1 files changed, 35 insertions, 36 deletions

diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 361b1d6e4bf9..572f0b8151ba 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -431,48 +431,47 @@ 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;
+		/* load extent head logical cluster if needed */
+		err = z_erofs_load_cluster_from_disk(m, lcn, false);
+		if (err)
+			return err;
 
-	switch (m->type) {
-	case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
-		if (!m->delta[0]) {
+		switch (m->type) {
+		case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
+			if (!m->delta[0]) {
+				erofs_err(m->inode->i_sb,
+					  "invalid lookback distance 0 @ nid %llu",
+					  vi->nid);
+				DBG_BUGON(1);
+				return -EFSCORRUPTED;
+			}
+			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;
+			m->map->m_la = (lcn << lclusterbits) | m->clusterofs;
+			return 0;
+		default:
 			erofs_err(m->inode->i_sb,
-				  "invalid lookback distance 0 @ nid %llu",
-				  vi->nid);
+				  "unknown type %u @ lcn %lu of nid %llu",
+				  m->type, lcn, vi->nid);
 			DBG_BUGON(1);
-			return -EFSCORRUPTED;
+			return -EOPNOTSUPP;
 		}
-		return z_erofs_extent_lookback(m, m->delta[0]);
-	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;
-	default:
-		erofs_err(m->inode->i_sb,
-			  "unknown type %u @ lcn %lu of nid %llu",
-			  m->type, lcn, vi->nid);
-		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,
@@ -494,7 +493,7 @@ static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
 	     !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1)) ||
 	    ((m->headtype == Z_EROFS_VLE_CLUSTER_TYPE_HEAD2) &&
 	     !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_2))) {
-		map->m_plen = 1 << lclusterbits;
+		map->m_plen = 1ULL << lclusterbits;
 		return 0;
 	}
 	lcn = m->lcn + 1;
@@ -540,7 +539,7 @@ static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
 		return -EFSCORRUPTED;
 	}
 out:
-	map->m_plen = m->compressedlcs << lclusterbits;
+	map->m_plen = (u64)m->compressedlcs << lclusterbits;
 	return 0;
 err_bonus_cblkcnt:
 	erofs_err(m->inode->i_sb,