fsync or fdatasync on a file 249 * @file: file to sync 250 * @dentry: dentry of @file 251 * @datasync: only perform a fdatasync operation 252 * 253 * Write back data and metadata for @file to disk. If @datasync is 254 * set only metadata needed to access modified file data is written. 255 * 256 * In case this function is called from nfsd @file may be %NULL and 257 * only @dentry is set. This can only happen when the filesystem 258 * implements the export_operations API. 259 */ 260 int vfs_fsync(struct file *file, struct dentry *dentry, int datasync) 261 { 262 return vfs_fsync_range(file, dentry, 0, LLONG_MAX, datasync); 263 } 264 EXPORT_SYMBOL(vfs_fsync); 265 266 static int do_fsync(unsigned int fd, int datasync) 267 { 268 struct file *file; 269 int ret = -EBADF; 270 271 file = fget(fd); 272 if (file) { 273 ret = vfs_fsync(file, file->f_path.dentry, datasync); 274 fput(file); 275 } 276 return ret; 277 } 278 279 SYSCALL_DEFINE1(fsync, unsigned int, fd) 280 { 281 return do_fsync(fd, 0); 282 } 283 284 SYSCALL_DEFINE1(fdatasync, unsigned int, fd) 285 { 286 return do_fsync(fd, 1); 287 } 288 289 /** 290 * generic_write_sync - perform syncing after a write if file / inode is sync 291 * @file: file to which the write happened 292 * @pos: offset where the write started 293 * @count: length of the write 294 * 295 * This is just a simple wrapper about our general syncing function. 296 */ 297 int generic_write_sync(struct file *file, loff_t pos, loff_t count) 298 { 299 if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host)) 300 return 0; 301 return vfs_fsync_range(file, file->f_path.dentry, pos, 302 pos + count - 1, 303 (file->f_flags & __O_SYNC) ? 0 : 1); 304 } 305 EXPORT_SYMBOL(generic_write_sync); 306 307 /* 308 * sys_sync_file_range() permits finely controlled syncing over a segment of 309 * a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is 310 * zero then sys_sync_file_range() will operate from offset out to EOF. 311 * 312 * The flag bits are: 313 * 314 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range 315 * before performing the write. 316 * 317 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the 318 * range which are not presently under writeback. Note that this may block for 319 * significant periods due to exhaustion of disk request structures. 320 * 321 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range 322 * after performing the write. 323 * 324 * Useful combinations of the flag bits are: 325 * 326 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages 327 * in the range which were dirty on entry to sys_sync_file_range() are placed 328 * under writeout. This is a start-write-for-data-integrity operation. 329 * 330 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which 331 * are not presently under writeout. This is an asynchronous flush-to-disk 332 * operation. Not suitable for data integrity operations. 333 * 334 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for 335 * completion of writeout of all pages in the range. This will be used after an 336 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait 337 * for that operation to complete and to return the result. 338 * 339 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER: 340 * a traditional sync() operation. This is a write-for-data-integrity operation 341 * which will ensure that all pages in the range which were dirty on entry to 342 * sys_sync_file_range() are committed to disk. 343 * 344 * 345 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any 346 * I/O errors or ENOSPC conditions and will return those to the caller, after 347 * clearing the EIO and ENOSPC flags in the address_space. 348 * 349 * It should be noted that none of these operations write out the file's 350 * metadata. So unless the application is strictly performing overwrites of 351 * already-instantiated disk blocks, there are no guarantees here that the data 352 * will be available after a crash. 353 */ 354 SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes, 355 unsigned int flags) 356 { 357 int ret; 358 struct file *file; 359 struct address_space *mapping; 360 loff_t endbyte; /* inclusive */ 361 int fput_needed; 362 umode_t i_mode; 363 364 ret = -EINVAL; 365 if (flags & ~VALID_FLAGS) 366 goto out; 367 368 endbyte = offset + nbytes; 369 370 if ((s64)offset < 0) 371 goto out; 372 if ((s64)endbyte < 0) 373 goto out; 374 if (endbyte < offset) 375 goto out; 376 377 if (sizeof(pgoff_t) == 4) { 378 if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) { 379 /* 380 * The range starts outside a 32 bit machine's 381 * pagecache addressing capabilities. Let it "succeed" 382 */ 383 ret = 0; 384 goto out; 385 } 386 if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) { 387 /* 388 * Out to EOF 389 */ 390 nbytes = 0; 391 } 392 } 393 394 if (nbytes == 0) 395 endbyte = LLONG_MAX; 396 else 397 endbyte--; /* inclusive */ 398 399 ret = -EBADF; 400 file = fget_light(fd, &fput_needed); 401 if (!file) 402 goto out; 403 404 i_mode = file->f_path.dentry->d_inode->i_mode; 405 ret = -ESPIPE; 406 if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) && 407 !S_ISLNK(i_mode)) 408 goto out_put; 409 410 mapping = file->f_mapping; 411 if (!mapping) { 412 ret = -EINVAL; 413 goto out_put; 414 } 415 416 ret = 0; 417 if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) { 418 ret = filemap_fdatawait_range(mapping, offset, endbyte); 419 if (ret < 0) 420 goto out_put; 421 } 422 423 if (flags & SYNC_FILE_RANGE_WRITE) { 424 ret = filemap_fdatawrite_range(mapping, offset, endbyte); 425 if (ret < 0) 426 goto out_put; 427 } 428 429 if (flags & SYNC_FILE_RANGE_WAIT_AFTER) 430 ret = filemap_fdatawait_range(mapping, offset, endbyte); 431 432 out_put: 433 fput_light(file, fput_needed); 434 out: 435 return ret; 436 } 437 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS 438 asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes, 439 long flags) 440 { 441 return SYSC_sync_file_range((int) fd, offset, nbytes, 442 (unsigned int) flags); 443 } 444 SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range); 445 #endif 446 447 /* It would be nice if people remember that not all the world's an i386 448 when they introduce new system calls */ 449 SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags, 450 loff_t offset, loff_t nbytes) 451 { 452 return sys_sync_file_range(fd, offset, nbytes, flags); 453 } 454 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS 455 asmlinkage long SyS_sync_file_range2(long fd, long flags, 456 loff_t offset, loff_t nbytes) 457 { 458 return SYSC_sync_file_range2((int) fd, (unsigned int) flags, 459 offset, nbytes); 460 } 461 SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2); 462 #endif 463