From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756484Ab3JHU60 (ORCPT ); Tue, 8 Oct 2013 16:58:26 -0400 Received: from zene.cmpxchg.org ([85.214.230.12]:56667 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754227Ab3JHU6X (ORCPT ); Tue, 8 Oct 2013 16:58:23 -0400 From: Johannes Weiner To: Andrew Morton Cc: Michal Hocko , azurIt , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [patch 2/2] fs: buffer: move allocation failure loop into the allocator Date: Tue, 8 Oct 2013 16:58:10 -0400 Message-Id: <1381265890-11333-2-git-send-email-hannes@cmpxchg.org> X-Mailer: git-send-email 1.8.4 In-Reply-To: <1381265890-11333-1-git-send-email-hannes@cmpxchg.org> References: <1381265890-11333-1-git-send-email-hannes@cmpxchg.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Buffer allocation has a very crude indefinite loop around waking the flusher threads and performing global NOFS direct reclaim because it can not handle allocation failures. The most immediate problem with this is that the allocation may fail due to a memory cgroup limit, where flushers + direct reclaim might not make any progress towards resolving the situation at all. Because unlike the global case, a memory cgroup may not have any cache at all, only anonymous pages but no swap. This situation will lead to a reclaim livelock with insane IO from waking the flushers and thrashing unrelated filesystem cache in a tight loop. Use __GFP_NOFAIL allocations for buffers for now. This makes sure that any looping happens in the page allocator, which knows how to orchestrate kswapd, direct reclaim, and the flushers sensibly. It also allows memory cgroups to detect allocations that can't handle failure and will allow them to ultimately bypass the limit if reclaim can not make progress. Reported-by: azurIt Signed-off-by: Johannes Weiner Cc: stable@kernel.org --- fs/buffer.c | 14 ++++++++++++-- mm/memcontrol.c | 2 ++ 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index 4d74335..6024877 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1005,9 +1005,19 @@ grow_dev_page(struct block_device *bdev, sector_t block, struct buffer_head *bh; sector_t end_block; int ret = 0; /* Will call free_more_memory() */ + gfp_t gfp_mask; - page = find_or_create_page(inode->i_mapping, index, - (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); + gfp_mask = mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS; + gfp_mask |= __GFP_MOVABLE; + /* + * XXX: __getblk_slow() can not really deal with failure and + * will endlessly loop on improvised global reclaim. Prefer + * looping in the allocator rather than here, at least that + * code knows what it's doing. + */ + gfp_mask |= __GFP_NOFAIL; + + page = find_or_create_page(inode->i_mapping, index, gfp_mask); if (!page) return ret; diff --git a/mm/memcontrol.c b/mm/memcontrol.c index b39dfac..e233aa1 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2764,6 +2764,8 @@ done: return 0; nomem: *ptr = NULL; + if (gfp_mask & __GFP_NOFAIL) + return 0; return -ENOMEM; bypass: *ptr = root_mem_cgroup; -- 1.8.4