Commit ab474fcc authored by Gao Xiang's avatar Gao Xiang
Browse files

erofs: clean up z_erofs_extent_lookback 

Avoid the unnecessary tail recursion since it can be converted into
a loop directly in order to prevent potential stack overflow.

It's a pretty straightforward conversion.

Link: https://lore.kernel.org/r/20220310182743.102365-1-hsiangkao@linux.alibaba.com


Reviewed-by: default avatarYue Hu <huyue2@coolpad.com>
Reviewed-by: default avatarChao Yu <chao@kernel.org>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
parent d467e980

fs/erofs/zmap.c

+33 −34
Original line number Diff line number Diff line
@@ -431,20 +431,13 @@ static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m, 
				   unsigned int lookback_distance)

{

	struct erofs_inode *const vi = EROFS_I(m->inode);

	struct erofs_map_blocks *const map = m->map;

	const unsigned int lclusterbits = vi->z_logical_clusterbits;

	unsigned long lcn = m->lcn;

	int err;



	if (lcn < lookback_distance) {

		erofs_err(m->inode->i_sb,

			  "bogus lookback distance @ nid %llu", vi->nid);

		DBG_BUGON(1);

		return -EFSCORRUPTED;

	}

	while (m->lcn >= lookback_distance) {

		unsigned long lcn = m->lcn - lookback_distance;

		int err;



		/* load extent head logical cluster if needed */

	lcn -= lookback_distance;

		err = z_erofs_load_cluster_from_disk(m, lcn, false);

		if (err)

			return err;
@@ -458,13 +451,14 @@ static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m, 
				DBG_BUGON(1);

				return -EFSCORRUPTED;

			}

		return z_erofs_extent_lookback(m, m->delta[0]);

			lookback_distance = m->delta[0];

			continue;

		case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:

		case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:

		case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:

			m->headtype = m->type;

		map->m_la = (lcn << lclusterbits) | m->clusterofs;

		break;

			m->map->m_la = (lcn << lclusterbits) | m->clusterofs;

			return 0;

		default:

			erofs_err(m->inode->i_sb,

				  "unknown type %u @ lcn %lu of nid %llu",
@@ -472,7 +466,12 @@ static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m, 
			DBG_BUGON(1);

			return -EOPNOTSUPP;

		}

	return 0;

	}



	erofs_err(m->inode->i_sb, "bogus lookback distance @ nid %llu",

		  vi->nid);

	DBG_BUGON(1);

	return -EFSCORRUPTED;

}



static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,