btrfs: output more debug messages for uncommitted transaction

Print extra information about how many dirty bytes an uncommitted
has at the end of mount.

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

fs/btrfs/disk-io.c

@@ -4483,6 +4483,48 @@ int btrfs_commit_super(struct btrfs_fs_info *fs_info)
 	return btrfs_commit_transaction(trans);
 }
 
+static void warn_about_uncommitted_trans(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_transaction *trans;
+	struct btrfs_transaction *tmp;
+	bool found = false;
+
+	if (list_empty(&fs_info->trans_list))
+		return;
+
+	/*
+	 * This function is only called at the very end of close_ctree(),
+	 * thus no other running transaction, no need to take trans_lock.
+	 */
+	ASSERT(test_bit(BTRFS_FS_CLOSING_DONE, &fs_info->flags));
+	list_for_each_entry_safe(trans, tmp, &fs_info->trans_list, list) {
+		struct extent_state *cached = NULL;
+		u64 dirty_bytes = 0;
+		u64 cur = 0;
+		u64 found_start;
+		u64 found_end;
+
+		found = true;
+		while (!find_first_extent_bit(&trans->dirty_pages, cur,
+			&found_start, &found_end, EXTENT_DIRTY, &cached)) {
+			dirty_bytes += found_end + 1 - found_start;
+			cur = found_end + 1;
+		}
+		btrfs_warn(fs_info,
+	"transaction %llu (with %llu dirty metadata bytes) is not committed",
+			   trans->transid, dirty_bytes);
+		btrfs_cleanup_one_transaction(trans, fs_info);
+
+		if (trans == fs_info->running_transaction)
+			fs_info->running_transaction = NULL;
+		list_del_init(&trans->list);
+
+		btrfs_put_transaction(trans);
+		trace_btrfs_transaction_commit(fs_info);
+	}
+	ASSERT(!found);
+}
+
 void __cold close_ctree(struct btrfs_fs_info *fs_info)
 {
 	int ret;
@@ -4591,7 +4633,7 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
 	btrfs_stop_all_workers(fs_info);
 
 	/* We shouldn't have any transaction open at this point */
-	ASSERT(list_empty(&fs_info->trans_list));
+	warn_about_uncommitted_trans(fs_info);
 
 	clear_bit(BTRFS_FS_OPEN, &fs_info->flags);
 	free_root_pointers(fs_info, true);