From: Larry Chen Date: Mon, 27 Aug 2018 16:01:21 +0800 Subject: [Ocfs2-devel] [PATCH] fix dead lock caused by ocfs2_defrag_extent Message-ID: <20180827080121.31145-1-lchen@suse.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: mfasheh@suse.com, jlbec@evilplan.org Cc: linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com, akpm@linux-foundation.org ocfs2_defrag_extent may fall into dead lock. ocfs2_ioctl_move_extents ocfs2_ioctl_move_extents ocfs2_move_extents ocfs2_defrag_extent ocfs2_lock_allocators_move_extents ocfs2_reserve_clusters inode_lock GLOBAL_BITMAP_SYSTEM_INODE __ocfs2_flush_truncate_log inode_lock GLOBAL_BITMAP_SYSTEM_INODE As back trace shows above, ocfs2_reserve_clusters will call inode_lock against the global bitmap if local allocator has not sufficient cluters. Once global bitmap could meet the demand, ocfs2_reserve_cluster will return success with global bitmap locked. After ocfs2_reserve_cluster, if truncate log is full, __ocfs2_flush_truncate_log will definitely fall into dead lock because it needs to inode_lock global bitmap, which has already been locked. To fix this bug, we could remove from ocfs2_lock_allocators_move_extents the code which intends to lock global allocator, and put the removed code after __ocfs2_flush_truncate_log The ocfs2_lock_allocators_move_extents has been refered by 2 places, one is here, the other does not need the data allocator context, which means this patch does not affect the caller so far. Signed-off-by: Larry Chen --- fs/ocfs2/move_extents.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/fs/ocfs2/move_extents.c b/fs/ocfs2/move_extents.c index 7eb3b0a6347e..064dedf40d74 100644 --- a/fs/ocfs2/move_extents.c +++ b/fs/ocfs2/move_extents.c @@ -192,13 +192,6 @@ static int ocfs2_lock_allocators_move_extents(struct inode *inode, goto out; } - if (data_ac) { - ret = ocfs2_reserve_clusters(osb, clusters_to_move, data_ac); - if (ret) { - mlog_errno(ret); - goto out; - } - } *credits += ocfs2_calc_extend_credits(osb->sb, et->et_root_el); @@ -283,6 +276,12 @@ static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context, } } + ret = ocfs2_reserve_clusters(osb, *len, &context->data_ac); + if (ret) { + mlog_errno(ret); + goto out_unlock_mutex; + } + handle = ocfs2_start_trans(osb, credits); if (IS_ERR(handle)) { ret = PTR_ERR(handle); -- 2.13.7