From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Monakhov Subject: Re: [PATCH] ext4: fix potential deadlock in ext4_nonda_switch() Date: Thu, 27 Sep 2012 22:16:15 +0400 Message-ID: <87fw63ib68.fsf@openvz.org> References: <1348111390-23083-1-git-send-email-tytso@mit.edu> <505CE635.6060101@redhat.com> <20120921235912.GA27207@thunk.org> <87ipaziduh.fsf@openvz.org> <20120927180949.GA6862@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Sandeen , Ext4 Developers List , stable@vger.kernel.org To: Theodore Ts'o Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:58221 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754140Ab2I0SQS (ORCPT ); Thu, 27 Sep 2012 14:16:18 -0400 In-Reply-To: <20120927180949.GA6862@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, 27 Sep 2012 14:09:49 -0400, Theodore Ts'o wrote: > 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: I use b1725167c38ab current ext4.git/dev head. > "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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html