From 580be0837a7a59b207c3d5c661d044d8dd0a6a30 Mon Sep 17 00:00:00 2001 From: Jan Kara <jack@suse.cz> Date: Mon, 21 Sep 2009 17:01:06 -0700 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. [akpm@linux-foundation.org: add some commentary] Signed-off-by: Jan Kara <jack@suse.cz> Cc: Christoph Hellwig <hch@infradead.org> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> --- fs/inode.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/fs/inode.c b/fs/inode.c index b2ba83d2c4e1..798052f87035 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -695,13 +695,15 @@ void unlock_new_inode(struct inode *inode) } #endif /* - * This is special! We do not need the spinlock - * when clearing I_LOCK, because we're guaranteed - * that nobody else tries to do anything about the - * state of the inode when it is locked, as we - * just created it (so there can be no old holders - * that haven't tested I_LOCK). + * This is special! We do not need the spinlock when clearing I_LOCK, + * because we're guaranteed that nobody else tries to do anything about + * the state of the inode when it is locked, as we just created it (so + * there can be no old holders that haven't tested I_LOCK). + * However we must emit the memory barrier so that other CPUs reliably + * see the clearing of I_LOCK after the other inode initialisation has + * completed. */ + 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); -- GitLab