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/xacct.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 SYSCALL_DEFINE0(sync)
 109 {
 110         int nowait = 0, wait = 1;
 111
 112         wakeup_flusher_threads(0, 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         return 0;
 121 }
 122
 123 static void do_sync_work(struct work_struct *work)
 124 {
 125         int nowait = 0;
 126
 127         /*
 128          * Sync twice to reduce the possibility we skipped some inodes / pages
 129          * because they were temporarily locked
 130          */
 131         iterate_supers(sync_inodes_one_sb, &nowait);
 132         iterate_supers(sync_fs_one_sb, &nowait);
 133         iterate_bdevs(fdatawrite_one_bdev, NULL);
 134         iterate_supers(sync_inodes_one_sb, &nowait);
 135         iterate_supers(sync_fs_one_sb, &nowait);
 136         iterate_bdevs(fdatawrite_one_bdev, NULL);
 137         printk("Emergency Sync complete\n");
 138         kfree(work);
 139 }
 140
 141 void emergency_sync(void)
 142 {
 143         struct work_struct *work;
 144
 145         work = kmalloc(sizeof(*work), GFP_ATOMIC);
 146         if (work) {
 147                 INIT_WORK(work, do_sync_work);
 148                 schedule_work(work);
 149         }
 150 }
 151
 152 /*
 153  * sync a single super
 154  */
 155 SYSCALL_DEFINE1(syncfs, int, fd)
 156 {
 157         struct fd f = fdget(fd);
 158         struct super_block *sb;
 159         int ret;
 160
 161         if (!f.file)
 162                 return -EBADF;
 163         sb = f.file->f_path.dentry->d_sb;
 164
 165         down_read(&sb->s_umount);
 166         ret = sync_filesystem(sb);
 167         up_read(&sb->s_umount);
 168
 169         fdput(f);
 170         return ret;
 171 }
 172
 173 /**
 174  * vfs_fsync_range - helper to sync a range of data & metadata to disk
 175  * @file:               file to sync
 176  * @start:              offset in bytes of the beginning of data range to sync
 177  * @end:                offset in bytes of the end of data range (inclusive)
 178  * @datasync:           perform only datasync
 179  *
 180  * Write back data in range @start..@end and metadata for @file to disk.  If
 181  * @datasync is set only metadata needed to access modified file data is
 182  * written.
 183  */
 184 int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
 185 {
 186         struct inode *inode = file->f_mapping->host;
 187
 188         if (!file->f_op->fsync)
 189                 return -EINVAL;
 190         if (!datasync && (inode->i_state & I_DIRTY_TIME)) {
 191                 spin_lock(&inode->i_lock);
 192                 inode->i_state &= ~I_DIRTY_TIME;
 193                 spin_unlock(&inode->i_lock);
 194                 mark_inode_dirty_sync(inode);
 195         }
 196         return file->f_op->fsync(file, start, end, datasync);
 197 }
 198 EXPORT_SYMBOL(vfs_fsync_range);
 199
 200 /**
 201  * vfs_fsync - perform a fsync or fdatasync on a file
 202  * @file:               file to sync
 203  * @datasync:           only perform a fdatasync operation
 204  *
 205  * Write back data and metadata for @file to disk.  If @datasync is
 206  * set only metadata needed to access modified file data is written.
 207  */
 208 int vfs_fsync(struct file *file, int datasync)
 209 {
 210         return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
 211 }
 212 EXPORT_SYMBOL(vfs_fsync);
 213
 214 static int do_fsync(unsigned int fd, int datasync)
 215 {
 216         struct fd f = fdget(fd);
 217         int ret = -EBADF;
 218
 219         if (f.file) {
 220                 ret = vfs_fsync(f.file, datasync);
 221                 fdput(f);
 222                 inc_syscfs(current);
 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 /*
 238  * sys_sync_file_range() permits finely controlled syncing over a segment of
 239  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
 240  * zero then sys_sync_file_range() will operate from offset out to EOF.
 241  *
 242  * The flag bits are:
 243  *
 244  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
 245  * before performing the write.
 246  *
 247  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
 248  * range which are not presently under writeback. Note that this may block for
 249  * significant periods due to exhaustion of disk request structures.
 250  *
 251  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
 252  * after performing the write.
 253  *
 254  * Useful combinations of the flag bits are:
 255  *
 256  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
 257  * in the range which were dirty on entry to sys_sync_file_range() are placed
 258  * under writeout.  This is a start-write-for-data-integrity operation.
 259  *
 260  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
 261  * are not presently under writeout.  This is an asynchronous flush-to-disk
 262  * operation.  Not suitable for data integrity operations.
 263  *
 264  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
 265  * completion of writeout of all pages in the range.  This will be used after an
 266  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
 267  * for that operation to complete and to return the result.
 268  *
 269  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
 270  * a traditional sync() operation.  This is a write-for-data-integrity operation
 271  * which will ensure that all pages in the range which were dirty on entry to
 272  * sys_sync_file_range() are committed to disk.
 273  *
 274  *
 275  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
 276  * I/O errors or ENOSPC conditions and will return those to the caller, after
 277  * clearing the EIO and ENOSPC flags in the address_space.
 278  *
 279  * It should be noted that none of these operations write out the file's
 280  * metadata.  So unless the application is strictly performing overwrites of
 281  * already-instantiated disk blocks, there are no guarantees here that the data
 282  * will be available after a crash.
 283  */
 284 SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 285                                 unsigned int, flags)
 286 {
 287         int ret;
 288         struct fd f;
 289         struct address_space *mapping;
 290         loff_t endbyte;                 /* inclusive */
 291         umode_t i_mode;
 292
 293         ret = -EINVAL;
 294         if (flags & ~VALID_FLAGS)
 295                 goto out;
 296
 297         endbyte = offset + nbytes;
 298
 299         if ((s64)offset < 0)
 300                 goto out;
 301         if ((s64)endbyte < 0)
 302                 goto out;
 303         if (endbyte < offset)
 304                 goto out;
 305
 306         if (sizeof(pgoff_t) == 4) {
 307                 if (offset >= (0x100000000ULL << PAGE_SHIFT)) {
 308                         /*
 309                          * The range starts outside a 32 bit machine's
 310                          * pagecache addressing capabilities.  Let it "succeed"
 311                          */
 312                         ret = 0;
 313                         goto out;
 314                 }
 315                 if (endbyte >= (0x100000000ULL << PAGE_SHIFT)) {
 316                         /*
 317                          * Out to EOF
 318                          */
 319                         nbytes = 0;
 320                 }
 321         }
 322
 323         if (nbytes == 0)
 324                 endbyte = LLONG_MAX;
 325         else
 326                 endbyte--;              /* inclusive */
 327
 328         ret = -EBADF;
 329         f = fdget(fd);
 330         if (!f.file)
 331                 goto out;
 332
 333         i_mode = file_inode(f.file)->i_mode;
 334         ret = -ESPIPE;
 335         if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
 336                         !S_ISLNK(i_mode))
 337                 goto out_put;
 338
 339         mapping = f.file->f_mapping;
 340         ret = 0;
 341         if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
 342                 ret = file_fdatawait_range(f.file, offset, endbyte);
 343                 if (ret < 0)
 344                         goto out_put;
 345         }
 346
 347         if (flags & SYNC_FILE_RANGE_WRITE) {
 348                 ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
 349                                                  WB_SYNC_NONE);
 350                 if (ret < 0)
 351                         goto out_put;
 352         }
 353
 354         if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
 355                 ret = file_fdatawait_range(f.file, offset, endbyte);
 356
 357 out_put:
 358         fdput(f);
 359 out:
 360         return ret;
 361 }
 362
 363 /* It would be nice if people remember that not all the world's an i386
 364    when they introduce new system calls */
 365 SYSCALL_DEFINE4(sync_file_range2, int, fd, unsigned int, flags,
 366                                  loff_t, offset, loff_t, nbytes)
 367 {
 368         return sys_sync_file_range(fd, offset, nbytes, flags);
 369 }