linux-kernel - [PATCH] fs: Make sure data stored into inode is properly seen before unlocking new inode

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Date:	Tue,  8 Sep 2009 13:41:03 +0200
From:	Jan Kara <jack@...e.cz>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	linux-fsdevel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>, hch@...radead.org,
	Jan Kara <jack@...e.cz>
Subject: [PATCH] fs: Make sure data stored into inode is properly seen before unlocking new inode

In theory it could happen that on one CPU we initialize a new inode but clearing
of I_NEW | I_LOCK gets reordered before some of the initialization. Thus on
another CPU we return not fully uptodate inode from iget_locked().

This seems to fix a corruption issue on ext3 mounted over NFS.

Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/inode.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

  Since Al doesn't seem to be online, does anybody else have opinion on this
patch? I can merge it via my tree but I'd like to get a review from someone
else.

diff --git a/fs/inode.c b/fs/inode.c
index 901bad1..e9a8e77 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -696,6 +696,7 @@ void unlock_new_inode(struct inode *inode)
 	 * just created it (so there can be no old holders
 	 * that haven't tested I_LOCK).
 	 */
+	smp_mb();
 	WARN_ON((inode->i_state & (I_LOCK|I_NEW)) != (I_LOCK|I_NEW));
 	inode->i_state &= ~(I_LOCK|I_NEW);
 	wake_up_inode(inode);
-- 
1.6.0.2

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