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=-9.8 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=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 43540C433E3 for ; Thu, 20 Aug 2020 12:28:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 208BF20738 for ; Thu, 20 Aug 2020 12:28:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597926489; bh=2hTiHBj5GDxe6smlNZQ1HWaL2bz/g+aouyUMLlufD04=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Qpap9km5k7anwOWONCpK+87yMSDBR9/SWskPLV/iHSmDfre77g/ZOBf0VMME+IdVn 5nWQmMkLddweFFDa/Lf0zuEqzaTOyxNhe4eIpRHWOQ653cmYgDqC9dUlhEptlhopGY 8wnv4W4zKsUBKKiruEFyFtWKMiNlcKzl6rIVRxzw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729225AbgHTM2C (ORCPT ); Thu, 20 Aug 2020 08:28:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:33042 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729865AbgHTJv5 (ORCPT ); Thu, 20 Aug 2020 05:51:57 -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 D7A9D2067C; Thu, 20 Aug 2020 09:51:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597917117; bh=2hTiHBj5GDxe6smlNZQ1HWaL2bz/g+aouyUMLlufD04=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BkTjfU75V2djz+o4wzDlL4xwahocRv9lQyPjukzVjzVwT702X/G7z9MLohuR3zLpl bJOSFpULhojEO4D00DMAy0cBXDNYMoueSW0JSiMt1lCEnVSlwslbX/JAriE9XHjh+3 TKMCwCJkQVNkY87/4378ENdEacctYopi3Z8IqLBY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Greed Rong , Josef Bacik , Qu Wenruo , David Sterba Subject: [PATCH 4.19 10/92] btrfs: dont allocate anonymous block device for user invisible roots Date: Thu, 20 Aug 2020 11:20:55 +0200 Message-Id: <20200820091538.048068141@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200820091537.490965042@linuxfoundation.org> References: <20200820091537.490965042@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Qu Wenruo commit 851fd730a743e072badaf67caf39883e32439431 upstream. [BUG] When a lot of subvolumes are created, there is a user report about transaction aborted: BTRFS: Transaction aborted (error -24) WARNING: CPU: 17 PID: 17041 at fs/btrfs/transaction.c:1576 create_pending_snapshot+0xbc4/0xd10 [btrfs] RIP: 0010:create_pending_snapshot+0xbc4/0xd10 [btrfs] Call Trace: create_pending_snapshots+0x82/0xa0 [btrfs] btrfs_commit_transaction+0x275/0x8c0 [btrfs] btrfs_mksubvol+0x4b9/0x500 [btrfs] btrfs_ioctl_snap_create_transid+0x174/0x180 [btrfs] btrfs_ioctl_snap_create_v2+0x11c/0x180 [btrfs] btrfs_ioctl+0x11a4/0x2da0 [btrfs] do_vfs_ioctl+0xa9/0x640 ksys_ioctl+0x67/0x90 __x64_sys_ioctl+0x1a/0x20 do_syscall_64+0x5a/0x110 entry_SYSCALL_64_after_hwframe+0x44/0xa9 ---[ end trace 33f2f83f3d5250e9 ]--- BTRFS: error (device sda1) in create_pending_snapshot:1576: errno=-24 unknown BTRFS info (device sda1): forced readonly BTRFS warning (device sda1): Skipping commit of aborted transaction. BTRFS: error (device sda1) in cleanup_transaction:1831: errno=-24 unknown [CAUSE] The error is EMFILE (Too many files open) and comes from the anonymous block device allocation. The ids are in a shared pool of size 1<<20. The ids are assigned to live subvolumes, ie. the root structure exists in memory (eg. after creation or after the root appears in some path). The pool could be exhausted if the numbers are not reclaimed fast enough, after subvolume deletion or if other system component uses the anon block devices. [WORKAROUND] Since it's not possible to completely solve the problem, we can only minimize the time the id is allocated to a subvolume root. Firstly, we can reduce the use of anon_dev by trees that are not subvolume roots, like data reloc tree. This patch will do extra check on root objectid, to skip roots that don't need anon_dev. Currently it's only data reloc tree and orphan roots. Reported-by: Greed Rong Link: https://lore.kernel.org/linux-btrfs/CA+UqX+NTrZ6boGnWHhSeZmEY5J76CTqmYjO2S+=tHJX7nb9DPw@mail.gmail.com/ CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/disk-io.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1500,9 +1500,16 @@ int btrfs_init_fs_root(struct btrfs_root spin_lock_init(&root->ino_cache_lock); init_waitqueue_head(&root->ino_cache_wait); - ret = get_anon_bdev(&root->anon_dev); - if (ret) - goto fail; + /* + * Don't assign anonymous block device to roots that are not exposed to + * userspace, the id pool is limited to 1M + */ + if (is_fstree(root->root_key.objectid) && + btrfs_root_refs(&root->root_item) > 0) { + ret = get_anon_bdev(&root->anon_dev); + if (ret) + goto fail; + } mutex_lock(&root->objectid_mutex); ret = btrfs_find_highest_objectid(root,