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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 CA27EC4742C for ; Fri, 30 Oct 2020 21:03:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 72D212076D for ; Fri, 30 Oct 2020 21:03:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=toxicpanda-com.20150623.gappssmtp.com header.i=@toxicpanda-com.20150623.gappssmtp.com header.b="HhUAIN+v" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727748AbgJ3VDi (ORCPT ); Fri, 30 Oct 2020 17:03:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726917AbgJ3VDi (ORCPT ); Fri, 30 Oct 2020 17:03:38 -0400 Received: from mail-qt1-x844.google.com (mail-qt1-x844.google.com [IPv6:2607:f8b0:4864:20::844]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7502AC0613CF for ; Fri, 30 Oct 2020 14:03:36 -0700 (PDT) Received: by mail-qt1-x844.google.com with SMTP id s39so5171080qtb.2 for ; Fri, 30 Oct 2020 14:03:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toxicpanda-com.20150623.gappssmtp.com; s=20150623; h=from:to:subject:date:message-id:in-reply-to:references:mime-version :content-transfer-encoding; bh=s7FiwgcGjSfDhX/Lpxflgb2UTT8b3aN4mUKTmLw4FpI=; b=HhUAIN+v5dzKMzIILYF6xWB6w6bPeScf2FvidW8ZE4rAFbmaAbI6bDU9xMBSySmMHW oY1VSg9aoIY4d+bMV5Pk1OKWvRSYGyT9nbW9CT/VY6W1J2Jo2xTlkbSwR4r7ig2JrY5M C7lzZfrwgt6Zb4x/9R0If8PyrDxtA+Sfcn/A2Ld8EJZ70V2M9a32ZEJVcRQyfxb+QeQT C/Te3wA+ZnpAF23yKDeWxeadYAhkMb15rR1/6R/SVhNVF2uAeAx2sdqc+a4fBeVSLpCu Hhjc1JwDPb+9oFA6VLdHlvzZw/Udjuo6XrNUx2rlzFpY/M9zM/kIwi6E+BEMhkjjyL75 kahA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=s7FiwgcGjSfDhX/Lpxflgb2UTT8b3aN4mUKTmLw4FpI=; b=FM7fHHrs6r7rX+Trxnj8kPs0s0P4Krx2Vq62RWrgAj4tz7+SqueexGSJoYZXfJguFY Uq7jTsB7q7nsdKG1gXEELVjSnlRU8YePRT0Y63CYZ0LyH1lqVpsFfwnh//Mu2cs3s6w7 Eh7vgj609iX1IXcJ01UDiTsFt1Vd9Ov+m0Y6MEDsNZd3HleUewuvBWUdMt8TShHhJLjT 2d2bzaE71o+SsSz+qn1+iE4kqv3/9aLXFsddVIgSpHtlQUgFzRQwZs4adHGx2iYMjVMH I4oMz/+CFTfV/izlDCtutlE/z5v88gIjmNbaAPsA5L+mMkgAcP7A8JYZ4g1yB7vHtogg iiqQ== X-Gm-Message-State: AOAM530leeZRG68mxw/ZaNEUq75j1qQBw0zSlNlcS9MWiZIKbDJ57rLw 4RYKXAWQlTSQyF+Oap/EAzstwKKv5N/C5N31 X-Google-Smtp-Source: ABdhPJzNelHSXcB80f7t7v0c3qMoqACh7Pq/HKXFfgFYuykCNtj/MOxNrXcNjDdigZJszU1ltTBGuw== X-Received: by 2002:ac8:5916:: with SMTP id 22mr4061842qty.352.1604091815220; Fri, 30 Oct 2020 14:03:35 -0700 (PDT) Received: from localhost (cpe-174-109-172-136.nc.res.rr.com. [174.109.172.136]) by smtp.gmail.com with ESMTPSA id z26sm3290419qki.40.2020.10.30.14.03.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Oct 2020 14:03:34 -0700 (PDT) From: Josef Bacik To: linux-btrfs@vger.kernel.org, kernel-team@fb.com Subject: [PATCH 14/14] btrfs: set the lockdep class for ebs on creation Date: Fri, 30 Oct 2020 17:03:06 -0400 Message-Id: <684352674d9bc1db4373af4b94cbe56667f90503.1604091530.git.josef@toxicpanda.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Both Filipe and Fedora QA recently hit the following lockdep splat WARNING: possible recursive locking detected 5.10.0-0.rc1.20201028gited8780e3f2ec.57.fc34.x86_64 #1 Not tainted -------------------------------------------- rsync/2610 is trying to acquire lock: ffff89617ed48f20 (&eb->lock){++++}-{2:2}, at: btrfs_tree_read_lock_atomic+0x34/0x140 but task is already holding lock: ffff8961757b1130 (&eb->lock){++++}-{2:2}, at: btrfs_tree_read_lock_atomic+0x34/0x140 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&eb->lock); lock(&eb->lock); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by rsync/2610: #0: ffff896107212b90 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: walk_component+0x10c/0x190 #1: ffff8961757b1130 (&eb->lock){++++}-{2:2}, at: btrfs_tree_read_lock_atomic+0x34/0x140 stack backtrace: CPU: 1 PID: 2610 Comm: rsync Not tainted 5.10.0-0.rc1.20201028gited8780e3f2ec.57.fc34.x86_64 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 Call Trace: dump_stack+0x8b/0xb0 __lock_acquire.cold+0x12d/0x2a4 ? kvm_sched_clock_read+0x14/0x30 ? sched_clock+0x5/0x10 lock_acquire+0xc8/0x400 ? btrfs_tree_read_lock_atomic+0x34/0x140 ? read_block_for_search.isra.0+0xdd/0x320 _raw_read_lock+0x3d/0xa0 ? btrfs_tree_read_lock_atomic+0x34/0x140 btrfs_tree_read_lock_atomic+0x34/0x140 btrfs_search_slot+0x616/0x9a0 btrfs_lookup_dir_item+0x6c/0xb0 btrfs_lookup_dentry+0xa8/0x520 ? lockdep_init_map_waits+0x4c/0x210 btrfs_lookup+0xe/0x30 __lookup_slow+0x10f/0x1e0 walk_component+0x11b/0x190 path_lookupat+0x72/0x1c0 filename_lookup+0x97/0x180 ? strncpy_from_user+0x96/0x1e0 ? getname_flags.part.0+0x45/0x1a0 vfs_statx+0x64/0x100 ? lockdep_hardirqs_on_prepare+0xff/0x180 ? _raw_spin_unlock_irqrestore+0x41/0x50 __do_sys_newlstat+0x26/0x40 ? lockdep_hardirqs_on_prepare+0xff/0x180 ? syscall_enter_from_user_mode+0x27/0x80 ? syscall_enter_from_user_mode+0x27/0x80 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 I have also seen a report of lockdep complaining about the lock class that was looked up being the same as the lock class on the lock we were using, but I can't find the report. These are problems that occur because we do not have the lockdep class set on the extent buffer until _after_ we read the eb in properly. This is problematic for concurrent readers, because we will create the extent buffer, lock it, and then attempt to read the extent buffer. If a second thread comes in and tries to do a search down the same path they'll get the above lockdep splat because the class isn't set properly on the extent buffer. There was a good reason for this, we generally didn't know the real owner of the eb until we read it, specifically in refcount'ed roots. However now all refcount'ed roots have the same class name, so we no longer need to worry about this. For non-refcount'ed tree's we know which root we're on based on the parent. Fix this by setting the lockdep class on the eb at creation time instead of read time. This will fix the splat and the weirdness where the class changes in the middle of locking the block. Signed-off-by: Josef Bacik --- fs/btrfs/disk-io.c | 3 --- fs/btrfs/extent-tree.c | 8 +++++--- fs/btrfs/extent_io.c | 1 + fs/btrfs/volumes.c | 1 - 4 files changed, 6 insertions(+), 7 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 989412501a92..d8ce8bbb3a45 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -578,9 +578,6 @@ int btrfs_validate_metadata_buffer(struct btrfs_io_bio *io_bio, u64 phy_offset, goto err; } - btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb), - eb, found_level); - csum_tree_block(eb, result); if (memcmp_extent_buffer(eb, result, 0, csum_size)) { diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index a2c611a83057..1ddd8f4e9564 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -4679,6 +4679,11 @@ btrfs_init_new_buffer(struct btrfs_trans_handle *trans, struct btrfs_root *root, return ERR_PTR(-EUCLEAN); } + /* + * This needs to stay, because we could allocate a free'd block from an + * old tree into a new tree, so we need to make sure this new block is + * set to the appropriate level and owner. + */ btrfs_set_buffer_lockdep_class(owner, buf, level); __btrfs_tree_lock(buf, nest); btrfs_clean_tree_block(buf); @@ -5069,9 +5074,6 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans, level - 1); if (IS_ERR(next)) return PTR_ERR(next); - - btrfs_set_buffer_lockdep_class(root->root_key.objectid, next, - level - 1); reada = 1; } btrfs_tree_lock(next); diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 0af8333ccca1..4e758d670fc1 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -5188,6 +5188,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info, eb = __alloc_extent_buffer(fs_info, start, len); if (!eb) return ERR_PTR(-ENOMEM); + btrfs_set_buffer_lockdep_class(owner_root, eb, level); num_pages = num_extent_pages(eb); for (i = 0; i < num_pages; i++, index++) { diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 9ef1a51379e9..ad244b44a3a1 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -6914,7 +6914,6 @@ int btrfs_read_sys_array(struct btrfs_fs_info *fs_info) if (IS_ERR(sb)) return PTR_ERR(sb); set_extent_buffer_uptodate(sb); - btrfs_set_buffer_lockdep_class(root->root_key.objectid, sb, 0); /* * The sb extent buffer is artificial and just used to read the system array. * set_extent_buffer_uptodate() call does not properly mark all it's -- 2.26.2