ocfs2: fix deadlock caused by ocfs2_defrag_extent()

[ Upstream commit e21e57445a64598b29a6f629688f9b9a39e7242a ]

ocfs2_defrag_extent may fall into deadlock.

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 backtrace 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 deadlock 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().

ocfs2_lock_allocators_move_extents() is referred 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.

Link: http://lkml.kernel.org/r/20181101071422.14470-1-lchen@suse.com
Signed-off-by: Larry Chen <lchen@suse.com>
Reviewed-by: Changwei Ge <ge.changwei@h3c.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ocfs2/move_extents.c b/fs/ocfs2/move_extents.c
index 7eb3b0a6347ef74990589ac47f5b4823441c8135..f55f82ca342502540757665236e73e92598709e1 100644 (file)
--- a/fs/ocfs2/move_extents.c
+++ b/fs/ocfs2/move_extents.c
@@ -156,18 +156,14 @@ out:
 }
 
 /*
- * lock allocators, and reserving appropriate number of bits for
- * meta blocks and data clusters.
- *
- * in some cases, we don't need to reserve clusters, just let data_ac
- * be NULL.
+ * lock allocator, and reserve appropriate number of bits for
+ * meta blocks.
  */
-static int ocfs2_lock_allocators_move_extents(struct inode *inode,
+static int ocfs2_lock_meta_allocator_move_extents(struct inode *inode,
                                        struct ocfs2_extent_tree *et,
                                        u32 clusters_to_move,
                                        u32 extents_to_split,
                                        struct ocfs2_alloc_context **meta_ac,
-                                       struct ocfs2_alloc_context **data_ac,
                                        int extra_blocks,
                                        int *credits)
 {
@@ -192,13 +188,6 @@ 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);
 
@@ -257,10 +246,10 @@ static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context,
                }
        }
 
-       ret = ocfs2_lock_allocators_move_extents(inode, &context->et, *len, 1,
-                                                &context->meta_ac,
-                                                &context->data_ac,
-                                                extra_blocks, &credits);
+       ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
+                                               *len, 1,
+                                               &context->meta_ac,
+                                               extra_blocks, &credits);
        if (ret) {
                mlog_errno(ret);
                goto out;
@@ -283,6 +272,21 @@ static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context,
                }
        }
 
+       /*
+        * Make sure ocfs2_reserve_cluster is called after
+        * __ocfs2_flush_truncate_log, otherwise, dead lock may happen.
+        *
+        * If ocfs2_reserve_cluster is called
+        * before __ocfs2_flush_truncate_log, dead lock on global bitmap
+        * may happen.
+        *
+        */
+       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);
@@ -600,9 +604,10 @@ static int ocfs2_move_extent(struct ocfs2_move_extents_context *context,
                }
        }
 
-       ret = ocfs2_lock_allocators_move_extents(inode, &context->et, len, 1,
-                                                &context->meta_ac,
-                                                NULL, extra_blocks, &credits);
+       ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
+                                               len, 1,
+                                               &context->meta_ac,
+                                               extra_blocks, &credits);
        if (ret) {
                mlog_errno(ret);
                goto out;