From c15c54f5f056ee4819da9fde59a5f2cd45445f23 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Mon, 27 Apr 2009 16:43:52 +0200 Subject: vfs: Move syncing code from super.c to sync.c (version 4) Move sync_filesystems(), __fsync_super(), fsync_super() from super.c to sync.c where it fits better. [build fixes folded] Signed-off-by: Jan Kara Signed-off-by: Al Viro --- fs/sync.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) (limited to 'fs/sync.c') diff --git a/fs/sync.c b/fs/sync.c index be0798c..d5fa7b7 100644 --- a/fs/sync.c +++ b/fs/sync.c @@ -18,6 +18,91 @@ #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \ SYNC_FILE_RANGE_WAIT_AFTER) +/* + * Do the filesystem syncing work. For simple filesystems sync_inodes_sb(sb, 0) + * just dirties buffers with inodes so we have to submit IO for these buffers + * via __sync_blockdev(). This also speeds up the wait == 1 case since in that + * case write_inode() functions do sync_dirty_buffer() and thus effectively + * write one block at a time. + */ +static int __fsync_super(struct super_block *sb, int wait) +{ + vfs_dq_sync(sb); + sync_inodes_sb(sb, wait); + lock_super(sb); + if (sb->s_dirt && sb->s_op->write_super) + sb->s_op->write_super(sb); + unlock_super(sb); + if (sb->s_op->sync_fs) + sb->s_op->sync_fs(sb, wait); + return __sync_blockdev(sb->s_bdev, wait); +} + +/* + * Write out and wait upon all dirty data associated with this + * superblock. Filesystem data as well as the underlying block + * device. Takes the superblock lock. + */ +int fsync_super(struct super_block *sb) +{ + int ret; + + ret = __fsync_super(sb, 0); + if (ret < 0) + return ret; + return __fsync_super(sb, 1); +} +EXPORT_SYMBOL_GPL(fsync_super); + +/* + * Sync all the data for all the filesystems (called by sys_sync() and + * emergency sync) + * + * This operation is careful to avoid the livelock which could easily happen + * if two or more filesystems are being continuously dirtied. s_need_sync + * is used only here. We set it against all filesystems and then clear it as + * we sync them. So redirtied filesystems are skipped. + * + * But if process A is currently running sync_filesystems and then process B + * calls sync_filesystems as well, process B will set all the s_need_sync + * flags again, which will cause process A to resync everything. Fix that with + * a local mutex. + */ +static void sync_filesystems(int wait) +{ + struct super_block *sb; + static DEFINE_MUTEX(mutex); + + mutex_lock(&mutex); /* Could be down_interruptible */ + spin_lock(&sb_lock); + list_for_each_entry(sb, &super_blocks, s_list) { + if (sb->s_flags & MS_RDONLY) + continue; + sb->s_need_sync = 1; + } + +restart: + list_for_each_entry(sb, &super_blocks, s_list) { + if (!sb->s_need_sync) + continue; + sb->s_need_sync = 0; + if (sb->s_flags & MS_RDONLY) + continue; /* hm. Was remounted r/o meanwhile */ + sb->s_count++; + spin_unlock(&sb_lock); + down_read(&sb->s_umount); + if (sb->s_root) + __fsync_super(sb, wait); + up_read(&sb->s_umount); + /* restart only when sb is no longer on the list */ + spin_lock(&sb_lock); + if (__put_super_and_need_restart(sb)) + goto restart; + } + spin_unlock(&sb_lock); + mutex_unlock(&mutex); +} + SYSCALL_DEFINE0(sync) { sync_filesystems(0); -- cgit v1.1