fs/sync.c

   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