btrfs: don't BUG_ON() when 0 reference count at btrfs_lookup_extent_info()

Instead of doing a BUG_ON() handle the error by returning -EUCLEAN,
aborting the transaction and logging an error message.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 94dffe6b62520086149b3e9d7638a7e3d6f3d9be..23a7cac108eb88a21df18035b21bd4433920316c 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -164,9 +164,16 @@ search_again:
 
                ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
                num_refs = btrfs_extent_refs(leaf, ei);
+               if (unlikely(num_refs == 0)) {
+                       ret = -EUCLEAN;
+                       btrfs_err(fs_info,
+               "unexpected zero reference count for extent item (%llu %u %llu)",
+                                 key.objectid, key.type, key.offset);
+                       btrfs_abort_transaction(trans, ret);
+                       goto out_free;
+               }
                extent_flags = btrfs_extent_flags(leaf, ei);
                owner = btrfs_get_extent_owner_root(fs_info, leaf, path->slots[0]);
-               BUG_ON(num_refs == 0);
        } else {
                num_refs = 0;
                extent_flags = 0;
@@ -193,10 +200,19 @@ search_again:
                        goto search_again;
                }
                spin_lock(&head->lock);
-               if (head->extent_op && head->extent_op->update_flags)
+               if (head->extent_op && head->extent_op->update_flags) {
                        extent_flags |= head->extent_op->flags_to_set;
-               else
-                       BUG_ON(num_refs == 0);
+               } else if (unlikely(num_refs == 0)) {
+                       spin_unlock(&head->lock);
+                       mutex_unlock(&head->mutex);
+                       spin_unlock(&delayed_refs->lock);
+                       ret = -EUCLEAN;
+                       btrfs_err(fs_info,
+                         "unexpected zero reference count for extent %llu (%s)",
+                                 bytenr, metadata ? "metadata" : "data");
+                       btrfs_abort_transaction(trans, ret);
+                       goto out_free;
+               }
 
                num_refs += head->ref_mod;
                spin_unlock(&head->lock);