fs/sync.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * High-level sync()-related operations
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/file.h>
   8 #include <linux/fs.h>
   9 #include <linux/slab.h>
  10 #include <linux/export.h>
  11 #include <linux/namei.h>
  12 #include <linux/sched.h>
  13 #include <linux/writeback.h>
  14 #include <linux/syscalls.h>
  15 #include <linux/linkage.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/quotaops.h>
  18 #include <linux/backing-dev.h>
  19 #include "internal.h"
  20
  21 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
  22                         SYNC_FILE_RANGE_WAIT_AFTER)
  23
  24 /*
  25  * Do the filesystem syncing work. For simple filesystems
  26  * writeback_inodes_sb(sb) just dirties buffers with inodes so we have to
  27  * submit IO for these buffers via __sync_blockdev(). This also speeds up the
  28  * wait == 1 case since in that case write_inode() functions do
  29  * sync_dirty_buffer() and thus effectively write one block at a time.
  30  */
  31 static int __sync_filesystem(struct super_block *sb, int wait)
  32 {
  33         if (wait)
  34                 sync_inodes_sb(sb);
  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
  52         /*
  53          * We need to be protected against the filesystem going from
  54          * r/o to r/w or vice versa.
  55          */
  56         WARN_ON(!rwsem_is_locked(&sb->s_umount));
  57
  58         /*
  59          * No point in syncing out anything if the filesystem is read-only.
  60          */
  61         if (sb_rdonly(sb))
  62                 return 0;
  63
  64         ret = __sync_filesystem(sb, 0);
  65         if (ret < 0)
  66                 return ret;
  67         return __sync_filesystem(sb, 1);
  68 }
  69 EXPORT_SYMBOL(sync_filesystem);
  70
  71 static void sync_inodes_one_sb(struct super_block *sb, void *arg)
  72 {
  73         if (!sb_rdonly(sb))
  74                 sync_inodes_sb(sb);
  75 }
  76
  77 static void sync_fs_one_sb(struct super_block *sb, void *arg)
  78 {
  79         if (!sb_rdonly(sb) && !(sb->s_iflags & SB_I_SKIP_SYNC) &&
  80             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         /*
  92          * We keep the error status of individual mapping so that
  93          * applications can catch the writeback error using fsync(2).
  94          * See filemap_fdatawait_keep_errors() for details.
  95          */
  96         filemap_fdatawait_keep_errors(bdev->bd_inode->i_mapping);
  97 }
  98
  99 /*
 100  * Sync everything. We start by waking flusher threads so that most of
 101  * writeback runs on all devices in parallel. Then we sync all inodes reliably
 102  * which effectively also waits for all flusher threads to finish doing
 103  * writeback. At this point all data is on disk so metadata should be stable
 104  * and we tell filesystems to sync their metadata via ->sync_fs() calls.
 105  * Finally, we writeout all block devices because some filesystems (e.g. ext2)
 106  * just write metadata (such as inodes or bitmaps) to block device page cache
 107  * and do not sync it on their own in ->sync_fs().
 108  */
 109 void ksys_sync(void)
 110 {
 111         int nowait = 0, wait = 1;
 112
 113         wakeup_flusher_threads(WB_REASON_SYNC);
 114         iterate_supers(sync_inodes_one_sb, NULL);
 115         iterate_supers(sync_fs_one_sb, &nowait);
 116         iterate_supers(sync_fs_one_sb, &wait);
 117         iterate_bdevs(fdatawrite_one_bdev, NULL);
 118         iterate_bdevs(fdatawait_one_bdev, NULL);
 119         if (unlikely(laptop_mode))
 120                 laptop_sync_completion();
 121 }
 122
 123 SYSCALL_DEFINE0(sync)
 124 {
 125         ksys_sync();
 126         return 0;
 127 }
 128
 129 static void do_sync_work(struct work_struct *work)
 130 {
 131         int nowait = 0;
 132
 133         /*
 134          * Sync twice to reduce the possibility we skipped some inodes / pages
 135          * because they were temporarily locked
 136          */
 137         iterate_supers(sync_inodes_one_sb, &nowait);
 138         iterate_supers(sync_fs_one_sb, &nowait);
 139         iterate_bdevs(fdatawrite_one_bdev, NULL);
 140         iterate_supers(sync_inodes_one_sb, &nowait);
 141         iterate_supers(sync_fs_one_sb, &nowait);
 142         iterate_bdevs(fdatawrite_one_bdev, NULL);
 143         printk("Emergency Sync complete\n");
 144         kfree(work);
 145 }
 146
 147 void emergency_sync(void)
 148 {
 149         struct work_struct *work;
 150
 151         work = kmalloc(sizeof(*work), GFP_ATOMIC);
 152         if (work) {
 153                 INIT_WORK(work, do_sync_work);
 154                 schedule_work(work);
 155         }
 156 }
 157
 158 /*
 159  * sync a single super
 160  */
 161 SYSCALL_DEFINE1(syncfs, int, fd)
 162 {
 163         struct fd f = fdget(fd);
 164         struct super_block *sb;
 165         int ret, ret2;
 166
 167         if (!f.file)
 168                 return -EBADF;
 169         sb = f.file->f_path.dentry->d_sb;
 170
 171         down_read(&sb->s_umount);
 172         ret = sync_filesystem(sb);
 173         up_read(&sb->s_umount);
 174
 175         ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err);
 176
 177         fdput(f);
 178         return ret ? ret : ret2;
 179 }
 180
 181 /**
 182  * vfs_fsync_range - helper to sync a range of data & metadata to disk
 183  * @file:               file to sync
 184  * @start:              offset in bytes of the beginning of data range to sync
 185  * @end:                offset in bytes of the end of data range (inclusive)
 186  * @datasync:           perform only datasync
 187  *
 188  * Write back data in range @start..@end and metadata for @file to disk.  If
 189  * @datasync is set only metadata needed to access modified file data is
 190  * written.
 191  */
 192 int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
 193 {
 194         struct inode *inode = file->f_mapping->host;
 195
 196         if (!file->f_op->fsync)
 197                 return -EINVAL;
 198         if (!datasync && (inode->i_state & I_DIRTY_TIME))
 199                 mark_inode_dirty_sync(inode);
 200         return file->f_op->fsync(file, start, end, datasync);
 201 }
 202 EXPORT_SYMBOL(vfs_fsync_range);
 203
 204 /**
 205  * vfs_fsync - perform a fsync or fdatasync on a file
 206  * @file:               file to sync
 207  * @datasync:           only perform a fdatasync operation
 208  *
 209  * Write back data and metadata for @file to disk.  If @datasync is
 210  * set only metadata needed to access modified file data is written.
 211  */
 212 int vfs_fsync(struct file *file, int datasync)
 213 {
 214         return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
 215 }
 216 EXPORT_SYMBOL(vfs_fsync);
 217
 218 static int do_fsync(unsigned int fd, int datasync)
 219 {
 220         struct fd f = fdget(fd);
 221         int ret = -EBADF;
 222
 223         if (f.file) {
 224                 ret = vfs_fsync(f.file, datasync);
 225                 fdput(f);
 226         }
 227         return ret;
 228 }
 229
 230 SYSCALL_DEFINE1(fsync, unsigned int, fd)
 231 {
 232         return do_fsync(fd, 0);
 233 }
 234
 235 SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
 236 {
 237         return do_fsync(fd, 1);
 238 }
 239
 240 int sync_file_range(struct file *file, loff_t offset, loff_t nbytes,
 241                     unsigned int flags)
 242 {
 243         int ret;
 244         struct address_space *mapping;
 245         loff_t endbyte;                 /* inclusive */
 246         umode_t i_mode;
 247
 248         ret = -EINVAL;
 249         if (flags & ~VALID_FLAGS)
 250                 goto out;
 251
 252         endbyte = offset + nbytes;
 253
 254         if ((s64)offset < 0)
 255                 goto out;
 256         if ((s64)endbyte < 0)
 257                 goto out;
 258         if (endbyte < offset)
 259                 goto out;
 260
 261         if (sizeof(pgoff_t) == 4) {
 262                 if (offset >= (0x100000000ULL << PAGE_SHIFT)) {
 263                         /*
 264                          * The range starts outside a 32 bit machine's
 265                          * pagecache addressing capabilities.  Let it "succeed"
 266                          */
 267                         ret = 0;
 268                         goto out;
 269                 }
 270                 if (endbyte >= (0x100000000ULL << PAGE_SHIFT)) {
 271                         /*
 272                          * Out to EOF
 273                          */
 274                         nbytes = 0;
 275                 }
 276         }
 277
 278         if (nbytes == 0)
 279                 endbyte = LLONG_MAX;
 280         else
 281                 endbyte--;              /* inclusive */
 282
 283         i_mode = file_inode(file)->i_mode;
 284         ret = -ESPIPE;
 285         if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
 286                         !S_ISLNK(i_mode))
 287                 goto out;
 288
 289         mapping = file->f_mapping;
 290         ret = 0;
 291         if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
 292                 ret = file_fdatawait_range(file, offset, endbyte);
 293                 if (ret < 0)
 294                         goto out;
 295         }
 296
 297         if (flags & SYNC_FILE_RANGE_WRITE) {
 298                 int sync_mode = WB_SYNC_NONE;
 299
 300                 if ((flags & SYNC_FILE_RANGE_WRITE_AND_WAIT) ==
 301                              SYNC_FILE_RANGE_WRITE_AND_WAIT)
 302                         sync_mode = WB_SYNC_ALL;
 303
 304                 ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
 305                                                  sync_mode);
 306                 if (ret < 0)
 307                         goto out;
 308         }
 309
 310         if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
 311                 ret = file_fdatawait_range(file, offset, endbyte);
 312
 313 out:
 314         return ret;
 315 }
 316
 317 /*
 318  * ksys_sync_file_range() permits finely controlled syncing over a segment of
 319  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
 320  * zero then ksys_sync_file_range() will operate from offset out to EOF.
 321  *
 322  * The flag bits are:
 323  *
 324  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
 325  * before performing the write.
 326  *
 327  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
 328  * range which are not presently under writeback. Note that this may block for
 329  * significant periods due to exhaustion of disk request structures.
 330  *
 331  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
 332  * after performing the write.
 333  *
 334  * Useful combinations of the flag bits are:
 335  *
 336  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
 337  * in the range which were dirty on entry to ksys_sync_file_range() are placed
 338  * under writeout.  This is a start-write-for-data-integrity operation.
 339  *
 340  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
 341  * are not presently under writeout.  This is an asynchronous flush-to-disk
 342  * operation.  Not suitable for data integrity operations.
 343  *
 344  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
 345  * completion of writeout of all pages in the range.  This will be used after an
 346  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
 347  * for that operation to complete and to return the result.
 348  *
 349  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER
 350  * (a.k.a. SYNC_FILE_RANGE_WRITE_AND_WAIT):
 351  * a traditional sync() operation.  This is a write-for-data-integrity operation
 352  * which will ensure that all pages in the range which were dirty on entry to
 353  * ksys_sync_file_range() are written to disk.  It should be noted that disk
 354  * caches are not flushed by this call, so there are no guarantees here that the
 355  * data will be available on disk after a crash.
 356  *
 357  *
 358  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
 359  * I/O errors or ENOSPC conditions and will return those to the caller, after
 360  * clearing the EIO and ENOSPC flags in the address_space.
 361  *
 362  * It should be noted that none of these operations write out the file's
 363  * metadata.  So unless the application is strictly performing overwrites of
 364  * already-instantiated disk blocks, there are no guarantees here that the data
 365  * will be available after a crash.
 366  */
 367 int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
 368                          unsigned int flags)
 369 {
 370         int ret;
 371         struct fd f;
 372
 373         ret = -EBADF;
 374         f = fdget(fd);
 375         if (f.file)
 376                 ret = sync_file_range(f.file, offset, nbytes, flags);
 377
 378         fdput(f);
 379         return ret;
 380 }
 381
 382 SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 383                                 unsigned int, flags)
 384 {
 385         return ksys_sync_file_range(fd, offset, nbytes, flags);
 386 }
 387
 388 /* It would be nice if people remember that not all the world's an i386
 389    when they introduce new system calls */
 390 SYSCALL_DEFINE4(sync_file_range2, int, fd, unsigned int, flags,
 391                                  loff_t, offset, loff_t, nbytes)
 392 {
 393         return ksys_sync_file_range(fd, offset, nbytes, flags);
 394 }