fs/sync.c

   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/module.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  */
  30 static 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  */
  57 int 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 }
  78 EXPORT_SYMBOL_GPL(sync_filesystem);
  79
  80 static 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  */
  89 static 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  */
  98 SYSCALL_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
 108 static 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
 120 void 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  */
 134 SYSCALL_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  */
 165 int 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 }
 171 EXPORT_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  */
 181 int vfs_fsync(struct file *file, int datasync)
 182 {
 183         return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
 184 }
 185 EXPORT_SYMBOL(vfs_fsync);
 186
 187 static int do_fsync(unsigned int fd, int datasync)
 188 {
 189         struct file *file;
 190         int ret = -EBADF;
 191
 192         file = fget(fd);
 193         if (file) {
 194                 ret = vfs_fsync(file, datasync);
 195                 fput(file);
 196         }
 197         return ret;
 198 }
 199
 200 SYSCALL_DEFINE1(fsync, unsigned int, fd)
 201 {
 202         return do_fsync(fd, 0);
 203 }
 204
 205 SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
 206 {
 207         return do_fsync(fd, 1);
 208 }
 209
 210 /**
 211  * generic_write_sync - perform syncing after a write if file / inode is sync
 212  * @file:       file to which the write happened
 213  * @pos:        offset where the write started
 214  * @count:      length of the write
 215  *
 216  * This is just a simple wrapper about our general syncing function.
 217  */
 218 int generic_write_sync(struct file *file, loff_t pos, loff_t count)
 219 {
 220         if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
 221                 return 0;
 222         return vfs_fsync_range(file, pos, pos + count - 1,
 223                                (file->f_flags & __O_SYNC) ? 0 : 1);
 224 }
 225 EXPORT_SYMBOL(generic_write_sync);
 226
 227 /*
 228  * sys_sync_file_range() permits finely controlled syncing over a segment of
 229  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
 230  * zero then sys_sync_file_range() will operate from offset out to EOF.
 231  *
 232  * The flag bits are:
 233  *
 234  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
 235  * before performing the write.
 236  *
 237  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
 238  * range which are not presently under writeback. Note that this may block for
 239  * significant periods due to exhaustion of disk request structures.
 240  *
 241  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
 242  * after performing the write.
 243  *
 244  * Useful combinations of the flag bits are:
 245  *
 246  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
 247  * in the range which were dirty on entry to sys_sync_file_range() are placed
 248  * under writeout.  This is a start-write-for-data-integrity operation.
 249  *
 250  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
 251  * are not presently under writeout.  This is an asynchronous flush-to-disk
 252  * operation.  Not suitable for data integrity operations.
 253  *
 254  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
 255  * completion of writeout of all pages in the range.  This will be used after an
 256  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
 257  * for that operation to complete and to return the result.
 258  *
 259  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
 260  * a traditional sync() operation.  This is a write-for-data-integrity operation
 261  * which will ensure that all pages in the range which were dirty on entry to
 262  * sys_sync_file_range() are committed to disk.
 263  *
 264  *
 265  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
 266  * I/O errors or ENOSPC conditions and will return those to the caller, after
 267  * clearing the EIO and ENOSPC flags in the address_space.
 268  *
 269  * It should be noted that none of these operations write out the file's
 270  * metadata.  So unless the application is strictly performing overwrites of
 271  * already-instantiated disk blocks, there are no guarantees here that the data
 272  * will be available after a crash.
 273  */
 274 SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
 275                                 unsigned int flags)
 276 {
 277         int ret;
 278         struct file *file;
 279         struct address_space *mapping;
 280         loff_t endbyte;                 /* inclusive */
 281         int fput_needed;
 282         umode_t i_mode;
 283
 284         ret = -EINVAL;
 285         if (flags & ~VALID_FLAGS)
 286                 goto out;
 287
 288         endbyte = offset + nbytes;
 289
 290         if ((s64)offset < 0)
 291                 goto out;
 292         if ((s64)endbyte < 0)
 293                 goto out;
 294         if (endbyte < offset)
 295                 goto out;
 296
 297         if (sizeof(pgoff_t) == 4) {
 298                 if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
 299                         /*
 300                          * The range starts outside a 32 bit machine's
 301                          * pagecache addressing capabilities.  Let it "succeed"
 302                          */
 303                         ret = 0;
 304                         goto out;
 305                 }
 306                 if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
 307                         /*
 308                          * Out to EOF
 309                          */
 310                         nbytes = 0;
 311                 }
 312         }
 313
 314         if (nbytes == 0)
 315                 endbyte = LLONG_MAX;
 316         else
 317                 endbyte--;              /* inclusive */
 318
 319         ret = -EBADF;
 320         file = fget_light(fd, &fput_needed);
 321         if (!file)
 322                 goto out;
 323
 324         i_mode = file->f_path.dentry->d_inode->i_mode;
 325         ret = -ESPIPE;
 326         if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
 327                         !S_ISLNK(i_mode))
 328                 goto out_put;
 329
 330         mapping = file->f_mapping;
 331         if (!mapping) {
 332                 ret = -EINVAL;
 333                 goto out_put;
 334         }
 335
 336         ret = 0;
 337         if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
 338                 ret = filemap_fdatawait_range(mapping, offset, endbyte);
 339                 if (ret < 0)
 340                         goto out_put;
 341         }
 342
 343         if (flags & SYNC_FILE_RANGE_WRITE) {
 344                 ret = filemap_fdatawrite_range(mapping, offset, endbyte);
 345                 if (ret < 0)
 346                         goto out_put;
 347         }
 348
 349         if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
 350                 ret = filemap_fdatawait_range(mapping, offset, endbyte);
 351
 352 out_put:
 353         fput_light(file, fput_needed);
 354 out:
 355         return ret;
 356 }
 357 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 358 asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
 359                                     long flags)
 360 {
 361         return SYSC_sync_file_range((int) fd, offset, nbytes,
 362                                     (unsigned int) flags);
 363 }
 364 SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
 365 #endif
 366
 367 /* It would be nice if people remember that not all the world's an i386
 368    when they introduce new system calls */
 369 SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
 370                                  loff_t offset, loff_t nbytes)
 371 {
 372         return sys_sync_file_range(fd, offset, nbytes, flags);
 373 }
 374 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 375 asmlinkage long SyS_sync_file_range2(long fd, long flags,
 376                                      loff_t offset, loff_t nbytes)
 377 {
 378         return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
 379                                      offset, nbytes);
 380 }
 381 SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
 382 #endif