From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [RFC 0/2] mapping_gfp_mask from the page fault path Date: Tue, 2 Jun 2015 13:22:41 -0700 Message-ID: <20150602132241.26fbbc98be71920da8485b73@linux-foundation.org> References: <1433163603-13229-1-git-send-email-mhocko@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: , Dave Chinner , Neil Brown , Johannes Weiner , Al Viro , Mel Gorman , Rik van Riel , Tetsuo Handa , LKML , linux-fsdevel@vger.kernel.org To: Michal Hocko Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:45318 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751360AbbFBUWn (ORCPT ); Tue, 2 Jun 2015 16:22:43 -0400 In-Reply-To: <1433163603-13229-1-git-send-email-mhocko@suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, 1 Jun 2015 15:00:01 +0200 Michal Hocko wrote: > I somehow forgot about these patches. The previous version was > posted here: http://marc.info/?l=linux-mm&m=142668784122763&w=2. The > first attempt was broken but even when fixed it seems like ignoring > mapping_gfp_mask in page_cache_read is too fragile because > filesystems might use locks in their filemap_fault handlers > which could trigger recursion problems as pointed out by Dave > http://marc.info/?l=linux-mm&m=142682332032293&w=2. > > The first patch should be straightforward fix to obey mapping_gfp_mask > when allocating for mapping. It can be applied even without the second > one. I'm not so sure about that. If only [1/2] is applied then those filesystems which are setting mapping_gfp_mask to GFP_NOFS will now actually start using GFP_NOFS from within page_cache_read() etc. The weaker allocation mode might cause problems.