1 files changed, 19 insertions, 0 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index add4af641cfa..cf8983e4a2eb 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3768,6 +3768,25 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
                 }
                 if (!ret) {
                         ret = write_one_cache_group(trans, root, path, cache);
+                        /*
+                         * One of the free space endio workers might have
+                         * created a new block group while updating a free space
+                         * cache's inode (at inode.c:btrfs_finish_ordered_io())
+                         * and hasn't released its transaction handle yet, in
+                         * which case the new block group is still attached to
+                         * its transaction handle and its creation has not
+                         * finished yet (no block group item in the extent tree
+                         * yet, etc). If this is the case, wait for all free
+                         * space endio workers to finish and retry. This is a
+                         * a very rare case so no need for a more efficient and
+                         * complex approach.
+                         */
+                        if (ret == -ENOENT) {
+                                wait_event(cur_trans->writer_wait,
+                                   atomic_read(&cur_trans->num_writers) == 1);
+                                ret = write_one_cache_group(trans, root, path,
+                                                            cache);
+                        }
                         if (ret)
                                 btrfs_abort_transaction(trans, root, ret);
                 }