From patchwork Mon Sep 14 13:56:15 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pradeep P V K X-Patchwork-Id: 11773815 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4947D6CA for ; Mon, 14 Sep 2020 13:57:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 37B2320E65 for ; Mon, 14 Sep 2020 13:57:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726775AbgINN5m (ORCPT ); Mon, 14 Sep 2020 09:57:42 -0400 Received: from alexa-out.qualcomm.com ([129.46.98.28]:47608 "EHLO alexa-out.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726559AbgINN5G (ORCPT ); Mon, 14 Sep 2020 09:57:06 -0400 Received: from ironmsg09-lv.qualcomm.com ([10.47.202.153]) by alexa-out.qualcomm.com with ESMTP; 14 Sep 2020 06:56:32 -0700 Received: from ironmsg02-blr.qualcomm.com ([10.86.208.131]) by ironmsg09-lv.qualcomm.com with ESMTP/TLS/AES256-SHA; 14 Sep 2020 06:56:31 -0700 Received: from hydcbspbld03.qualcomm.com ([10.242.221.48]) by ironmsg02-blr.qualcomm.com with ESMTP; 14 Sep 2020 19:26:20 +0530 Received: by hydcbspbld03.qualcomm.com (Postfix, from userid 2304101) id DE05F20E86; Mon, 14 Sep 2020 19:26:18 +0530 (IST) From: Pradeep P V K To: miklos@szeredi.hu Cc: linux-fsdevel@vger.kernel.org, stummala@codeaurora.org, sayalil@codeaurora.org, Pradeep P V K Subject: [PATCH V1] fuse: Remove __GFP_FS flag to avoid allocator recursing Date: Mon, 14 Sep 2020 19:26:15 +0530 Message-Id: <1600091775-10639-1-git-send-email-ppvk@codeaurora.org> X-Mailer: git-send-email 2.7.4 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Found a deadlock between kswapd, writeback thread and fuse process Here are the sequence of events with callstacks on the deadlock. process#1 process#2 process#3 __switch_to+0x150 __switch_to+0x150 try_to_free_pages __schedule+0x984 __schedule+0x984 memalloc_noreclaim_restore schedule+0x70 schedule+0x70 __perform_reclaim bit_wait+0x14 __fuse_request_send+0x154 __alloc_pages_direct_reclaim __wait_on_bit+0x70 fuse_simple_request+0x174 inode_wait_for_writeback+0xa0 __alloc_pages_slowpath fuse_flush_times+0x10c evict+0xa4 fuse_write_inode+0x5c __alloc_pages_nodemask iput+0x248 __writeback_single_inode+0x3d4 dentry_unlink_inode+0xd8 __alloc_pages_node writeback_sb_inodes+0x4a0 __dentry_kill+0x160 __writeback_inodes_wb+0xac shrink_dentry_list+0x170 alloc_pages_node wb_writeback+0x26c fuse_copy_fill prune_dcache_sb+0x54 wb_workfn+0x2c0 fuse_copy_one super_cache_scan+0x114 process_one_work+0x278 fuse_read_single_forget do_shrink_slab+0x24c worker_thread+0x26c fuse_read_forget shrink_slab+0xa8 kthread+0x118 fuse_dev_do_read shrink_node+0x118 fuse_dev_splice_read kswapd+0x92c do_splice_to do_splice Process#1(kswapd) held an inode lock and initaited a writeback to free the pages, as the inode superblock is fuse, process#2 forms a fuse request. Process#3 (Fuse daemon threads) while serving process#2 request, it requires memory(pages) and as the system is already running in low memory it ends up in calling try_to_ free_pages(), which might now call kswapd again, which is already stuck with an inode lock held. Thus forms a deadlock. So, remove __GFP_FS flag to avoid allocator recursing into the filesystem that might already held locks. Signed-off-by: Pradeep P V K --- fs/fuse/dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 02b3c36..2859024 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -708,7 +708,7 @@ static int fuse_copy_fill(struct fuse_copy_state *cs) if (cs->nr_segs >= cs->pipe->max_usage) return -EIO; - page = alloc_page(GFP_HIGHUSER); + page = alloc_page(GFP_NOFS | __GFP_HARDWALL | __GFP_HIGHMEM); if (!page) return -ENOMEM;