From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750773AbWG0JTI (ORCPT ); Thu, 27 Jul 2006 05:19:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750967AbWG0JTI (ORCPT ); Thu, 27 Jul 2006 05:19:08 -0400 Received: from smtp108.mail.mud.yahoo.com ([209.191.85.218]:56483 "HELO smtp108.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S1750773AbWG0JTH (ORCPT ); Thu, 27 Jul 2006 05:19:07 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=cgWOblKYqgn2ShsGZPXbG0gLkO+aFKKeRvAuGdAJNE1yihFxcRiTOCgBpMf3MNzAoa3shxy21mBWKkYxli1adm3Fmh3FGBDETZnFMbOsfnijN8esRRESYLzJpEdWPyuSE1CeI9s3bJbB14ENGpAYFsok2edoENasK8xVNapDd2M= ; Message-ID: <44C884EF.6010705@yahoo.com.au> Date: Thu, 27 Jul 2006 19:18:39 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Anton Altaparmakov CC: Andrew Morton , eike-kernel@sf-tec.de, linux-kernel@vger.kernel.org, aia21@cantab.net Subject: Re: [BUG?] possible recursive locking detected References: <200607261805.26711.eike-kernel@sf-tec.de> <20060726225311.f51cee6d.akpm@osdl.org> <44C86271.9030603@yahoo.com.au> <1153984527.21849.2.camel@imp.csi.cam.ac.uk> <20060727003806.def43f26.akpm@osdl.org> <1153988398.21849.16.camel@imp.csi.cam.ac.uk> In-Reply-To: <1153988398.21849.16.camel@imp.csi.cam.ac.uk> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Anton Altaparmakov wrote: > On Thu, 2006-07-27 at 00:38 -0700, Andrew Morton wrote: > >>On Thu, 27 Jul 2006 08:15:27 +0100 >>Anton Altaparmakov wrote: >> >> >>>>I'm surprised ext2 is allocating with __GFP_FS set, though. Would that >>>>cause any problem? >>> >>>That is an ext2 bug IMO. >> >>There is no bug. >> >>What there is is an ill-defined set of rules. If we want to tighten these >>rules we have a choice between > > > I beg to differ. It is a bug. You cannot reenter the file system when > the file system is trying to allocate memory. Otherwise you can never > allocate memory with any locks held or you are bound to introduce an > A->B B->A deadlock somewhere. I don't think it is a bug in general. It really depends on the allocation: - If it is a path that might be required in order to writeout a page, then yes GFP_NOFS is going to help prevent deadlocks. - If it is a path where you'll take the same locks as page reclaim requires, then again GFP_NOFS is required. For NTFS case, it seems like holding i_mutex on the write path falls foul of the second problem. But I agree with Andrew that this is a critical case where we do have to enter the fs. GFP_NOFS is too big a hammer to use. I guess you'd have to change NTFS to do something sane privately, or come up with a nice general solution that doesn't harm the common filesystems that apparently don't have a problem here... can you just add GFP_NOFS to NTFS's mapping_gfp_mask to start with? -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com