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{
  32        /*
  33         * This should be safe, as we require bdi backing to actually
  34         * write out data in the first place
  35         */
  36        if (sb->s_bdi == &noop_backing_dev_info)
  37                return 0;
  38
  39        if (sb->s_qcop && sb->s_qcop->quota_sync)
  40                sb->s_qcop->quota_sync(sb, -1, wait);
  41
  42        if (wait)
  43                sync_inodes_sb(sb);
  44        else
  45                writeback_inodes_sb(sb, WB_REASON_SYNC);
  46
  47        if (sb->s_op->sync_fs)
  48                sb->s_op->sync_fs(sb, wait);
  49        return __sync_blockdev(sb->s_bdev, wait);
  50}
  51
  52/*
  53 * Write out and wait upon all dirty data associated with this
  54 * superblock.  Filesystem data as well as the underlying block
  55 * device.  Takes the superblock lock.
  56 */
  57int sync_filesystem(struct super_block *sb)
  58{
  59        int ret;
  60
  61        /*
  62         * We need to be protected against the filesystem going from
  63         * r/o to r/w or vice versa.
  64         */
  65        WARN_ON(!rwsem_is_locked(&sb->s_umount));
  66
  67        /*
  68         * No point in syncing out anything if the filesystem is read-only.
  69         */
  70        if (sb->s_flags & MS_RDONLY)
  71                return 0;
  72
  73        ret = __sync_filesystem(sb, 0);
  74        if (ret < 0)
  75                return ret;
  76        return __sync_filesystem(sb, 1);
  77}
  78EXPORT_SYMBOL_GPL(sync_filesystem);
  79
  80static void sync_one_sb(struct super_block *sb, void *arg)
  81{
  82        if (!(sb->s_flags & MS_RDONLY))
  83                __sync_filesystem(sb, *(int *)arg);
  84}
  85/*
  86 * Sync all the data for all the filesystems (called by sys_sync() and
  87 * emergency sync)
  88 */
  89static void sync_filesystems(int wait)
  90{
  91        iterate_supers(sync_one_sb, &wait);
  92}
  93
  94/*
  95 * sync everything.  Start out by waking pdflush, because that writes back
  96 * all queues in parallel.
  97 */
  98SYSCALL_DEFINE0(sync)
  99{
 100        wakeup_flusher_threads(0, WB_REASON_SYNC);
 101        sync_filesystems(0);
 102        sync_filesystems(1);
 103        if (unlikely(laptop_mode))
 104                laptop_sync_completion();
 105        return 0;
 106}
 107
 108static void do_sync_work(struct work_struct *work)
 109{
 110        /*
 111         * Sync twice to reduce the possibility we skipped some inodes / pages
 112         * because they were temporarily locked
 113         */
 114        sync_filesystems(0);
 115        sync_filesystems(0);
 116        printk("Emergency Sync complete\n");
 117        kfree(work);
 118}
 119
 120void emergency_sync(void)
 121{
 122        struct work_struct *work;
 123
 124        work = kmalloc(sizeof(*work), GFP_ATOMIC);
 125        if (work) {
 126                INIT_WORK(work, do_sync_work);
 127                schedule_work(work);
 128        }
 129}
 130
 131/*
 132 * sync a single super
 133 */
 134SYSCALL_DEFINE1(syncfs, int, fd)
 135{
 136        struct file *file;
 137        struct super_block *sb;
 138        int ret;
 139        int fput_needed;
 140
 141        file = fget_light(fd, &fput_needed);
 142        if (!file)
 143                return -EBADF;
 144        sb = file->f_dentry->d_sb;
 145
 146        down_read(&sb->s_umount);
 147        ret = sync_filesystem(sb);
 148        up_read(&sb->s_umount);
 149
 150        fput_light(file, fput_needed);
 151        return ret;
 152}
 153
 154/**
 155 * vfs_fsync_range - helper to sync a range of data & metadata to disk
 156 * @file:               file to sync
 157 * @start:              offset in bytes of the beginning of data range to sync
 158 * @end:                offset in bytes of the end of data range (inclusive)
 159 * @datasync:           perform only datasync
 160 *
 161 * Write back data in range @start..@end and metadata for @file to disk.  If
 162 * @datasync is set only metadata needed to access modified file data is
 163 * written.
 164 */
 165int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
 166{
 167        if (!file->f_op || !file->f_op->fsync)
 168                return -EINVAL;
 169        return file->f_op->fsync(file, start, end, datasync);
 170}
 171EXPORT_SYMBOL(vfs_fsync_range);
 172
 173/**
 174 * vfs_fsync - perform a fsync or fdatasync on a file
 175 * @file:               file to sync
 176 * @datasync:           only perform a fdatasync operation
 177 *
 178 * Write back data and metadata for @file to disk.  If @datasync is
 179 * set only metadata needed to access modified file data is written.
 180 */
 181int vfs_fsync(struct file *file, int datasync)
 182{
 183        return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
 184}
 185EXPORT_SYMBOL(vfs_fsync);
 186
 187static int do_fsync(unsigned int fd, int datasync)
 188{
 189        struct file *file;
 190        int ret = -EBADF;
 191        int fput_needed;
 192
 193        file = fget_light(fd, &fput_needed);
 194        if (file) {
 195                ret = vfs_fsync(file, datasync);
 196                fput_light(file, fput_needed);
 197        }
 198        return ret;
 199}
 200
 201SYSCALL_DEFINE1(fsync, unsigned int, fd)
 202{
 203        return do_fsync(fd, 0);
 204}
 205
 206SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
 207{
 208        return do_fsync(fd, 1);
 209}
 210
 211/**
 212 * generic_write_sync - perform syncing after a write if file / inode is sync
 213 * @file:       file to which the write happened
 214 * @pos:        offset where the write started
 215 * @count:      length of the write
 216 *
 217 * This is just a simple wrapper about our general syncing function.
 218 */
 219int generic_write_sync(struct file *file, loff_t pos, loff_t count)
 220{
 221        if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
 222                return 0;
 223        return vfs_fsync_range(file, pos, pos + count - 1,
 224                               (file->f_flags & __O_SYNC) ? 0 : 1);
 225}
 226EXPORT_SYMBOL(generic_write_sync);
 227
 228/*
 229 * sys_sync_file_range() permits finely controlled syncing over a segment of
 230 * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
 231 * zero then sys_sync_file_range() will operate from offset out to EOF.
 232 *
 233 * The flag bits are:
 234 *
 235 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
 236 * before performing the write.
 237 *
 238 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
 239 * range which are not presently under writeback. Note that this may block for
 240 * significant periods due to exhaustion of disk request structures.
 241 *
 242 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
 243 * after performing the write.
 244 *
 245 * Useful combinations of the flag bits are:
 246 *
 247 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
 248 * in the range which were dirty on entry to sys_sync_file_range() are placed
 249 * under writeout.  This is a start-write-for-data-integrity operation.
 250 *
 251 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
 252 * are not presently under writeout.  This is an asynchronous flush-to-disk
 253 * operation.  Not suitable for data integrity operations.
 254 *
 255 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
 256 * completion of writeout of all pages in the range.  This will be used after an
 257 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
 258 * for that operation to complete and to return the result.
 259 *
 260 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
 261 * a traditional sync() operation.  This is a write-for-data-integrity operation
 262 * which will ensure that all pages in the range which were dirty on entry to
 263 * sys_sync_file_range() are committed to disk.
 264 *
 265 *
 266 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
 267 * I/O errors or ENOSPC conditions and will return those to the caller, after
 268 * clearing the EIO and ENOSPC flags in the address_space.
 269 *
 270 * It should be noted that none of these operations write out the file's
 271 * metadata.  So unless the application is strictly performing overwrites of
 272 * already-instantiated disk blocks, there are no guarantees here that the data
 273 * will be available after a crash.
 274 */
 275SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
 276                                unsigned int flags)
 277{
 278        int ret;
 279        struct file *file;
 280        struct address_space *mapping;
 281        loff_t endbyte;                 /* inclusive */
 282        int fput_needed;
 283        umode_t i_mode;
 284
 285        ret = -EINVAL;
 286        if (flags & ~VALID_FLAGS)
 287                goto out;
 288
 289        endbyte = offset + nbytes;
 290
 291        if ((s64)offset < 0)
 292                goto out;
 293        if ((s64)endbyte < 0)
 294                goto out;
 295        if (endbyte < offset)
 296                goto out;
 297
 298        if (sizeof(pgoff_t) == 4) {
 299                if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
 300                        /*
 301                         * The range starts outside a 32 bit machine's
 302                         * pagecache addressing capabilities.  Let it "succeed"
 303                         */
 304                        ret = 0;
 305                        goto out;
 306                }
 307                if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
 308                        /*
 309                         * Out to EOF
 310                         */
 311                        nbytes = 0;
 312                }
 313        }
 314
 315        if (nbytes == 0)
 316                endbyte = LLONG_MAX;
 317        else
 318                endbyte--;              /* inclusive */
 319
 320        ret = -EBADF;
 321        file = fget_light(fd, &fput_needed);
 322        if (!file)
 323                goto out;
 324
 325        i_mode = file->f_path.dentry->d_inode->i_mode;
 326        ret = -ESPIPE;
 327        if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
 328                        !S_ISLNK(i_mode))
 329                goto out_put;
 330
 331        mapping = file->f_mapping;
 332        if (!mapping) {
 333                ret = -EINVAL;
 334                goto out_put;
 335        }
 336
 337        ret = 0;
 338        if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
 339                ret = filemap_fdatawait_range(mapping, offset, endbyte);
 340                if (ret < 0)
 341                        goto out_put;
 342        }
 343
 344        if (flags & SYNC_FILE_RANGE_WRITE) {
 345                ret = filemap_fdatawrite_range(mapping, offset, endbyte);
 346                if (ret < 0)
 347                        goto out_put;
 348        }
 349
 350        if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
 351                ret = filemap_fdatawait_range(mapping, offset, endbyte);
 352
 353out_put:
 354        fput_light(file, fput_needed);
 355out:
 356        return ret;
 357}
 358#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 359asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
 360                                    long flags)
 361{
 362        return SYSC_sync_file_range((int) fd, offset, nbytes,
 363                                    (unsigned int) flags);
 364}
 365SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
 366#endif
 367
 368/* It would be nice if people remember that not all the world's an i386
 369   when they introduce new system calls */
 370SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
 371                                 loff_t offset, loff_t nbytes)
 372{
 373        return sys_sync_file_range(fd, offset, nbytes, flags);
 374}
 375#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 376asmlinkage long SyS_sync_file_range2(long fd, long flags,
 377                                     loff_t offset, loff_t nbytes)
 378{
 379        return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
 380                                     offset, nbytes);
 381}
 382SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
 383#endif
 384
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