1 files changed, 12 insertions, 1 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 5989a92236f7..2854c824ab64 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4935,7 +4935,18 @@ int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
         em = lookup_extent_mapping(em_tree, chunk_start, 1);
         read_unlock(&em_tree->lock);
 
-        BUG_ON(!em || em->start != chunk_start);
+        if (!em) {
+                printk(KERN_ERR "btrfs: couldn't find em for chunk %Lu\n",
+                       chunk_start);
+                return -EIO;
+        }
+
+        if (em->start != chunk_start) {
+                printk(KERN_ERR "btrfs: bad chunk start, em=%Lu, wanted=%Lu\n",
+                       em->start, chunk_start);
+                free_extent_map(em);
+                return -EIO;
+        }
         map = (struct map_lookup *)em->bdev;
 
         length = em->len;