vfs: Reorder operations during sys_sync

Change the order of operations during sync from

for_each_sb {
        writeback_inodes_sb();
        sync_fs(nowait);
        __sync_blockdev(nowait);
}
for_each_sb {
        sync_inodes_sb();
        sync_fs(wait);
        __sync_blockdev(wait);
}

to

for_each_sb
        writeback_inodes_sb();
for_each_sb
        sync_fs(nowait);
for_each_sb
        __sync_blockdev(nowait);
for_each_sb
        sync_inodes_sb();
for_each_sb
        sync_fs(wait);
for_each_sb
        __sync_blockdev(wait);

This is a preparation for the following patches in this series.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/sync.c b/fs/sync.c
index 66acd2b..490e902 100644 (file)
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -67,18 +67,28 @@ int sync_filesystem(struct super_block *sb)
 }
 EXPORT_SYMBOL_GPL(sync_filesystem);
 
-static void sync_one_sb(struct super_block *sb, void *arg)
+static void sync_inodes_one_sb(struct super_block *sb, void *arg)
 {
        if (!(sb->s_flags & MS_RDONLY))
-               __sync_filesystem(sb, *(int *)arg);
+               sync_inodes_sb(sb);
 }
-/*
- * Sync all the data for all the filesystems (called by sys_sync() and
- * emergency sync)
- */
-static void sync_filesystems(int wait)
+
+static void writeback_inodes_one_sb(struct super_block *sb, void *arg)
 {
-       iterate_supers(sync_one_sb, &wait);
+       if (!(sb->s_flags & MS_RDONLY))
+               writeback_inodes_sb(sb, WB_REASON_SYNC);
+}
+
+static void sync_fs_one_sb(struct super_block *sb, void *arg)
+{
+       if (!(sb->s_flags & MS_RDONLY) && sb->s_op->sync_fs)
+               sb->s_op->sync_fs(sb, *(int *)arg);
+}
+
+static void sync_blkdev_one_sb(struct super_block *sb, void *arg)
+{
+       if (!(sb->s_flags & MS_RDONLY))
+               __sync_blockdev(sb->s_bdev, *(int *)arg);
 }
 
 /*
@@ -87,9 +97,15 @@ static void sync_filesystems(int wait)
  */
 SYSCALL_DEFINE0(sync)
 {
+       int nowait = 0, wait = 1;
+
        wakeup_flusher_threads(0, WB_REASON_SYNC);
-       sync_filesystems(0);
-       sync_filesystems(1);
+       iterate_supers(writeback_inodes_one_sb, NULL);
+       iterate_supers(sync_fs_one_sb, &nowait);
+       iterate_supers(sync_blkdev_one_sb, &nowait);
+       iterate_supers(sync_inodes_one_sb, NULL);
+       iterate_supers(sync_fs_one_sb, &wait);
+       iterate_supers(sync_blkdev_one_sb, &wait);
        if (unlikely(laptop_mode))
                laptop_sync_completion();
        return 0;
@@ -97,12 +113,18 @@ SYSCALL_DEFINE0(sync)
 
 static void do_sync_work(struct work_struct *work)
 {
+       int nowait = 0;
+
        /*
         * Sync twice to reduce the possibility we skipped some inodes / pages
         * because they were temporarily locked
         */
-       sync_filesystems(0);
-       sync_filesystems(0);
+       iterate_supers(sync_inodes_one_sb, &nowait);
+       iterate_supers(sync_fs_one_sb, &nowait);
+       iterate_supers(sync_blkdev_one_sb, &nowait);
+       iterate_supers(sync_inodes_one_sb, &nowait);
+       iterate_supers(sync_fs_one_sb, &nowait);
+       iterate_supers(sync_blkdev_one_sb, &nowait);
        printk("Emergency Sync complete\n");
        kfree(work);
 }