From patchwork Mon Jun 19 16:21:47 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Filipe Manana X-Patchwork-Id: 13284805 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE23FEB64DA for ; Mon, 19 Jun 2023 16:22:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231846AbjFSQWB (ORCPT ); Mon, 19 Jun 2023 12:22:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229448AbjFSQWA (ORCPT ); Mon, 19 Jun 2023 12:22:00 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2874DE5C for ; Mon, 19 Jun 2023 09:21:59 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B18FB60CEC for ; Mon, 19 Jun 2023 16:21:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9C5D5C433C9 for ; Mon, 19 Jun 2023 16:21:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1687191718; bh=b4FRC1CrWDiG+P0AmSwVkk2JbD/fLzpFs+31aQViJ/Q=; h=From:To:Subject:Date:In-Reply-To:References:From; b=YrFoAnXiPCtFiC3ONdB5c2WAxYxSufaapaz/SC3489AR7SKhM7P717X+rI8GXrwpQ 1P8njTBmC8IV809qeP0+HL9r/C+F5eOIxOYiXhSCFN0NFsowHe4Gm8Pe6rFofh0rjO mbsdJw3Jh2Y7c8pEDRY4e/+h+sYwGPYb11BvRuaLj1WqgiOYqbuJUVm5BeI2kL8aHv 5xUmKtvOP6Fcdvkr0GJ2CoqUN5m+GtNR8MSHszjS4k4shsb/UNTD7ZGwTA11iH+wTR BmByeeqzhxUFregPwchcghiv/bogBh8en2SNFzMZj/3N4sFWpDxsd2c7WOd3Tr0iQU EN+kYhVN+utUw== From: fdmanana@kernel.org To: linux-btrfs@vger.kernel.org Subject: [PATCH 1/4] btrfs: fix race when deleting quota root from the dirty cow roots list Date: Mon, 19 Jun 2023 17:21:47 +0100 Message-Id: X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Filipe Manana When disabling quotas we are deleting the quota root from the list fs_info->dirty_cowonly_roots without taking the lock that protects it, which is struct btrfs_fs_info::trans_lock. This unsynchronized list manipulation may cause chaos if there's another concurrent manipulation of this list, such as when adding a root to it with ctree.c:add_root_to_dirty_list(). This can result in all sorts of weird failures caused by a race, such as the following crash: [337571.278245] general protection fault, probably for non-canonical address 0xdead000000000108: 0000 [#1] PREEMPT SMP PTI [337571.278933] CPU: 1 PID: 115447 Comm: btrfs Tainted: G W 6.4.0-rc6-btrfs-next-134+ #1 [337571.279153] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 [337571.279572] RIP: 0010:commit_cowonly_roots+0x11f/0x250 [btrfs] [337571.279928] Code: 85 38 06 00 (...) [337571.280363] RSP: 0018:ffff9f63446efba0 EFLAGS: 00010206 [337571.280582] RAX: ffff942d98ec2638 RBX: ffff9430b82b4c30 RCX: 0000000449e1c000 [337571.280798] RDX: dead000000000100 RSI: ffff9430021e4900 RDI: 0000000000036070 [337571.281015] RBP: ffff942d98ec2000 R08: ffff942d98ec2000 R09: 000000000000015b [337571.281254] R10: 0000000000000009 R11: 0000000000000001 R12: ffff942fe8fbf600 [337571.281476] R13: ffff942dabe23040 R14: ffff942dabe20800 R15: ffff942d92cf3b48 [337571.281723] FS: 00007f478adb7340(0000) GS:ffff94349fa40000(0000) knlGS:0000000000000000 [337571.281950] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [337571.282184] CR2: 00007f478ab9a3d5 CR3: 000000001e02c001 CR4: 0000000000370ee0 [337571.282416] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [337571.282647] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [337571.282874] Call Trace: [337571.283101] [337571.283327] ? __die_body+0x1b/0x60 [337571.283570] ? die_addr+0x39/0x60 [337571.283796] ? exc_general_protection+0x22e/0x430 [337571.284022] ? asm_exc_general_protection+0x22/0x30 [337571.284251] ? commit_cowonly_roots+0x11f/0x250 [btrfs] [337571.284531] btrfs_commit_transaction+0x42e/0xf90 [btrfs] [337571.284803] ? _raw_spin_unlock+0x15/0x30 [337571.285031] ? release_extent_buffer+0x103/0x130 [btrfs] [337571.285305] reset_balance_state+0x152/0x1b0 [btrfs] [337571.285578] btrfs_balance+0xa50/0x11e0 [btrfs] [337571.285864] ? __kmem_cache_alloc_node+0x14a/0x410 [337571.286086] btrfs_ioctl+0x249a/0x3320 [btrfs] [337571.286358] ? mod_objcg_state+0xd2/0x360 [337571.286577] ? refill_obj_stock+0xb0/0x160 [337571.286798] ? seq_release+0x25/0x30 [337571.287016] ? __rseq_handle_notify_resume+0x3ba/0x4b0 [337571.287235] ? percpu_counter_add_batch+0x2e/0xa0 [337571.287455] ? __x64_sys_ioctl+0x88/0xc0 [337571.287675] __x64_sys_ioctl+0x88/0xc0 [337571.287901] do_syscall_64+0x38/0x90 [337571.288126] entry_SYSCALL_64_after_hwframe+0x72/0xdc [337571.288352] RIP: 0033:0x7f478aaffe9b So fix this by locking struct btrfs_fs_info::trans_lock before deleting the quota root from that list. Fixes: bed92eae26cc ("Btrfs: qgroup implementation and prototypes") Signed-off-by: Filipe Manana --- fs/btrfs/qgroup.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index f41da7ac360d..f8735b31da16 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1301,7 +1301,9 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info) goto out; } + spin_lock(&fs_info->trans_lock); list_del("a_root->dirty_list); + spin_unlock(&fs_info->trans_lock); btrfs_tree_lock(quota_root->node); btrfs_clear_buffer_dirty(trans, quota_root->node); From patchwork Mon Jun 19 16:21:48 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Filipe Manana X-Patchwork-Id: 13284806 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A94F7EB64DB for ; Mon, 19 Jun 2023 16:22:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231851AbjFSQWC (ORCPT ); Mon, 19 Jun 2023 12:22:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231370AbjFSQWB (ORCPT ); Mon, 19 Jun 2023 12:22:01 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 19E63E63 for ; Mon, 19 Jun 2023 09:22:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A375260D37 for ; Mon, 19 Jun 2023 16:21:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8E0E8C433C8 for ; Mon, 19 Jun 2023 16:21:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1687191719; bh=FQFnvuoaoV+n+wO9CXcURGW+tbO3m8y6YRtVi0XJ2ks=; h=From:To:Subject:Date:In-Reply-To:References:From; b=GFDDCkoJVj6gJwfKEWaFihiWIU9drf2+W9eKB6uc6BX4PWbbFSk6Tg1/inp6TM1eH zASqMec3iyDFxRleZvBaUkA6izlCtZPq3qGT0o68iv9LX8LreGEPWwd1kUBlPR9q2z VfLc0eGkysI4Hoz9r/EihNPB8hCMAP4kLRjN3BwrUu0EKLtiU4qkM+uOr9gaeOVVir yeIRhlbKx/pJlURfaTRifHOZC7ciywZl9Il38qVmHIRYv3vD386z9sFTHZiYuVe0Xd 8L70cHKmd/NE1+vzMVd9mJV0kizcb6FeUsQM59X7Lg19ED4dB3Rxj1rIKa07akHY7g gRdyDhWkjAccA== From: fdmanana@kernel.org To: linux-btrfs@vger.kernel.org Subject: [PATCH 2/4] btrfs: fix race when deleting free space root from the dirty cow roots list Date: Mon, 19 Jun 2023 17:21:48 +0100 Message-Id: X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Filipe Manana When deleting the free space tree we are deleting the free space root from the list fs_info->dirty_cowonly_roots without taking the lock that protects it, which is struct btrfs_fs_info::trans_lock. This unsynchronized list manipulation may cause chaos if there's another concurrent manipulation of this list, such as when adding a root to it with ctree.c:add_root_to_dirty_list(). This can result in all sorts of weird failures caused by a race, such as the following crash: [337571.278245] general protection fault, probably for non-canonical address 0xdead000000000108: 0000 [#1] PREEMPT SMP PTI [337571.278933] CPU: 1 PID: 115447 Comm: btrfs Tainted: G W 6.4.0-rc6-btrfs-next-134+ #1 [337571.279153] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 [337571.279572] RIP: 0010:commit_cowonly_roots+0x11f/0x250 [btrfs] [337571.279928] Code: 85 38 06 00 (...) [337571.280363] RSP: 0018:ffff9f63446efba0 EFLAGS: 00010206 [337571.280582] RAX: ffff942d98ec2638 RBX: ffff9430b82b4c30 RCX: 0000000449e1c000 [337571.280798] RDX: dead000000000100 RSI: ffff9430021e4900 RDI: 0000000000036070 [337571.281015] RBP: ffff942d98ec2000 R08: ffff942d98ec2000 R09: 000000000000015b [337571.281254] R10: 0000000000000009 R11: 0000000000000001 R12: ffff942fe8fbf600 [337571.281476] R13: ffff942dabe23040 R14: ffff942dabe20800 R15: ffff942d92cf3b48 [337571.281723] FS: 00007f478adb7340(0000) GS:ffff94349fa40000(0000) knlGS:0000000000000000 [337571.281950] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [337571.282184] CR2: 00007f478ab9a3d5 CR3: 000000001e02c001 CR4: 0000000000370ee0 [337571.282416] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [337571.282647] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [337571.282874] Call Trace: [337571.283101] [337571.283327] ? __die_body+0x1b/0x60 [337571.283570] ? die_addr+0x39/0x60 [337571.283796] ? exc_general_protection+0x22e/0x430 [337571.284022] ? asm_exc_general_protection+0x22/0x30 [337571.284251] ? commit_cowonly_roots+0x11f/0x250 [btrfs] [337571.284531] btrfs_commit_transaction+0x42e/0xf90 [btrfs] [337571.284803] ? _raw_spin_unlock+0x15/0x30 [337571.285031] ? release_extent_buffer+0x103/0x130 [btrfs] [337571.285305] reset_balance_state+0x152/0x1b0 [btrfs] [337571.285578] btrfs_balance+0xa50/0x11e0 [btrfs] [337571.285864] ? __kmem_cache_alloc_node+0x14a/0x410 [337571.286086] btrfs_ioctl+0x249a/0x3320 [btrfs] [337571.286358] ? mod_objcg_state+0xd2/0x360 [337571.286577] ? refill_obj_stock+0xb0/0x160 [337571.286798] ? seq_release+0x25/0x30 [337571.287016] ? __rseq_handle_notify_resume+0x3ba/0x4b0 [337571.287235] ? percpu_counter_add_batch+0x2e/0xa0 [337571.287455] ? __x64_sys_ioctl+0x88/0xc0 [337571.287675] __x64_sys_ioctl+0x88/0xc0 [337571.287901] do_syscall_64+0x38/0x90 [337571.288126] entry_SYSCALL_64_after_hwframe+0x72/0xdc [337571.288352] RIP: 0033:0x7f478aaffe9b So fix this by locking struct btrfs_fs_info::trans_lock before deleting the free space root from that list. Fixes: a5ed91828518 ("Btrfs: implement the free space B-tree") Signed-off-by: Filipe Manana --- fs/btrfs/free-space-tree.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/btrfs/free-space-tree.c b/fs/btrfs/free-space-tree.c index b21da1446f2a..045ddce32eca 100644 --- a/fs/btrfs/free-space-tree.c +++ b/fs/btrfs/free-space-tree.c @@ -1280,7 +1280,10 @@ int btrfs_delete_free_space_tree(struct btrfs_fs_info *fs_info) goto abort; btrfs_global_root_delete(free_space_root); + + spin_lock(&fs_info->trans_lock); list_del(&free_space_root->dirty_list); + spin_unlock(&fs_info->trans_lock); btrfs_tree_lock(free_space_root->node); btrfs_clear_buffer_dirty(trans, free_space_root->node); From patchwork Mon Jun 19 16:21:49 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Filipe Manana X-Patchwork-Id: 13284807 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4DBFEB64DC for ; Mon, 19 Jun 2023 16:22:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231967AbjFSQWD (ORCPT ); Mon, 19 Jun 2023 12:22:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37772 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231403AbjFSQWB (ORCPT ); Mon, 19 Jun 2023 12:22:01 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 14B48E60 for ; Mon, 19 Jun 2023 09:22:01 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9E8EB60CEC for ; Mon, 19 Jun 2023 16:22:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82356C433C9 for ; Mon, 19 Jun 2023 16:21:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1687191720; bh=pojtDB3XZu2yHxdORW20bVueq03oxwBlLxjihHRH0DE=; h=From:To:Subject:Date:In-Reply-To:References:From; b=kPdl8HF1wA2ljZIerZIGs39M5jFTjQs5nyMcN4+DJL3sDJXV9yfO7xKxg4VD2dOvG y5KGcA7qF8Qh/PT3nQUN/ClrPauDUqMf2a8TPU0eUnj3pY3/jbg7IDjrTSzvIJOkrG G9U56lhFqsDj/S0gc82VZ2ZhV4CYaw83bckqYO1JbCp1MlRIZ+cyvPUWm1c6vRzU04 n/nzWPsyseAzX6fxhEUueT8dYWD/tXv1npan9VA/hrAArxBH0HbPE/axpTXQWVWT5A Ix5XH1jg/V79OlyAPv89ppeSNWjW1pO3GEn4lrSB8EbqNtJ/yvbeG+KhzeoJoJ3Bud vioKbTEYtZY7A== From: fdmanana@kernel.org To: linux-btrfs@vger.kernel.org Subject: [PATCH 3/4] btrfs: add comment to struct btrfs_fs_info::dirty_cowonly_roots Date: Mon, 19 Jun 2023 17:21:49 +0100 Message-Id: <21a8b6c652a627a554c3f87f0df66e1ba808bc92.1687185583.git.fdmanana@suse.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Filipe Manana Add a comment to struct btrfs_fs_info::dirty_cowonly_roots to mention that struct btrfs_fs_info::trans_lock is the lock that protects that list. Signed-off-by: Filipe Manana --- fs/btrfs/fs.h | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h index 396e2a463480..203d2a267828 100644 --- a/fs/btrfs/fs.h +++ b/fs/btrfs/fs.h @@ -576,6 +576,7 @@ struct btrfs_fs_info { s32 dirty_metadata_batch; s32 delalloc_batch; + /* Protected by 'trans_lock'. */ struct list_head dirty_cowonly_roots; struct btrfs_fs_devices *fs_devices; From patchwork Mon Jun 19 16:21:50 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Filipe Manana X-Patchwork-Id: 13284808 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B4176EB64D9 for ; Mon, 19 Jun 2023 16:22:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232101AbjFSQWE (ORCPT ); Mon, 19 Jun 2023 12:22:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231966AbjFSQWC (ORCPT ); Mon, 19 Jun 2023 12:22:02 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B7D2BE63 for ; Mon, 19 Jun 2023 09:22:01 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9385560C97 for ; Mon, 19 Jun 2023 16:22:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7E5EEC433C0 for ; Mon, 19 Jun 2023 16:22:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1687191721; bh=HV6ATR1HJRlCBoaRnUwqqRzQ+ZDN1FI0VjENn5AQKD0=; h=From:To:Subject:Date:In-Reply-To:References:From; b=aL1hf8aHjbvl2zJmeUhjGQ0IwxeWQtmqZoYZaYv9DqnZ1O47/LurhrylpAn+Qzkhf bRDlhTGw4oappdD0ZAXzNcBTKYmkqt5CxNAvrqtdl0uNWYI1dWj7wGk0/AZW9Yp8Fj 6pfPFCnhc1mK2PYwV1SmQgEzL/zfHNdjAHtV0QqyoU98nWYLOGdWXcRvS4I09vHYdt Fjghs21Fp5xSJjGaHJMR4jyhiV0u/cddClFfFHAwr/EyXNroogzNiBuDTfCHQihS4q a0beHCOKLbY3WlNDbfNar2mFiV6hqRrZT9Ti3hy+69o5B/ltJ9U2rUZhiiRVfOwR5b U+dejruAUBFHw== From: fdmanana@kernel.org To: linux-btrfs@vger.kernel.org Subject: [PATCH 4/4] btrfs: fix race between quota disable and relocation Date: Mon, 19 Jun 2023 17:21:50 +0100 Message-Id: X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Filipe Manana If we disable quotas while we have a relocation of a metadata block group that has extents belonging to the quota root, we can cause the relocation to fail with -ENOENT. This is because relocation builds backref nodes for extents of the quota root and later needs to walk the backrefs and access the quota root - however if in between a task disables quotas, it results in deleting the quota root from the root tree (with btrfs_del_root(), called from btrfs_quota_disable(). This can be sporadically triggered by test case btrfs/255 from fstests: $ ./check btrfs/255 FSTYP -- btrfs PLATFORM -- Linux/x86_64 debian0 6.4.0-rc6-btrfs-next-134+ #1 SMP PREEMPT_DYNAMIC Thu Jun 15 11:59:28 WEST 2023 MKFS_OPTIONS -- /dev/sdc MOUNT_OPTIONS -- /dev/sdc /home/fdmanana/btrfs-tests/scratch_1 btrfs/255 6s ... _check_dmesg: something found in dmesg (see /home/fdmanana/git/hub/xfstests/results//btrfs/255.dmesg) - output mismatch (see /home/fdmanana/git/hub/xfstests/results//btrfs/255.out.bad) --- tests/btrfs/255.out 2023-03-02 21:47:53.876609426 +0000 +++ /home/fdmanana/git/hub/xfstests/results//btrfs/255.out.bad 2023-06-16 10:20:39.267563212 +0100 @@ -1,2 +1,4 @@ QA output created by 255 +ERROR: error during balancing '/home/fdmanana/btrfs-tests/scratch_1': No such file or directory +There may be more info in syslog - try dmesg | tail Silence is golden ... (Run 'diff -u /home/fdmanana/git/hub/xfstests/tests/btrfs/255.out /home/fdmanana/git/hub/xfstests/results//btrfs/255.out.bad' to see the entire diff) Ran: btrfs/255 Failures: btrfs/255 Failed 1 of 1 tests To fix this make the quota disable operation take the cleaner mutex, as relocation of a block group also takes this mutex. This is also what we do when deleting a subvolume/snapshot, we take the cleaner mutex in the cleaner kthread (at cleaner_kthread()) and then we call btrfs_del_root() at btrfs_drop_snapshot() while under the protection of the cleaner mutex. Fixes: bed92eae26cc ("Btrfs: qgroup implementation and prototypes") Signed-off-by: Filipe Manana --- fs/btrfs/qgroup.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index f8735b31da16..da1f84a0eb29 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1232,12 +1232,23 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info) int ret = 0; /* - * We need to have subvol_sem write locked, to prevent races between - * concurrent tasks trying to disable quotas, because we will unlock - * and relock qgroup_ioctl_lock across BTRFS_FS_QUOTA_ENABLED changes. + * We need to have subvol_sem write locked to prevent races with + * snapshot creation. */ lockdep_assert_held_write(&fs_info->subvol_sem); + /* + * Lock the cleaner mutex to prevent races with concurrent relocation, + * because relocation may be building backrefs for blocks of the quota + * root while we are deleting the root. This is like dropping fs roots + * of deleted snapshots/subvolumes, we need the same protection. + * + * This also prevents races between concurrent tasks trying to disable + * quotas, because we will unlock and relock qgroup_ioctl_lock across + * BTRFS_FS_QUOTA_ENABLED changes. + */ + mutex_lock(&fs_info->cleaner_mutex); + mutex_lock(&fs_info->qgroup_ioctl_lock); if (!fs_info->quota_root) goto out; @@ -1319,6 +1330,7 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info) btrfs_end_transaction(trans); else if (trans) ret = btrfs_end_transaction(trans); + mutex_unlock(&fs_info->cleaner_mutex); return ret; }