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