From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8C1DDECE587 for ; Tue, 1 Oct 2019 18:11:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A70A2133F for ; Tue, 1 Oct 2019 18:11:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731408AbfJASLZ (ORCPT ); Tue, 1 Oct 2019 14:11:25 -0400 Received: from mx2.suse.de ([195.135.220.15]:37276 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727345AbfJASLZ (ORCPT ); Tue, 1 Oct 2019 14:11:25 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 84D8FAE6D; Tue, 1 Oct 2019 18:11:23 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 2A233DA88C; Tue, 1 Oct 2019 20:11:41 +0200 (CEST) Date: Tue, 1 Oct 2019 20:11:41 +0200 From: David Sterba To: Josef Bacik Cc: kernel-team@fb.com, linux-btrfs@vger.kernel.org, Zdenek Sojka Subject: Re: [PATCH] btrfs: nofs inode allocations Message-ID: <20191001181141.GG2751@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Josef Bacik , kernel-team@fb.com, linux-btrfs@vger.kernel.org, Zdenek Sojka References: <20190909141204.24557-1-josef@toxicpanda.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190909141204.24557-1-josef@toxicpanda.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Sep 09, 2019 at 10:12:04AM -0400, Josef Bacik wrote: > A user reported a lockdep splat > > ====================================================== > WARNING: possible circular locking dependency detected > 5.2.11-gentoo #2 Not tainted > ------------------------------------------------------ > kswapd0/711 is trying to acquire lock: > 000000007777a663 (sb_internal){.+.+}, at: start_transaction+0x3a8/0x500 > > but task is already holding lock: > 000000000ba86300 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #1 (fs_reclaim){+.+.}: > kmem_cache_alloc+0x1f/0x1c0 > btrfs_alloc_inode+0x1f/0x260 > alloc_inode+0x16/0xa0 > new_inode+0xe/0xb0 > btrfs_new_inode+0x70/0x610 > btrfs_symlink+0xd0/0x420 > vfs_symlink+0x9c/0x100 > do_symlinkat+0x66/0xe0 > do_syscall_64+0x55/0x1c0 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > -> #0 (sb_internal){.+.+}: > __sb_start_write+0xf6/0x150 > start_transaction+0x3a8/0x500 > btrfs_commit_inode_delayed_inode+0x59/0x110 > btrfs_evict_inode+0x19e/0x4c0 > evict+0xbc/0x1f0 > inode_lru_isolate+0x113/0x190 > __list_lru_walk_one.isra.4+0x5c/0x100 > list_lru_walk_one+0x32/0x50 > prune_icache_sb+0x36/0x80 > super_cache_scan+0x14a/0x1d0 > do_shrink_slab+0x131/0x320 > shrink_node+0xf7/0x380 > balance_pgdat+0x2d5/0x640 > kswapd+0x2ba/0x5e0 > kthread+0x147/0x160 > ret_from_fork+0x24/0x30 > > other info that might help us debug this: > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(fs_reclaim); > lock(sb_internal); > lock(fs_reclaim); > lock(sb_internal); > *** DEADLOCK *** > > 3 locks held by kswapd0/711: > #0: 000000000ba86300 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 > #1: 000000004a5100f8 (shrinker_rwsem){++++}, at: shrink_node+0x9a/0x380 > #2: 00000000f956fa46 (&type->s_umount_key#30){++++}, at: super_cache_scan+0x35/0x1d0 > > stack backtrace: > CPU: 7 PID: 711 Comm: kswapd0 Not tainted 5.2.11-gentoo #2 > Hardware name: Dell Inc. Precision Tower 3620/0MWYPT, BIOS 2.4.2 09/29/2017 > Call Trace: > dump_stack+0x85/0xc7 > print_circular_bug.cold.40+0x1d9/0x235 > __lock_acquire+0x18b1/0x1f00 > lock_acquire+0xa6/0x170 > ? start_transaction+0x3a8/0x500 > __sb_start_write+0xf6/0x150 > ? start_transaction+0x3a8/0x500 > start_transaction+0x3a8/0x500 > btrfs_commit_inode_delayed_inode+0x59/0x110 > btrfs_evict_inode+0x19e/0x4c0 > ? var_wake_function+0x20/0x20 > evict+0xbc/0x1f0 > inode_lru_isolate+0x113/0x190 > ? discard_new_inode+0xc0/0xc0 > __list_lru_walk_one.isra.4+0x5c/0x100 > ? discard_new_inode+0xc0/0xc0 > list_lru_walk_one+0x32/0x50 > prune_icache_sb+0x36/0x80 > super_cache_scan+0x14a/0x1d0 > do_shrink_slab+0x131/0x320 > shrink_node+0xf7/0x380 > balance_pgdat+0x2d5/0x640 > kswapd+0x2ba/0x5e0 > ? __wake_up_common_lock+0x90/0x90 > kthread+0x147/0x160 > ? balance_pgdat+0x640/0x640 > ? __kthread_create_on_node+0x160/0x160 > ret_from_fork+0x24/0x30 > > This is because btrfs_new_inode() calls new_inode() under the > transaction. We could probably move the new_inode() outside of this but > for now just wrap it in memalloc_nofs_save(). > > Reported-by: Zdenek Sojka > Signed-off-by: Josef Bacik Added to 5.4 queue, with the type fixed and updated subject.