linux/fs/sync.c
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   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 */
  30static 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 */
  48int 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}
  70EXPORT_SYMBOL_GPL(sync_filesystem);
  71
  72static 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
  78static 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
  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        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 */
 104SYSCALL_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
 120static 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
 138void 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 */
 152SYSCALL_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 */
 181int 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}
 187EXPORT_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 */
 197int vfs_fsync(struct file *file, int datasync)
 198{
 199        return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
 200}
 201EXPORT_SYMBOL(vfs_fsync);
 202
 203static 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
 215SYSCALL_DEFINE1(fsync, unsigned int, fd)
 216{
 217        return do_fsync(fd, 0);
 218}
 219
 220SYSCALL_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 */
 233int 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}
 240EXPORT_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 */
 289SYSCALL_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
 366out_put:
 367        fdput(f);
 368out:
 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 */
 374SYSCALL_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}
 379