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 14:09:49 -0400 [thread overview]
Message-ID: <20120927180949.GA6862@thunk.org> (raw)
In-Reply-To: <87ipaziduh.fsf@openvz.org>
On Thu, Sep 27, 2012 at 09:18:30PM +0400, Dmitry Monakhov wrote:
> Hmm... even this '!' patch is still not good. I've got that complain
> WARNING: at fs/fs-writeback.c:1316 writeback_inodes_sb_nr+0x1a3/0x200()
This WARN_ON checking to make sure the s_umount mutex is grabbed.
What kernel are you applying this patch against? Commit 14da92001:
"fs: Protect write paths by sb_start_write - sb_end_write" adds a call
to sb_start_write() in generic_file_aio_write() which means by the
time we call ext4_nonda_switch(), s_umount is grabbed, which probably
explains why I'm not seeing this --- 14da92001 was added to mainline
as of 3.6-rc1, and I'm guessing you're using an older kernel?
This is something we need to consider, though, since "ext4: fix
potential deadlock in ext4_nonda_switch()" is currently marked for
stable, but commit 14da92001 is not marked for stable. So if this
commit gets backported w/o 14da92001, stable kernel users will see
this warning.
- Ted
next prev parent reply other threads:[~2012-09-27 18:09 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 [this message]
2012-09-27 18:16 ` Dmitry Monakhov
2012-09-27 20:14 ` Theodore Ts'o
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