From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f44.google.com (mail-pa0-f44.google.com [209.85.220.44]) by kanga.kvack.org (Postfix) with ESMTP id A7FBA6B0038 for ; Sun, 23 Aug 2015 03:21:54 -0400 (EDT) Received: by pawq9 with SMTP id q9so81798857paw.3 for ; Sun, 23 Aug 2015 00:21:54 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id b6si21499565pdp.20.2015.08.23.00.21.53 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Sun, 23 Aug 2015 00:21:53 -0700 (PDT) Subject: [REPOST] [PATCH 1/2] mm: Fix race between setting TIF_MEMDIE and __alloc_pages_high_priority(). From: Tetsuo Handa Message-Id: <201508231621.EGJ17658.FFQJtFSLVOOHMO@I-love.SAKURA.ne.jp> Date: Sun, 23 Aug 2015 16:21:41 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@kernel.org, rientjes@google.com, hannes@cmpxchg.org Cc: linux-mm@kvack.org >>From 4a3cf5be07a66cf3906a380e77ba5e2ac1b2b3d5 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Sat, 1 Aug 2015 22:39:30 +0900 Subject: [PATCH 1/2] mm: Fix race between setting TIF_MEMDIE and __alloc_pages_high_priority(). Currently, TIF_MEMDIE is checked at gfp_to_alloc_flags() which is before calling __alloc_pages_high_priority() and at /* Avoid allocations with no watermarks from looping endlessly */ if (test_thread_flag(TIF_MEMDIE) && !(gfp_mask & __GFP_NOFAIL)) which is after returning from __alloc_pages_high_priority(). This means that if TIF_MEMDIE is set between returning from gfp_to_alloc_flags() and checking test_thread_flag(TIF_MEMDIE), the allocation can fail without calling __alloc_pages_high_priority(). We need to replace "test_thread_flag(TIF_MEMDIE)" with "whether TIF_MEMDIE was already set as of calling gfp_to_alloc_flags()" in order to close this race window. Since gfp_to_alloc_flags() includes ALLOC_NO_WATERMARKS for several cases, it will be more correct to replace "test_thread_flag(TIF_MEMDIE)" with "whether gfp_to_alloc_flags() included ALLOC_NO_WATERMARKS" because the purpose of test_thread_flag(TIF_MEMDIE) is to give up immediately if __alloc_pages_high_priority() failed. Note that we could simply do if (alloc_flags & ALLOC_NO_WATERMARKS) { ac->zonelist = node_zonelist(numa_node_id(), gfp_mask); page = __alloc_pages_high_priority(gfp_mask, order, ac); if (page) goto got_pg; WARN_ON_ONCE(!wait && (gfp_mask & __GFP_NOFAIL)); goto nopage; } instead of changing to if ((alloc_flags & ALLOC_NO_WATERMARKS) && !(gfp_mask & __GFP_NOFAIL)) goto nopage; if we can duplicate if (!wait) { WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL); goto nopage; } . Signed-off-by: Tetsuo Handa --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4b220cb..37a0390 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3085,7 +3085,7 @@ retry: goto nopage; /* Avoid allocations with no watermarks from looping endlessly */ - if (test_thread_flag(TIF_MEMDIE) && !(gfp_mask & __GFP_NOFAIL)) + if ((alloc_flags & ALLOC_NO_WATERMARKS) && !(gfp_mask & __GFP_NOFAIL)) goto nopage; /* -- 1.8.3.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org