linux/fs/sync.c
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   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 */
  31static 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 */
  48int 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}
  69EXPORT_SYMBOL(sync_filesystem);
  70
  71static void sync_inodes_one_sb(struct super_block *sb, void *arg)
  72{
  73        if (!sb_rdonly(sb))
  74                sync_inodes_sb(sb);
  75}
  76
  77static 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
  84static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
  85{
  86        filemap_fdatawrite(bdev->bd_inode->i_mapping);
  87}
  88
  89static 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 */
 109void 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
 123SYSCALL_DEFINE0(sync)
 124{
 125        ksys_sync();
 126        return 0;
 127}
 128
 129static 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
 147void 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 */
 161SYSCALL_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 */
 192int 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}
 202EXPORT_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 */
 212int vfs_fsync(struct file *file, int datasync)
 213{
 214        return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
 215}
 216EXPORT_SYMBOL(vfs_fsync);
 217
 218static 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
 230SYSCALL_DEFINE1(fsync, unsigned int, fd)
 231{
 232        return do_fsync(fd, 0);
 233}
 234
 235SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
 236{
 237        return do_fsync(fd, 1);
 238}
 239
 240int 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
 313out:
 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 */
 367int 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
 382SYSCALL_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 */
 390SYSCALL_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}
 395
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