btrfs: do not BUG_ON() on tree mod log failure at __btrfs_cow_block()

At __btrfs_cow_block(), instead of doing a BUG_ON() in case we fail to
record a tree mod log root insertion operation, do a transaction abort
instead. There's really no need for the BUG_ON(), we can properly
release all resources in this context and turn the filesystem to RO mode
and in an error state instead.

CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 8496535..d6c2956 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -584,9 +584,14 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
                    btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
                        parent_start = buf->start;
 
-               atomic_inc(&cow->refs);
                ret = btrfs_tree_mod_log_insert_root(root->node, cow, true);
-               BUG_ON(ret < 0);
+               if (ret < 0) {
+                       btrfs_tree_unlock(cow);
+                       free_extent_buffer(cow);
+                       btrfs_abort_transaction(trans, ret);
+                       return ret;
+               }
+               atomic_inc(&cow->refs);
                rcu_assign_pointer(root->node, cow);
 
                btrfs_free_tree_block(trans, btrfs_root_id(root), buf,