1 files changed, 17 insertions, 4 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index dc84daee6bc4..72a2b9c28e9f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -265,10 +265,6 @@ static int caching_kthread(void *data)
 
         atomic_inc(&block_group->space_info->caching_threads);
         last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);
-again:
-        /* need to make sure the commit_root doesn't disappear */
-        down_read(&fs_info->extent_commit_sem);
-
         /*
          * We don't want to deadlock with somebody trying to allocate a new
          * extent for the extent root while also trying to search the extent
@@ -282,6 +278,10 @@ again:
         key.objectid = last;
         key.offset = 0;
         btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
+again:
+        /* need to make sure the commit_root doesn't disappear */
+        down_read(&fs_info->extent_commit_sem);
+
         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
         if (ret < 0)
                 goto err;
@@ -304,6 +304,19 @@ again:
 
                         if (need_resched() ||
                             btrfs_transaction_in_commit(fs_info)) {
+                                leaf = path->nodes[0];
+
+                                /* this shouldn't happen, but if the
+                                 * leaf is empty just move on.
+                                 */
+                                if (btrfs_header_nritems(leaf) == 0)
+                                        break;
+                                /*
+                                 * we need to copy the key out so that
+                                 * we are sure the next search advances
+                                 * us forward in the btree.
+                                 */
+                                btrfs_item_key_to_cpu(leaf, &key, 0);
                                 btrfs_release_path(fs_info->extent_root, path);
                                 up_read(&fs_info->extent_commit_sem);
                                 schedule_timeout(1);