From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Date: Tue, 29 Apr 2008 07:59:42 +0000 (-0700)
Subject: vfs: fix unconditional write_super() call in file_fsync()
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=762873c251b056c6c1b29e83a4dabafb064e5421;p=openwrt%2Fstaging%2Fblogic.git

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>
---

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);