From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755618AbbCRPpo (ORCPT ); Wed, 18 Mar 2015 11:45:44 -0400 Received: from cantor2.suse.de ([195.135.220.15]:35177 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750896AbbCRPpm (ORCPT ); Wed, 18 Mar 2015 11:45:42 -0400 Date: Wed, 18 Mar 2015 16:45:40 +0100 From: Michal Hocko To: Andrew Morton Cc: Al Viro , Johannes Weiner , Mel Gorman , Rik van Riel , Neil Brown , Tetsuo Handa , Sage Weil , Mark Fasheh , linux-mm@kvack.org, LKML Subject: Re: [PATCH] mm: Use GFP_KERNEL allocation for the page cache in page_cache_read Message-ID: <20150318154540.GN17241@dhcp22.suse.cz> References: <1426687766-518-1-git-send-email-mhocko@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1426687766-518-1-git-send-email-mhocko@suse.cz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org What do you think about this v2? I cannot say I would like it but I really dislike the whole mapping_gfp_mask API to be honest. --- >>From d88010d6f5f59d7eb87b691e27e201d12cab9141 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Wed, 18 Mar 2015 16:06:40 +0100 Subject: [PATCH] mm: Allow __GFP_FS for page_cache_read page cache allocation page_cache_read has been historically using page_cache_alloc_cold to allocate a new page. This means that mapping_gfp_mask is used as the base for the gfp_mask. Many filesystems are setting this mask to GFP_NOFS to prevent from fs recursion issues. page_cache_read is, however, not called from the fs layer so it doesn't need this protection. Even ceph and ocfs2 which call filemap_fault from their fault handlers seem to be OK because they are not taking any fs lock before invoking generic implementation. The protection might be even harmful. There is a strong push to fail GFP_NOFS allocations rather than loop within allocator indefinitely with a very limited reclaim ability. Once we start failing those requests the OOM killer might be triggered prematurely because the page cache allocation failure is propagated up the page fault path and end up in pagefault_out_of_memory. Add __GFP_FS and __GFPIO to the gfp mask which is coming from the mapping to fix this issue. Reported-by: Tetsuo Handa Signed-off-by: Michal Hocko --- mm/filemap.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index 968cd8e03d2e..8b50d5eb52b2 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1752,7 +1752,15 @@ static int page_cache_read(struct file *file, pgoff_t offset) int ret; do { - page = page_cache_alloc_cold(mapping); + gfp_t page_cache_gfp = mapping_gfp_mask(mapping)|__GFP_COLD; + + /* + * This code is not called from the fs layer so we do not need + * reclaim recursion protection. !GFP_FS might fail too easy + * and trigger OOM killer prematuraly. + */ + page_cache_gfp |= __GFP_FS | __GFP_IO; + page = __page_cache_alloc(page_cache_gfp); if (!page) return -ENOMEM; -- 2.1.4 -- Michal Hocko SUSE Labs