From 2a85d9cac160bb5b845985a60007cc8348d77def Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Mon, 10 Feb 2014 17:07:16 +0800 Subject: [PATCH] Btrfs: fix possible deadlock in btrfs_cleanup_transaction [13654.480669] ====================================================== [13654.480905] [ INFO: possible circular locking dependency detected ] [13654.481003] 3.12.0+ #4 Tainted: G W O [13654.481060] ------------------------------------------------------- [13654.481060] btrfs-transacti/9347 is trying to acquire lock: [13654.481060] (&(&root->ordered_extent_lock)->rlock){+.+...}, at: [] btrfs_cleanup_transaction+0x271/0x570 [btrfs] [13654.481060] but task is already holding lock: [13654.481060] (&(&fs_info->ordered_root_lock)->rlock){+.+...}, at: [] btrfs_cleanup_transaction+0x1e5/0x570 [btrfs] [13654.481060] which lock already depends on the new lock. [13654.481060] the existing dependency chain (in reverse order) is: [13654.481060] -> #1 (&(&fs_info->ordered_root_lock)->rlock){+.+...}: [13654.481060] [] lock_acquire+0x93/0x130 [13654.481060] [] _raw_spin_lock+0x41/0x50 [13654.481060] [] __btrfs_add_ordered_extent+0x39b/0x450 [btrfs] [13654.481060] [] btrfs_add_ordered_extent+0x32/0x40 [btrfs] [13654.481060] [] run_delalloc_nocow+0x78a/0x9d0 [btrfs] [13654.481060] [] run_delalloc_range+0x31d/0x390 [btrfs] [13654.481060] [] __extent_writepage+0x310/0x780 [btrfs] [13654.481060] [] extent_write_cache_pages.isra.29.constprop.48+0x29a/0x410 [btrfs] [13654.481060] [] extent_writepages+0x4d/0x70 [btrfs] [13654.481060] [] btrfs_writepages+0x28/0x30 [btrfs] [13654.481060] [] do_writepages+0x21/0x50 [13654.481060] [] __filemap_fdatawrite_range+0x59/0x60 [13654.481060] [] filemap_fdatawrite_range+0x13/0x20 [13654.481060] [] btrfs_wait_ordered_range+0x49/0x140 [btrfs] [13654.481060] [] __btrfs_write_out_cache+0x682/0x8b0 [btrfs] [13654.481060] [] btrfs_write_out_cache+0x8d/0xe0 [btrfs] [13654.481060] [] btrfs_write_dirty_block_groups+0x593/0x680 [btrfs] [13654.481060] [] commit_cowonly_roots+0x14b/0x20d [btrfs] [13654.481060] [] btrfs_commit_transaction+0x43a/0x9d0 [btrfs] [13654.481060] [] btrfs_create_uuid_tree+0x5a/0x100 [btrfs] [13654.481060] [] open_ctree+0x21da/0x2210 [btrfs] [13654.481060] [] btrfs_mount+0x68e/0x870 [btrfs] [13654.481060] [] mount_fs+0x39/0x1b0 [13654.481060] [] vfs_kern_mount+0x63/0xf0 [13654.481060] [] do_mount+0x23e/0xa90 [13654.481060] [] SyS_mount+0x83/0xc0 [13654.481060] [] system_call_fastpath+0x16/0x1b [13654.481060] -> #0 (&(&root->ordered_extent_lock)->rlock){+.+...}: [13654.481060] [] __lock_acquire+0x150a/0x1a70 [13654.481060] [] lock_acquire+0x93/0x130 [13654.481060] [] _raw_spin_lock+0x41/0x50 [13654.481060] [] btrfs_cleanup_transaction+0x271/0x570 [btrfs] [13654.481060] [] transaction_kthread+0x22e/0x270 [btrfs] [13654.481060] [] kthread+0xea/0xf0 [13654.481060] [] ret_from_fork+0x7c/0xb0 [13654.481060] other info that might help us debug this: [13654.481060] Possible unsafe locking scenario: [13654.481060] CPU0 CPU1 [13654.481060] ---- ---- [13654.481060] lock(&(&fs_info->ordered_root_lock)->rlock); [13654.481060] lock(&(&root->ordered_extent_lock)->rlock); [13654.481060] lock(&(&fs_info->ordered_root_lock)->rlock); [13654.481060] lock(&(&root->ordered_extent_lock)->rlock); [13654.481060] *** DEADLOCK *** [...] ====================================================== btrfs_destroy_all_ordered_extents() gets &fs_info->ordered_root_lock __BEFORE__ acquiring &root->ordered_extent_lock, while btrfs_[add,remove]_ordered_extent() acquires &fs_info->ordered_root_lock __AFTER__ getting &root->ordered_extent_lock. This patch fixes the above problem. Signed-off-by: Liu Bo Signed-off-by: Josef Bacik --- fs/btrfs/disk-io.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 74c9be89fc0c..cc1b4237dc62 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -3808,9 +3808,11 @@ static void btrfs_destroy_all_ordered_extents(struct btrfs_fs_info *fs_info) list_move_tail(&root->ordered_root, &fs_info->ordered_roots); + spin_unlock(&fs_info->ordered_root_lock); btrfs_destroy_ordered_extents(root); - cond_resched_lock(&fs_info->ordered_root_lock); + cond_resched(); + spin_lock(&fs_info->ordered_root_lock); } spin_unlock(&fs_info->ordered_root_lock); } -- 2.20.1