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/export.h>
  10 #include <linux/namei.h>
  11 #include <linux/sched.h>
  12 #include <linux/writeback.h>
  13 #include <linux/syscalls.h>
  14 #include <linux/linkage.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/quotaops.h>
  17 #include <linux/backing-dev.h>
  18 #include "internal.h"
  19
  20 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
  21                         SYNC_FILE_RANGE_WAIT_AFTER)
  22
  23 /*
  24  * Do the filesystem syncing work. For simple filesystems
  25  * writeback_inodes_sb(sb) just dirties buffers with inodes so we have to
  26  * submit IO for these buffers via __sync_blockdev(). This also speeds up the
  27  * wait == 1 case since in that case write_inode() functions do
  28  * sync_dirty_buffer() and thus effectively write one block at a time.
  29  */
  30 static int __sync_filesystem(struct super_block *sb, int wait,
  31                              unsigned long start)
  32 {
  33         if (wait)
  34                 sync_inodes_sb(sb, start);
  35         else
  36                 writeback_inodes_sb(sb, WB_REASON_SYNC);
  37
  38         if (sb->s_op->sync_fs)
  39                 sb->s_op->sync_fs(sb, wait);
  40         return __sync_blockdev(sb->s_bdev, wait);
  41 }
  42
  43 /*
  44  * Write out and wait upon all dirty data associated with this
  45  * superblock.  Filesystem data as well as the underlying block
  46  * device.  Takes the superblock lock.
  47  */
  48 int sync_filesystem(struct super_block *sb)
  49 {
  50         int ret;
  51         unsigned long start = jiffies;
  52
  53         /*
  54          * We need to be protected against the filesystem going from
  55          * r/o to r/w or vice versa.
  56          */
  57         WARN_ON(!rwsem_is_locked(&sb->s_umount));
  58
  59         /*
  60          * No point in syncing out anything if the filesystem is read-only.
  61          */
  62         if (sb->s_flags & MS_RDONLY)
  63                 return 0;
  64
  65         ret = __sync_filesystem(sb, 0, start);
  66         if (ret < 0)
  67                 return ret;
  68         return __sync_filesystem(sb, 1, start);
  69 }
  70 EXPORT_SYMBOL_GPL(sync_filesystem);
  71
  72 static void sync_inodes_one_sb(struct super_block *sb, void *arg)
  73 {
  74         if (!(sb->s_flags & MS_RDONLY))
  75                 sync_inodes_sb(sb, *((unsigned long *)arg));
  76 }
  77
  78 static void sync_fs_one_sb(struct super_block *sb, void *arg)
  79 {
  80         if (!(sb->s_flags & MS_RDONLY) && sb->s_op->sync_fs)
  81                 sb->s_op->sync_fs(sb, *(int *)arg);
  82 }
  83
  84 static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
  85 {
  86         filemap_fdatawrite(bdev->bd_inode->i_mapping);
  87 }
  88
  89 static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
  90 {
  91         filemap_fdatawait(bdev->bd_inode->i_mapping);
  92 }
  93
  94 /*
  95  * Sync everything. We start by waking flusher threads so that most of
  96  * writeback runs on all devices in parallel. Then we sync all inodes reliably
  97  * which effectively also waits for all flusher threads to finish doing
  98  * writeback. At this point all data is on disk so metadata should be stable
  99  * and we tell filesystems to sync their metadata via ->sync_fs() calls.
 100  * Finally, we writeout all block devices because some filesystems (e.g. ext2)
 101  * just write metadata (such as inodes or bitmaps) to block device page cache
 102  * and do not sync it on their own in ->sync_fs().
 103  */
 104 SYSCALL_DEFINE0(sync)
 105 {
 106         int nowait = 0, wait = 1;
 107         unsigned long start = jiffies;
 108
 109         wakeup_flusher_threads(0, WB_REASON_SYNC);
 110         iterate_supers(sync_inodes_one_sb, &start);
 111         iterate_supers(sync_fs_one_sb, &nowait);
 112         iterate_supers(sync_fs_one_sb, &wait);
 113         iterate_bdevs(fdatawrite_one_bdev, NULL);
 114         iterate_bdevs(fdatawait_one_bdev, NULL);
 115         if (unlikely(laptop_mode))
 116                 laptop_sync_completion();
 117         return 0;
 118 }
 119
 120 static void do_sync_work(struct work_struct *work)
 121 {
 122         int nowait = 0;
 123
 124         /*
 125          * Sync twice to reduce the possibility we skipped some inodes / pages
 126          * because they were temporarily locked
 127          */
 128         iterate_supers(sync_inodes_one_sb, &nowait);
 129         iterate_supers(sync_fs_one_sb, &nowait);
 130         iterate_bdevs(fdatawrite_one_bdev, NULL);
 131         iterate_supers(sync_inodes_one_sb, &nowait);
 132         iterate_supers(sync_fs_one_sb, &nowait);
 133         iterate_bdevs(fdatawrite_one_bdev, NULL);
 134         printk("Emergency Sync complete\n");
 135         kfree(work);
 136 }
 137
 138 void emergency_sync(void)
 139 {
 140         struct work_struct *work;
 141
 142         work = kmalloc(sizeof(*work), GFP_ATOMIC);
 143         if (work) {
 144                 INIT_WORK(work, do_sync_work);
 145                 schedule_work(work);
 146         }
 147 }
 148
 149 /*
 150  * sync a single super
 151  */
 152 SYSCALL_DEFINE1(syncfs, int, fd)
 153 {
 154         struct fd f = fdget(fd);
 155         struct super_block *sb;
 156         int ret;
 157
 158         if (!f.file)
 159                 return -EBADF;
 160         sb = f.file->f_dentry->d_sb;
 161
 162         down_read(&sb->s_umount);
 163         ret = sync_filesystem(sb);
 164         up_read(&sb->s_umount);
 165
 166         fdput(f);
 167         return ret;
 168 }
 169
 170 /**
 171  * vfs_fsync_range - helper to sync a range of data & metadata to disk
 172  * @file:               file to sync
 173  * @start:              offset in bytes of the beginning of data range to sync
 174  * @end:                offset in bytes of the end of data range (inclusive)
 175  * @datasync:           perform only datasync
 176  *
 177  * Write back data in range @start..@end and metadata for @file to disk.  If
 178  * @datasync is set only metadata needed to access modified file data is
 179  * written.
 180  */
 181 int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
 182 {
 183         if (!file->f_op->fsync)
 184                 return -EINVAL;
 185         return file->f_op->fsync(file, start, end, datasync);
 186 }
 187 EXPORT_SYMBOL(vfs_fsync_range);
 188
 189 /**
 190  * vfs_fsync - perform a fsync or fdatasync on a file
 191  * @file:               file to sync
 192  * @datasync:           only perform a fdatasync operation
 193  *
 194  * Write back data and metadata for @file to disk.  If @datasync is
 195  * set only metadata needed to access modified file data is written.
 196  */
 197 int vfs_fsync(struct file *file, int datasync)
 198 {
 199         return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
 200 }
 201 EXPORT_SYMBOL(vfs_fsync);
 202
 203 static int do_fsync(unsigned int fd, int datasync)
 204 {
 205         struct fd f = fdget(fd);
 206         int ret = -EBADF;
 207
 208         if (f.file) {
 209                 ret = vfs_fsync(f.file, datasync);
 210                 fdput(f);
 211         }
 212         return ret;
 213 }
 214
 215 SYSCALL_DEFINE1(fsync, unsigned int, fd)
 216 {
 217         return do_fsync(fd, 0);
 218 }
 219
 220 SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
 221 {
 222         return do_fsync(fd, 1);
 223 }
 224
 225 /**
 226  * generic_write_sync - perform syncing after a write if file / inode is sync
 227  * @file:       file to which the write happened
 228  * @pos:        offset where the write started
 229  * @count:      length of the write
 230  *
 231  * This is just a simple wrapper about our general syncing function.
 232  */
 233 int generic_write_sync(struct file *file, loff_t pos, loff_t count)
 234 {
 235         if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
 236                 return 0;
 237         return vfs_fsync_range(file, pos, pos + count - 1,
 238                                (file->f_flags & __O_SYNC) ? 0 : 1);
 239 }
 240 EXPORT_SYMBOL(generic_write_sync);
 241
 242 /*
 243  * sys_sync_file_range() permits finely controlled syncing over a segment of
 244  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
 245  * zero then sys_sync_file_range() will operate from offset out to EOF.
 246  *
 247  * The flag bits are:
 248  *
 249  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
 250  * before performing the write.
 251  *
 252  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
 253  * range which are not presently under writeback. Note that this may block for
 254  * significant periods due to exhaustion of disk request structures.
 255  *
 256  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
 257  * after performing the write.
 258  *
 259  * Useful combinations of the flag bits are:
 260  *
 261  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
 262  * in the range which were dirty on entry to sys_sync_file_range() are placed
 263  * under writeout.  This is a start-write-for-data-integrity operation.
 264  *
 265  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
 266  * are not presently under writeout.  This is an asynchronous flush-to-disk
 267  * operation.  Not suitable for data integrity operations.
 268  *
 269  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
 270  * completion of writeout of all pages in the range.  This will be used after an
 271  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
 272  * for that operation to complete and to return the result.
 273  *
 274  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
 275  * a traditional sync() operation.  This is a write-for-data-integrity operation
 276  * which will ensure that all pages in the range which were dirty on entry to
 277  * sys_sync_file_range() are committed to disk.
 278  *
 279  *
 280  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
 281  * I/O errors or ENOSPC conditions and will return those to the caller, after
 282  * clearing the EIO and ENOSPC flags in the address_space.
 283  *
 284  * It should be noted that none of these operations write out the file's
 285  * metadata.  So unless the application is strictly performing overwrites of
 286  * already-instantiated disk blocks, there are no guarantees here that the data
 287  * will be available after a crash.
 288  */
 289 SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 290                                 unsigned int, flags)
 291 {
 292         int ret;
 293         struct fd f;
 294         struct address_space *mapping;
 295         loff_t endbyte;                 /* inclusive */
 296         umode_t i_mode;
 297
 298         ret = -EINVAL;
 299         if (flags & ~VALID_FLAGS)
 300                 goto out;
 301
 302         endbyte = offset + nbytes;
 303
 304         if ((s64)offset < 0)
 305                 goto out;
 306         if ((s64)endbyte < 0)
 307                 goto out;
 308         if (endbyte < offset)
 309                 goto out;
 310
 311         if (sizeof(pgoff_t) == 4) {
 312                 if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
 313                         /*
 314                          * The range starts outside a 32 bit machine's
 315                          * pagecache addressing capabilities.  Let it "succeed"
 316                          */
 317                         ret = 0;
 318                         goto out;
 319                 }
 320                 if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
 321                         /*
 322                          * Out to EOF
 323                          */
 324                         nbytes = 0;
 325                 }
 326         }
 327
 328         if (nbytes == 0)
 329                 endbyte = LLONG_MAX;
 330         else
 331                 endbyte--;              /* inclusive */
 332
 333         ret = -EBADF;
 334         f = fdget(fd);
 335         if (!f.file)
 336                 goto out;
 337
 338         i_mode = file_inode(f.file)->i_mode;
 339         ret = -ESPIPE;
 340         if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
 341                         !S_ISLNK(i_mode))
 342                 goto out_put;
 343
 344         mapping = f.file->f_mapping;
 345         if (!mapping) {
 346                 ret = -EINVAL;
 347                 goto out_put;
 348         }
 349
 350         ret = 0;
 351         if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
 352                 ret = filemap_fdatawait_range(mapping, offset, endbyte);
 353                 if (ret < 0)
 354                         goto out_put;
 355         }
 356
 357         if (flags & SYNC_FILE_RANGE_WRITE) {
 358                 ret = filemap_fdatawrite_range(mapping, offset, endbyte);
 359                 if (ret < 0)
 360                         goto out_put;
 361         }
 362
 363         if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
 364                 ret = filemap_fdatawait_range(mapping, offset, endbyte);
 365
 366 out_put:
 367         fdput(f);
 368 out:
 369         return ret;
 370 }
 371
 372 /* It would be nice if people remember that not all the world's an i386
 373    when they introduce new system calls */
 374 SYSCALL_DEFINE4(sync_file_range2, int, fd, unsigned int, flags,
 375                                  loff_t, offset, loff_t, nbytes)
 376 {
 377         return sys_sync_file_range(fd, offset, nbytes, flags);
 378 }