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=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 1B177C433E5 for ; Tue, 14 Jul 2020 19:01:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ECB5E22B4E for ; Tue, 14 Jul 2020 19:01:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594753318; bh=/SwL4lhyb9H479yrYfVEdAQXaqBeWOFBvjRzYCTP14M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=QW3subQm6HDszw/GFz25a8an0xbRgXWiX5UoHZBray0f2DaJy/VoEQXUJlw0GH0V1 Fi40gdRR+4DgM5a6nF38YhezyqV08a52IXYt7Vzggt2FU5BIixQIcCpnWlM4Fskve7 8z4t3YKhtgdnOcvGH+n3kAUMpS+HPAwBglzXB4ZY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730780AbgGNS7I (ORCPT ); Tue, 14 Jul 2020 14:59:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:57586 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731067AbgGNS7C (ORCPT ); Tue, 14 Jul 2020 14:59:02 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 93ACE229CA; Tue, 14 Jul 2020 18:59:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594753142; bh=/SwL4lhyb9H479yrYfVEdAQXaqBeWOFBvjRzYCTP14M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NYPk0qNhqoNvX2WHbor0HWuhyARbH8n5oGNT8GcV1RL661+k+GKTyEMzApIN44oXA pDm3GbozZbUZJpymm65mSXTvJi+jltUu2myfQ2r1OniGuWOkATcseGbKD0zpYC9roO 63TZRCl+Jjf0xvVnbcqR5tpciPkd+Q9lBfsb1zpY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Marcos Paulo de Souza , Anand Jain , Qu Wenruo , David Sterba Subject: [PATCH 5.7 136/166] btrfs: discard: add missing put when grabbing block group from unused list Date: Tue, 14 Jul 2020 20:45:01 +0200 Message-Id: <20200714184122.344961940@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200714184115.844176932@linuxfoundation.org> References: <20200714184115.844176932@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Qu Wenruo commit 04e484c5973ed0f9234c97685c3c5e1ebf0d6eb6 upstream. [BUG] The following small test script can trigger ASSERT() at unmount time: mkfs.btrfs -f $dev mount $dev $mnt mount -o remount,discard=async $mnt umount $mnt The call trace: assertion failed: atomic_read(&block_group->count) == 1, in fs/btrfs/block-group.c:3431 ------------[ cut here ]------------ kernel BUG at fs/btrfs/ctree.h:3204! invalid opcode: 0000 [#1] PREEMPT SMP NOPTI CPU: 4 PID: 10389 Comm: umount Tainted: G O 5.8.0-rc3-custom+ #68 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: btrfs_free_block_groups.cold+0x22/0x55 [btrfs] close_ctree+0x2cb/0x323 [btrfs] btrfs_put_super+0x15/0x17 [btrfs] generic_shutdown_super+0x72/0x110 kill_anon_super+0x18/0x30 btrfs_kill_super+0x17/0x30 [btrfs] deactivate_locked_super+0x3b/0xa0 deactivate_super+0x40/0x50 cleanup_mnt+0x135/0x190 __cleanup_mnt+0x12/0x20 task_work_run+0x64/0xb0 __prepare_exit_to_usermode+0x1bc/0x1c0 __syscall_return_slowpath+0x47/0x230 do_syscall_64+0x64/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 The code: ASSERT(atomic_read(&block_group->count) == 1); btrfs_put_block_group(block_group); [CAUSE] Obviously it's some btrfs_get_block_group() call doesn't get its put call. The offending btrfs_get_block_group() happens here: void btrfs_mark_bg_unused(struct btrfs_block_group *bg) { if (list_empty(&bg->bg_list)) { btrfs_get_block_group(bg); list_add_tail(&bg->bg_list, &fs_info->unused_bgs); } } So every call sites removing the block group from unused_bgs list should reduce the ref count of that block group. However for async discard, it didn't follow the call convention: void btrfs_discard_punt_unused_bgs_list(struct btrfs_fs_info *fs_info) { list_for_each_entry_safe(block_group, next, &fs_info->unused_bgs, bg_list) { list_del_init(&block_group->bg_list); btrfs_discard_queue_work(&fs_info->discard_ctl, block_group); } } And in btrfs_discard_queue_work(), it doesn't call btrfs_put_block_group() either. [FIX] Fix the problem by reducing the reference count when we grab the block group from unused_bgs list. Reported-by: Marcos Paulo de Souza Fixes: 6e80d4f8c422 ("btrfs: handle empty block_group removal for async discard") CC: stable@vger.kernel.org # 5.6+ Tested-by: Marcos Paulo de Souza Reviewed-by: Anand Jain Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/discard.c | 1 + 1 file changed, 1 insertion(+) --- a/fs/btrfs/discard.c +++ b/fs/btrfs/discard.c @@ -619,6 +619,7 @@ void btrfs_discard_punt_unused_bgs_list( list_for_each_entry_safe(block_group, next, &fs_info->unused_bgs, bg_list) { list_del_init(&block_group->bg_list); + btrfs_put_block_group(block_group); btrfs_discard_queue_work(&fs_info->discard_ctl, block_group); } spin_unlock(&fs_info->unused_bgs_lock);