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_op->sync_fs)
  80                 sb->s_op->sync_fs(sb, *(int *)arg);
  81 }
  82
  83 static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
  84 {
  85         filemap_fdatawrite(bdev->bd_inode->i_mapping);
  86 }
  87
  88 static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
  89 {
  90         /*
  91          * We keep the error status of individual mapping so that
  92          * applications can catch the writeback error using fsync(2).
  93          * See filemap_fdatawait_keep_errors() for details.
  94          */
  95         filemap_fdatawait_keep_errors(bdev->bd_inode->i_mapping);
  96 }
  97
  98 /*
  99  * Sync everything. We start by waking flusher threads so that most of
 100  * writeback runs on all devices in parallel. Then we sync all inodes reliably
 101  * which effectively also waits for all flusher threads to finish doing
 102  * writeback. At this point all data is on disk so metadata should be stable
 103  * and we tell filesystems to sync their metadata via ->sync_fs() calls.
 104  * Finally, we writeout all block devices because some filesystems (e.g. ext2)
 105  * just write metadata (such as inodes or bitmaps) to block device page cache
 106  * and do not sync it on their own in ->sync_fs().
 107  */
 108 void ksys_sync(void)
 109 {
 110         int nowait = 0, wait = 1;
 111
 112         wakeup_flusher_threads(WB_REASON_SYNC);
 113         iterate_supers(sync_inodes_one_sb, NULL);
 114         iterate_supers(sync_fs_one_sb, &nowait);
 115         iterate_supers(sync_fs_one_sb, &wait);
 116         iterate_bdevs(fdatawrite_one_bdev, NULL);
 117         iterate_bdevs(fdatawait_one_bdev, NULL);
 118         if (unlikely(laptop_mode))
 119                 laptop_sync_completion();
 120 }
 121
 122 SYSCALL_DEFINE0(sync)
 123 {
 124         ksys_sync();
 125         return 0;
 126 }
 127
 128 static void do_sync_work(struct work_struct *work)
 129 {
 130         int nowait = 0;
 131
 132         /*
 133          * Sync twice to reduce the possibility we skipped some inodes / pages
 134          * because they were temporarily locked
 135          */
 136         iterate_supers(sync_inodes_one_sb, &nowait);
 137         iterate_supers(sync_fs_one_sb, &nowait);
 138         iterate_bdevs(fdatawrite_one_bdev, NULL);
 139         iterate_supers(sync_inodes_one_sb, &nowait);
 140         iterate_supers(sync_fs_one_sb, &nowait);
 141         iterate_bdevs(fdatawrite_one_bdev, NULL);
 142         printk("Emergency Sync complete\n");
 143         kfree(work);
 144 }
 145
 146 void emergency_sync(void)
 147 {
 148         struct work_struct *work;
 149
 150         work = kmalloc(sizeof(*work), GFP_ATOMIC);
 151         if (work) {
 152                 INIT_WORK(work, do_sync_work);
 153                 schedule_work(work);
 154         }
 155 }
 156
 157 /*
 158  * sync a single super
 159  */
 160 SYSCALL_DEFINE1(syncfs, int, fd)
 161 {
 162         struct fd f = fdget(fd);
 163         struct super_block *sb;
 164         int ret;
 165
 166         if (!f.file)
 167                 return -EBADF;
 168         sb = f.file->f_path.dentry->d_sb;
 169
 170         down_read(&sb->s_umount);
 171         ret = sync_filesystem(sb);
 172         up_read(&sb->s_umount);
 173
 174         fdput(f);
 175         return ret;
 176 }
 177
 178 /**
 179  * vfs_fsync_range - helper to sync a range of data & metadata to disk
 180  * @file:               file to sync
 181  * @start:              offset in bytes of the beginning of data range to sync
 182  * @end:                offset in bytes of the end of data range (inclusive)
 183  * @datasync:           perform only datasync
 184  *
 185  * Write back data in range @start..@end and metadata for @file to disk.  If
 186  * @datasync is set only metadata needed to access modified file data is
 187  * written.
 188  */
 189 int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
 190 {
 191         struct inode *inode = file->f_mapping->host;
 192
 193         if (!file->f_op->fsync)
 194                 return -EINVAL;
 195         if (!datasync && (inode->i_state & I_DIRTY_TIME))
 196                 mark_inode_dirty_sync(inode);
 197         return file->f_op->fsync(file, start, end, datasync);
 198 }
 199 EXPORT_SYMBOL(vfs_fsync_range);
 200
 201 /**
 202  * vfs_fsync - perform a fsync or fdatasync on a file
 203  * @file:               file to sync
 204  * @datasync:           only perform a fdatasync operation
 205  *
 206  * Write back data and metadata for @file to disk.  If @datasync is
 207  * set only metadata needed to access modified file data is written.
 208  */
 209 int vfs_fsync(struct file *file, int datasync)
 210 {
 211         return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
 212 }
 213 EXPORT_SYMBOL(vfs_fsync);
 214
 215 static int do_fsync(unsigned int fd, int datasync)
 216 {
 217         struct fd f = fdget(fd);
 218         int ret = -EBADF;
 219
 220         if (f.file) {
 221                 ret = vfs_fsync(f.file, datasync);
 222                 fdput(f);
 223         }
 224         return ret;
 225 }
 226
 227 SYSCALL_DEFINE1(fsync, unsigned int, fd)
 228 {
 229         return do_fsync(fd, 0);
 230 }
 231
 232 SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
 233 {
 234         return do_fsync(fd, 1);
 235 }
 236
 237 int sync_file_range(struct file *file, loff_t offset, loff_t nbytes,
 238                     unsigned int flags)
 239 {
 240         int ret;
 241         struct address_space *mapping;
 242         loff_t endbyte;                 /* inclusive */
 243         umode_t i_mode;
 244
 245         ret = -EINVAL;
 246         if (flags & ~VALID_FLAGS)
 247                 goto out;
 248
 249         endbyte = offset + nbytes;
 250
 251         if ((s64)offset < 0)
 252                 goto out;
 253         if ((s64)endbyte < 0)
 254                 goto out;
 255         if (endbyte < offset)
 256                 goto out;
 257
 258         if (sizeof(pgoff_t) == 4) {
 259                 if (offset >= (0x100000000ULL << PAGE_SHIFT)) {
 260                         /*
 261                          * The range starts outside a 32 bit machine's
 262                          * pagecache addressing capabilities.  Let it "succeed"
 263                          */
 264                         ret = 0;
 265                         goto out;
 266                 }
 267                 if (endbyte >= (0x100000000ULL << PAGE_SHIFT)) {
 268                         /*
 269                          * Out to EOF
 270                          */
 271                         nbytes = 0;
 272                 }
 273         }
 274
 275         if (nbytes == 0)
 276                 endbyte = LLONG_MAX;
 277         else
 278                 endbyte--;              /* inclusive */
 279
 280         i_mode = file_inode(file)->i_mode;
 281         ret = -ESPIPE;
 282         if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
 283                         !S_ISLNK(i_mode))
 284                 goto out;
 285
 286         mapping = file->f_mapping;
 287         ret = 0;
 288         if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
 289                 ret = file_fdatawait_range(file, offset, endbyte);
 290                 if (ret < 0)
 291                         goto out;
 292         }
 293
 294         if (flags & SYNC_FILE_RANGE_WRITE) {
 295                 int sync_mode = WB_SYNC_NONE;
 296
 297                 if ((flags & SYNC_FILE_RANGE_WRITE_AND_WAIT) ==
 298                              SYNC_FILE_RANGE_WRITE_AND_WAIT)
 299                         sync_mode = WB_SYNC_ALL;
 300
 301                 ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
 302                                                  sync_mode);
 303                 if (ret < 0)
 304                         goto out;
 305         }
 306
 307         if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
 308                 ret = file_fdatawait_range(file, offset, endbyte);
 309
 310 out:
 311         return ret;
 312 }
 313
 314 /*
 315  * ksys_sync_file_range() permits finely controlled syncing over a segment of
 316  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
 317  * zero then ksys_sync_file_range() will operate from offset out to EOF.
 318  *
 319  * The flag bits are:
 320  *
 321  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
 322  * before performing the write.
 323  *
 324  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
 325  * range which are not presently under writeback. Note that this may block for
 326  * significant periods due to exhaustion of disk request structures.
 327  *
 328  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
 329  * after performing the write.
 330  *
 331  * Useful combinations of the flag bits are:
 332  *
 333  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
 334  * in the range which were dirty on entry to ksys_sync_file_range() are placed
 335  * under writeout.  This is a start-write-for-data-integrity operation.
 336  *
 337  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
 338  * are not presently under writeout.  This is an asynchronous flush-to-disk
 339  * operation.  Not suitable for data integrity operations.
 340  *
 341  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
 342  * completion of writeout of all pages in the range.  This will be used after an
 343  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
 344  * for that operation to complete and to return the result.
 345  *
 346  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER
 347  * (a.k.a. SYNC_FILE_RANGE_WRITE_AND_WAIT):
 348  * a traditional sync() operation.  This is a write-for-data-integrity operation
 349  * which will ensure that all pages in the range which were dirty on entry to
 350  * ksys_sync_file_range() are written to disk.  It should be noted that disk
 351  * caches are not flushed by this call, so there are no guarantees here that the
 352  * data will be available on disk after a crash.
 353  *
 354  *
 355  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
 356  * I/O errors or ENOSPC conditions and will return those to the caller, after
 357  * clearing the EIO and ENOSPC flags in the address_space.
 358  *
 359  * It should be noted that none of these operations write out the file's
 360  * metadata.  So unless the application is strictly performing overwrites of
 361  * already-instantiated disk blocks, there are no guarantees here that the data
 362  * will be available after a crash.
 363  */
 364 int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
 365                          unsigned int flags)
 366 {
 367         int ret;
 368         struct fd f;
 369
 370         ret = -EBADF;
 371         f = fdget(fd);
 372         if (f.file)
 373                 ret = sync_file_range(f.file, offset, nbytes, flags);
 374
 375         fdput(f);
 376         return ret;
 377 }
 378
 379 SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 380                                 unsigned int, flags)
 381 {
 382         return ksys_sync_file_range(fd, offset, nbytes, flags);
 383 }
 384
 385 /* It would be nice if people remember that not all the world's an i386
 386    when they introduce new system calls */
 387 SYSCALL_DEFINE4(sync_file_range2, int, fd, unsigned int, flags,
 388                                  loff_t, offset, loff_t, nbytes)
 389 {
 390         return ksys_sync_file_range(fd, offset, nbytes, flags);
 391 }