Btrfs: check inconsistence between chunk and block group

With btrfs-corrupt-block, one can drop one chunk item and mounting
will end up with a panic in btrfs_full_stripe_len().

This doesn't not remove the BUG_ON, but instead checks it a bit
earlier when we find the block group item.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 9fcb8c97083b..cab2f9c8d321 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -9887,7 +9887,22 @@ static int find_first_block_group(struct btrfs_root *root,
 
                 if (found_key.objectid >= key->objectid &&
                     found_key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
-                        ret = 0;
+                        struct extent_map_tree *em_tree;
+                        struct extent_map *em;
+
+                        em_tree = &root->fs_info->mapping_tree.map_tree;
+                        read_lock(&em_tree->lock);
+                        em = lookup_extent_mapping(em_tree, found_key.objectid,
+                                                   found_key.offset);
+                        read_unlock(&em_tree->lock);
+                        if (!em) {
+                                btrfs_err(root->fs_info,
+                        "logical %llu len %llu found bg but no related chunk",
+                                          found_key.objectid, found_key.offset);
+                                ret = -ENOENT;
+                        } else {
+                                ret = 0;
+                        }
                         goto out;
                 }
                 path->slots[0]++;