Commit 18dc22c1 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: Add WARN_ON for qgroup reserved underflow 



Goldwyn Rodrigues has exposed and fixed a bug which underflows btrfs
qgroup reserved space, and leads to non-writable fs.

This reminds us that we don't have enough underflow check for qgroup
reserved space.

For underflow case, we should not really underflow the numbers but warn
and keeps qgroup still work.

So add more check on qgroup reserved space and add WARN_ON() and
btrfs_warn() for any underflow case.

Signed-off-by: default avatarQu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Reviewed-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 7089db84

fs/btrfs/qgroup.c

+26 −5
Original line number Diff line number Diff line
@@ -1038,6 +1038,15 @@ static void qgroup_dirty(struct btrfs_fs_info *fs_info, 
		list_add(&qgroup->dirty, &fs_info->dirty_qgroups);

}



static void report_reserved_underflow(struct btrfs_fs_info *fs_info,

				      struct btrfs_qgroup *qgroup,

				      u64 num_bytes)

{

	btrfs_warn(fs_info,

		"qgroup %llu reserved space underflow, have: %llu, to free: %llu",

		qgroup->qgroupid, qgroup->reserved, num_bytes);

	qgroup->reserved = 0;

}

/*

 * The easy accounting, if we are adding/removing the only ref for an extent

 * then this qgroup and all of the parent qgroups get their reference and
@@ -1065,8 +1074,12 @@ static int __qgroup_excl_accounting(struct btrfs_fs_info *fs_info, 
	WARN_ON(sign < 0 && qgroup->excl < num_bytes);

	qgroup->excl += sign * num_bytes;

	qgroup->excl_cmpr += sign * num_bytes;

	if (sign > 0)

	if (sign > 0) {

		if (WARN_ON(qgroup->reserved < num_bytes))

			report_reserved_underflow(fs_info, qgroup, num_bytes);

		else

			qgroup->reserved -= num_bytes;

	}



	qgroup_dirty(fs_info, qgroup);
@@ -1086,8 +1099,13 @@ static int __qgroup_excl_accounting(struct btrfs_fs_info *fs_info, 
		qgroup->rfer_cmpr += sign * num_bytes;

		WARN_ON(sign < 0 && qgroup->excl < num_bytes);

		qgroup->excl += sign * num_bytes;

		if (sign > 0)

		if (sign > 0) {

			if (WARN_ON(qgroup->reserved < num_bytes))

				report_reserved_underflow(fs_info, qgroup,

							  num_bytes);

			else

				qgroup->reserved -= num_bytes;

		}

		qgroup->excl_cmpr += sign * num_bytes;

		qgroup_dirty(fs_info, qgroup);
@@ -2424,6 +2442,9 @@ void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info, 


		qg = unode_aux_to_qgroup(unode);



		if (WARN_ON(qg->reserved < num_bytes))

			report_reserved_underflow(fs_info, qg, num_bytes);

		else

			qg->reserved -= num_bytes;



		list_for_each_entry(glist, &qg->groups, next_group) {

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