Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754094AbcDVLLx (ORCPT ); Fri, 22 Apr 2016 07:11:53 -0400 Received: from mx2.suse.de ([195.135.220.15]:44217 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753780AbcDVLGe (ORCPT ); Fri, 22 Apr 2016 07:06:34 -0400 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Greg Thelen , David Rientjes , Andrew Morton , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 64/78] fs, seqfile: always allow oom killer Date: Fri, 22 Apr 2016 13:05:47 +0200 Message-Id: <8bb06e0975c2587f5acd9f714c53130dd1fb5ca4.1461323133.git.jslaby@suse.cz> X-Mailer: git-send-email 2.8.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2531 Lines: 66 From: Greg Thelen 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 0f930902eb8806cff8dcaef9ff9faf3cfa5fd748 upstream. Since 5cec38ac866b ("fs, seq_file: fallback to vmalloc instead of oom kill processes") seq_buf_alloc() avoids calling the oom killer for PAGE_SIZE or smaller allocations; but larger allocations can use the oom killer via vmalloc(). Thus reads of small files can return ENOMEM, but larger files use the oom killer to avoid ENOMEM. The effect of this bug is that reads from /proc and other virtual filesystems can return ENOMEM instead of the preferred behavior - oom killing something (possibly the calling process). I don't know of anyone except Google who has noticed the issue. I suspect the fix is more needed in smaller systems where there isn't any reclaimable memory. But these seem like the kinds of systems which probably don't use the oom killer for production situations. Memory overcommit requires use of the oom killer to select a victim regardless of file size. Enable oom killer for small seq_buf_alloc() allocations. Fixes: 5cec38ac866b ("fs, seq_file: fallback to vmalloc instead of oom kill processes") Signed-off-by: David Rientjes Signed-off-by: Greg Thelen Acked-by: Eric Dumazet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby --- fs/seq_file.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/seq_file.c b/fs/seq_file.c index 96ae14abce98..a3e41be17e5e 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -35,12 +35,17 @@ static void seq_set_overflow(struct seq_file *m) static void *seq_buf_alloc(unsigned long size) { void *buf; + gfp_t gfp = GFP_KERNEL; /* - * __GFP_NORETRY to avoid oom-killings with high-order allocations - - * it's better to fall back to vmalloc() than to kill things. + * For high order allocations, use __GFP_NORETRY to avoid oom-killing - + * it's better to fall back to vmalloc() than to kill things. For small + * allocations, just use GFP_KERNEL which will oom kill, thus no need + * for vmalloc fallback. */ - buf = kmalloc(size, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN); + if (size > PAGE_SIZE) + gfp |= __GFP_NORETRY | __GFP_NOWARN; + buf = kmalloc(size, gfp); if (!buf && size > PAGE_SIZE) buf = vmalloc(size); return buf; -- 2.8.1