vfs: fix unconditional write_super() call in file_fsync()

We need to check ->s_dirt before calling write_super().  It became the cause
of an unneeded write.

This bug was noticed by Sudhanshu Saxena.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/sync.c b/fs/sync.c
index 7cd005ea7639..228e17b5e9ee 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -64,7 +64,7 @@ int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
         /* sync the superblock to buffers */
         sb = inode->i_sb;
         lock_super(sb);
-        if (sb->s_op->write_super)
+        if (sb->s_dirt && sb->s_op->write_super)
                 sb->s_op->write_super(sb);
         unlock_super(sb);