1 files changed, 18 insertions, 0 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 171312d51799..07204bf601ed 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4227,6 +4227,24 @@ out:
         space_info->chunk_alloc = 0;
         spin_unlock(&space_info->lock);
         mutex_unlock(&fs_info->chunk_mutex);
+        /*
+         * When we allocate a new chunk we reserve space in the chunk block
+         * reserve to make sure we can COW nodes/leafs in the chunk tree or
+         * add new nodes/leafs to it if we end up needing to do it when
+         * inserting the chunk item and updating device items as part of the
+         * second phase of chunk allocation, performed by
+         * btrfs_finish_chunk_alloc(). So make sure we don't accumulate a
+         * large number of new block groups to create in our transaction
+         * handle's new_bgs list to avoid exhausting the chunk block reserve
+         * in extreme cases - like having a single transaction create many new
+         * block groups when starting to write out the free space caches of all
+         * the block groups that were made dirty during the lifetime of the
+         * transaction.
+         */
+        if (trans->chunk_bytes_reserved >= (2 * 1024 * 1024ull)) {
+                btrfs_create_pending_block_groups(trans, trans->root);
+                btrfs_trans_release_chunk_metadata(trans);
+        }
         return ret;
 }