From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754806Ab3LRVOj (ORCPT ); Wed, 18 Dec 2013 16:14:39 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:36654 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754700Ab3LRVOW (ORCPT ); Wed, 18 Dec 2013 16:14:22 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Liu Bo , Josef Bacik , Chris Mason Subject: [PATCH 3.12 114/118] Btrfs: fix a crash when running balance and defrag concurrently Date: Wed, 18 Dec 2013 13:12:31 -0800 Message-Id: <20131218211222.685514349@linuxfoundation.org> X-Mailer: git-send-email 1.8.5.1.163.gd7aced9 In-Reply-To: <20131218211219.461663463@linuxfoundation.org> References: <20131218211219.461663463@linuxfoundation.org> User-Agent: quilt/0.61-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Liu Bo commit 48ec47364b6d493f0a9cdc116977bf3f34e5c3ec upstream. Running balance and defrag concurrently can end up with a crash: kernel BUG at fs/btrfs/relocation.c:4528! RIP: 0010:[] [] btrfs_reloc_cow_block+ 0x1eb/0x230 [btrfs] Call Trace: [] ? update_ref_for_cow+0x241/0x380 [btrfs] [] ? copy_extent_buffer+0xad/0x110 [btrfs] [] __btrfs_cow_block+0x3a1/0x520 [btrfs] [] btrfs_cow_block+0x116/0x1b0 [btrfs] [] btrfs_search_slot+0x43d/0x970 [btrfs] [] btrfs_lookup_file_extent+0x37/0x40 [btrfs] [] __btrfs_drop_extents+0x11e/0xae0 [btrfs] [] ? generic_bin_search.constprop.39+0x8d/0x1a0 [btrfs] [] ? kmem_cache_alloc+0x1da/0x200 [] ? btrfs_alloc_path+0x1a/0x20 [btrfs] [] btrfs_drop_extents+0x60/0x90 [btrfs] [] relink_extent_backref+0x2ed/0x780 [btrfs] [] ? btrfs_submit_bio_hook+0x1e0/0x1e0 [btrfs] [] ? iterate_inodes_from_logical+0x87/0xa0 [btrfs] [] btrfs_finish_ordered_io+0x229/0xac0 [btrfs] [] finish_ordered_fn+0x15/0x20 [btrfs] [] worker_loop+0x125/0x4e0 [btrfs] [] ? btrfs_queue_worker+0x300/0x300 [btrfs] [] kthread+0xc0/0xd0 [] ? insert_kthread_work+0x40/0x40 [] ret_from_fork+0x7c/0xb0 [] ? insert_kthread_work+0x40/0x40 ---------------------------------------------------------------------- It turns out to be that balance operation will bump root's @last_snapshot, which enables snapshot-aware defrag path, and backref walking stuff will find data reloc tree as refs' parent, and hit the BUG_ON() during COW. As data reloc tree's data is just for relocation purpose, and will be deleted right after relocation is done, it's unnecessary to walk those refs belonged to data reloc tree, it'd be better to skip them. Signed-off-by: Liu Bo Signed-off-by: Josef Bacik Signed-off-by: Chris Mason Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/backref.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -185,6 +185,9 @@ static int __add_prelim_ref(struct list_ { struct __prelim_ref *ref; + if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID) + return 0; + ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask); if (!ref) return -ENOMEM;