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/module.h>
   9 #include <linux/sched.h>
  10 #include <linux/writeback.h>
  11 #include <linux/syscalls.h>
  12 #include <linux/linkage.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/quotaops.h>
  15 #include <linux/buffer_head.h>
  16 #include "internal.h"
  17
  18 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
  19                         SYNC_FILE_RANGE_WAIT_AFTER)
  20
  21 /*
  22  * Do the filesystem syncing work. For simple filesystems sync_inodes_sb(sb, 0)
  23  * just dirties buffers with inodes so we have to submit IO for these buffers
  24  * via __sync_blockdev(). This also speeds up the wait == 1 case since in that
  25  * case write_inode() functions do sync_dirty_buffer() and thus effectively
  26  * write one block at a time.
  27  */
  28 static int __sync_filesystem(struct super_block *sb, int wait)
  29 {
  30         /* Avoid doing twice syncing and cache pruning for quota sync */
  31         if (!wait)
  32                 writeout_quota_sb(sb, -1);
  33         else
  34                 sync_quota_sb(sb, -1);
  35         sync_inodes_sb(sb, wait);
  36         lock_super(sb);
  37         if (sb->s_dirt && sb->s_op->write_super)
  38                 sb->s_op->write_super(sb);
  39         unlock_super(sb);
  40         if (sb->s_op->sync_fs)
  41                 sb->s_op->sync_fs(sb, wait);
  42         return __sync_blockdev(sb->s_bdev, wait);
  43 }
  44
  45 /*
  46  * Write out and wait upon all dirty data associated with this
  47  * superblock.  Filesystem data as well as the underlying block
  48  * device.  Takes the superblock lock.
  49  */
  50 int sync_filesystem(struct super_block *sb)
  51 {
  52         int ret;
  53
  54         /*
  55          * We need to be protected against the filesystem going from
  56          * r/o to r/w or vice versa.
  57          */
  58         WARN_ON(!rwsem_is_locked(&sb->s_umount));
  59
  60         /*
  61          * No point in syncing out anything if the filesystem is read-only.
  62          */
  63         if (sb->s_flags & MS_RDONLY)
  64                 return 0;
  65
  66         ret = __sync_filesystem(sb, 0);
  67         if (ret < 0)
  68                 return ret;
  69         return __sync_filesystem(sb, 1);
  70 }
  71 EXPORT_SYMBOL_GPL(sync_filesystem);
  72
  73 /*
  74  * Sync all the data for all the filesystems (called by sys_sync() and
  75  * emergency sync)
  76  *
  77  * This operation is careful to avoid the livelock which could easily happen
  78  * if two or more filesystems are being continuously dirtied.  s_need_sync
  79  * is used only here.  We set it against all filesystems and then clear it as
  80  * we sync them.  So redirtied filesystems are skipped.
  81  *
  82  * But if process A is currently running sync_filesystems and then process B
  83  * calls sync_filesystems as well, process B will set all the s_need_sync
  84  * flags again, which will cause process A to resync everything.  Fix that with
  85  * a local mutex.
  86  */
  87 static void sync_filesystems(int wait)
  88 {
  89         struct super_block *sb;
  90         static DEFINE_MUTEX(mutex);
  91
  92         mutex_lock(&mutex);             /* Could be down_interruptible */
  93         spin_lock(&sb_lock);
  94         list_for_each_entry(sb, &super_blocks, s_list)
  95                 sb->s_need_sync = 1;
  96
  97 restart:
  98         list_for_each_entry(sb, &super_blocks, s_list) {
  99                 if (!sb->s_need_sync)
 100                         continue;
 101                 sb->s_need_sync = 0;
 102                 sb->s_count++;
 103                 spin_unlock(&sb_lock);
 104
 105                 down_read(&sb->s_umount);
 106                 if (!(sb->s_flags & MS_RDONLY) && sb->s_root)
 107                         __sync_filesystem(sb, wait);
 108                 up_read(&sb->s_umount);
 109
 110                 /* restart only when sb is no longer on the list */
 111                 spin_lock(&sb_lock);
 112                 if (__put_super_and_need_restart(sb))
 113                         goto restart;
 114         }
 115         spin_unlock(&sb_lock);
 116         mutex_unlock(&mutex);
 117 }
 118
 119 SYSCALL_DEFINE0(sync)
 120 {
 121         sync_filesystems(0);
 122         sync_filesystems(1);
 123         if (unlikely(laptop_mode))
 124                 laptop_sync_completion();
 125         return 0;
 126 }
 127
 128 static void do_sync_work(struct work_struct *work)
 129 {
 130         /*
 131          * Sync twice to reduce the possibility we skipped some inodes / pages
 132          * because they were temporarily locked
 133          */
 134         sync_filesystems(0);
 135         sync_filesystems(0);
 136         printk("Emergency Sync complete\n");
 137         kfree(work);
 138 }
 139
 140 void emergency_sync(void)
 141 {
 142         struct work_struct *work;
 143
 144         work = kmalloc(sizeof(*work), GFP_ATOMIC);
 145         if (work) {
 146                 INIT_WORK(work, do_sync_work);
 147                 schedule_work(work);
 148         }
 149 }
 150
 151 /*
 152  * Generic function to fsync a file.
 153  *
 154  * filp may be NULL if called via the msync of a vma.
 155  */
 156 int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
 157 {
 158         struct inode * inode = dentry->d_inode;
 159         struct super_block * sb;
 160         int ret, err;
 161
 162         /* sync the inode to buffers */
 163         ret = write_inode_now(inode, 0);
 164
 165         /* sync the superblock to buffers */
 166         sb = inode->i_sb;
 167         lock_super(sb);
 168         if (sb->s_dirt && sb->s_op->write_super)
 169                 sb->s_op->write_super(sb);
 170         unlock_super(sb);
 171
 172         /* .. finally sync the buffers to disk */
 173         err = sync_blockdev(sb->s_bdev);
 174         if (!ret)
 175                 ret = err;
 176         return ret;
 177 }
 178
 179 /**
 180  * vfs_fsync - perform a fsync or fdatasync on a file
 181  * @file:               file to sync
 182  * @dentry:             dentry of @file
 183  * @data:               only perform a fdatasync operation
 184  *
 185  * Write back data and metadata for @file to disk.  If @datasync is
 186  * set only metadata needed to access modified file data is written.
 187  *
 188  * In case this function is called from nfsd @file may be %NULL and
 189  * only @dentry is set.  This can only happen when the filesystem
 190  * implements the export_operations API.
 191  */
 192 int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
 193 {
 194         const struct file_operations *fop;
 195         struct address_space *mapping;
 196         int err, ret;
 197
 198         /*
 199          * Get mapping and operations from the file in case we have
 200          * as file, or get the default values for them in case we
 201          * don't have a struct file available.  Damn nfsd..
 202          */
 203         if (file) {
 204                 mapping = file->f_mapping;
 205                 fop = file->f_op;
 206         } else {
 207                 mapping = dentry->d_inode->i_mapping;
 208                 fop = dentry->d_inode->i_fop;
 209         }
 210
 211         if (!fop || !fop->fsync) {
 212                 ret = -EINVAL;
 213                 goto out;
 214         }
 215
 216         ret = filemap_fdatawrite(mapping);
 217
 218         /*
 219          * We need to protect against concurrent writers, which could cause
 220          * livelocks in fsync_buffers_list().
 221          */
 222         mutex_lock(&mapping->host->i_mutex);
 223         err = fop->fsync(file, dentry, datasync);
 224         if (!ret)
 225                 ret = err;
 226         mutex_unlock(&mapping->host->i_mutex);
 227         err = filemap_fdatawait(mapping);
 228         if (!ret)
 229                 ret = err;
 230 out:
 231         return ret;
 232 }
 233 EXPORT_SYMBOL(vfs_fsync);
 234
 235 static int do_fsync(unsigned int fd, int datasync)
 236 {
 237         struct file *file;
 238         int ret = -EBADF;
 239
 240         file = fget(fd);
 241         if (file) {
 242                 ret = vfs_fsync(file, file->f_path.dentry, datasync);
 243                 fput(file);
 244         }
 245         return ret;
 246 }
 247
 248 SYSCALL_DEFINE1(fsync, unsigned int, fd)
 249 {
 250         return do_fsync(fd, 0);
 251 }
 252
 253 SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
 254 {
 255         return do_fsync(fd, 1);
 256 }
 257
 258 /*
 259  * sys_sync_file_range() permits finely controlled syncing over a segment of
 260  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
 261  * zero then sys_sync_file_range() will operate from offset out to EOF.
 262  *
 263  * The flag bits are:
 264  *
 265  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
 266  * before performing the write.
 267  *
 268  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
 269  * range which are not presently under writeback. Note that this may block for
 270  * significant periods due to exhaustion of disk request structures.
 271  *
 272  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
 273  * after performing the write.
 274  *
 275  * Useful combinations of the flag bits are:
 276  *
 277  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
 278  * in the range which were dirty on entry to sys_sync_file_range() are placed
 279  * under writeout.  This is a start-write-for-data-integrity operation.
 280  *
 281  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
 282  * are not presently under writeout.  This is an asynchronous flush-to-disk
 283  * operation.  Not suitable for data integrity operations.
 284  *
 285  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
 286  * completion of writeout of all pages in the range.  This will be used after an
 287  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
 288  * for that operation to complete and to return the result.
 289  *
 290  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
 291  * a traditional sync() operation.  This is a write-for-data-integrity operation
 292  * which will ensure that all pages in the range which were dirty on entry to
 293  * sys_sync_file_range() are committed to disk.
 294  *
 295  *
 296  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
 297  * I/O errors or ENOSPC conditions and will return those to the caller, after
 298  * clearing the EIO and ENOSPC flags in the address_space.
 299  *
 300  * It should be noted that none of these operations write out the file's
 301  * metadata.  So unless the application is strictly performing overwrites of
 302  * already-instantiated disk blocks, there are no guarantees here that the data
 303  * will be available after a crash.
 304  */
 305 SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
 306                                 unsigned int flags)
 307 {
 308         int ret;
 309         struct file *file;
 310         loff_t endbyte;                 /* inclusive */
 311         int fput_needed;
 312         umode_t i_mode;
 313
 314         ret = -EINVAL;
 315         if (flags & ~VALID_FLAGS)
 316                 goto out;
 317
 318         endbyte = offset + nbytes;
 319
 320         if ((s64)offset < 0)
 321                 goto out;
 322         if ((s64)endbyte < 0)
 323                 goto out;
 324         if (endbyte < offset)
 325                 goto out;
 326
 327         if (sizeof(pgoff_t) == 4) {
 328                 if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
 329                         /*
 330                          * The range starts outside a 32 bit machine's
 331                          * pagecache addressing capabilities.  Let it "succeed"
 332                          */
 333                         ret = 0;
 334                         goto out;
 335                 }
 336                 if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
 337                         /*
 338                          * Out to EOF
 339                          */
 340                         nbytes = 0;
 341                 }
 342         }
 343
 344         if (nbytes == 0)
 345                 endbyte = LLONG_MAX;
 346         else
 347                 endbyte--;              /* inclusive */
 348
 349         ret = -EBADF;
 350         file = fget_light(fd, &fput_needed);
 351         if (!file)
 352                 goto out;
 353
 354         i_mode = file->f_path.dentry->d_inode->i_mode;
 355         ret = -ESPIPE;
 356         if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
 357                         !S_ISLNK(i_mode))
 358                 goto out_put;
 359
 360         ret = do_sync_mapping_range(file->f_mapping, offset, endbyte, flags);
 361 out_put:
 362         fput_light(file, fput_needed);
 363 out:
 364         return ret;
 365 }
 366 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 367 asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
 368                                     long flags)
 369 {
 370         return SYSC_sync_file_range((int) fd, offset, nbytes,
 371                                     (unsigned int) flags);
 372 }
 373 SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
 374 #endif
 375
 376 /* It would be nice if people remember that not all the world's an i386
 377    when they introduce new system calls */
 378 SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
 379                                  loff_t offset, loff_t nbytes)
 380 {
 381         return sys_sync_file_range(fd, offset, nbytes, flags);
 382 }
 383 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 384 asmlinkage long SyS_sync_file_range2(long fd, long flags,
 385                                      loff_t offset, loff_t nbytes)
 386 {
 387         return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
 388                                      offset, nbytes);
 389 }
 390 SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
 391 #endif
 392
 393 /*
 394  * `endbyte' is inclusive
 395  */
 396 int do_sync_mapping_range(struct address_space *mapping, loff_t offset,
 397                           loff_t endbyte, unsigned int flags)
 398 {
 399         int ret;
 400
 401         if (!mapping) {
 402                 ret = -EINVAL;
 403                 goto out;
 404         }
 405
 406         ret = 0;
 407         if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
 408                 ret = wait_on_page_writeback_range(mapping,
 409                                         offset >> PAGE_CACHE_SHIFT,
 410                                         endbyte >> PAGE_CACHE_SHIFT);
 411                 if (ret < 0)
 412                         goto out;
 413         }
 414
 415         if (flags & SYNC_FILE_RANGE_WRITE) {
 416                 ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
 417                                                 WB_SYNC_ALL);
 418                 if (ret < 0)
 419                         goto out;
 420         }
 421
 422         if (flags & SYNC_FILE_RANGE_WAIT_AFTER) {
 423                 ret = wait_on_page_writeback_range(mapping,
 424                                         offset >> PAGE_CACHE_SHIFT,
 425                                         endbyte >> PAGE_CACHE_SHIFT);
 426         }
 427 out:
 428         return ret;
 429 }
 430 EXPORT_SYMBOL_GPL(do_sync_mapping_range);