From: Theodore Ts'o <tytso@mit.edu>
To: Dmitry Monakhov <dmonakhov@openvz.org>
Cc: Eric Sandeen <sandeen@redhat.com>,
Ext4 Developers List <linux-ext4@vger.kernel.org>,
stable@vger.kernel.org
Subject: Re: [PATCH] ext4: fix potential deadlock in ext4_nonda_switch()
Date: Thu, 27 Sep 2012 16:14:01 -0400 [thread overview]
Message-ID: <20120927201401.GA9585@thunk.org> (raw)
In-Reply-To: <87fw63ib68.fsf@openvz.org>
Ah, you're right. I *can* easily see the problem; somehow I just
didn't notice it, but when I look back at my test logs, it's
definitely there. I thought sb_start_write() took s_umount, but it
doesn't, because it was trying to solve the exact same lock ordering
problem. Drat....
Unfortunately, there doesn't seem to be a good solution here. The two
options I see is either (a) create another version of
writeback_inodes_sb() which doesn't have the WARN_ON check in
fs/fs-writeback.c (the warning is a false positive, since there are
other mechanisms which protect the superblock from being unmounted
while the write system call is in progress), or (b) call
writeback_inodes_sb() out of a workqueue.
- Ted
prev parent reply other threads:[~2012-09-27 20:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-20 3:23 [PATCH] ext4: fix potential deadlock in ext4_nonda_switch() Theodore Ts'o
2012-09-21 22:12 ` Eric Sandeen
2012-09-21 23:59 ` Theodore Ts'o
2012-09-27 17:18 ` Dmitry Monakhov
2012-09-27 18:09 ` Theodore Ts'o
2012-09-27 18:16 ` Dmitry Monakhov
2012-09-27 20:14 ` Theodore Ts'o [this message]
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