erofs: clean up z_erofs_load_full_lcluster()

Only four lcluster types here, remove redundant code.
No real logic changes.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240508123357.3266173-1-hsiangkao@linux.alibaba.com

Author: hsiangkao

fs/erofs/erofs_fs.h

@@ -396,8 +396,7 @@ enum {
 	Z_EROFS_LCLUSTER_TYPE_MAX
 };
 
-#define Z_EROFS_LI_LCLUSTER_TYPE_BITS        2
-#define Z_EROFS_LI_LCLUSTER_TYPE_BIT         0
+#define Z_EROFS_LI_LCLUSTER_TYPE_MASK	(Z_EROFS_LCLUSTER_TYPE_MAX - 1)
 
 /* (noncompact only, HEAD) This pcluster refers to partial decompressed data */
 #define Z_EROFS_LI_PARTIAL_REF		(1 << 15)
@@ -451,8 +450,6 @@ static inline void erofs_check_ondisk_layout_definitions(void)
 		     sizeof(struct z_erofs_lcluster_index));
 	BUILD_BUG_ON(sizeof(struct erofs_deviceslot) != 128);
 
-	BUILD_BUG_ON(BIT(Z_EROFS_LI_LCLUSTER_TYPE_BITS) <
-		     Z_EROFS_LCLUSTER_TYPE_MAX - 1);
 	/* exclude old compiler versions like gcc 7.5.0 */
 	BUILD_BUG_ON(__builtin_constant_p(fmh) ?
 		     fmh != cpu_to_le64(1ULL << 63) : 0);

fs/erofs/zmap.c

@@ -31,7 +31,7 @@ static int z_erofs_load_full_lcluster(struct z_erofs_maprecorder *m,
 			vi->inode_isize + vi->xattr_isize) +
 			lcn * sizeof(struct z_erofs_lcluster_index);
 	struct z_erofs_lcluster_index *di;
-	unsigned int advise, type;
+	unsigned int advise;
 
 	m->kaddr = erofs_read_metabuf(&m->map->buf, inode->i_sb,
 				      erofs_blknr(inode->i_sb, pos), EROFS_KMAP);
@@ -43,10 +43,8 @@ static int z_erofs_load_full_lcluster(struct z_erofs_maprecorder *m,
 	di = m->kaddr + erofs_blkoff(inode->i_sb, pos);
 
 	advise = le16_to_cpu(di->di_advise);
-	type = (advise >> Z_EROFS_LI_LCLUSTER_TYPE_BIT) &
-		((1 << Z_EROFS_LI_LCLUSTER_TYPE_BITS) - 1);
-	switch (type) {
-	case Z_EROFS_LCLUSTER_TYPE_NONHEAD:
+	m->type = advise & Z_EROFS_LI_LCLUSTER_TYPE_MASK;
+	if (m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
 		m->clusterofs = 1 << vi->z_logical_clusterbits;
 		m->delta[0] = le16_to_cpu(di->di_u.delta[0]);
 		if (m->delta[0] & Z_EROFS_LI_D0_CBLKCNT) {
@@ -60,24 +58,15 @@ static int z_erofs_load_full_lcluster(struct z_erofs_maprecorder *m,
 			m->delta[0] = 1;
 		}
 		m->delta[1] = le16_to_cpu(di->di_u.delta[1]);
-		break;
-	case Z_EROFS_LCLUSTER_TYPE_PLAIN:
-	case Z_EROFS_LCLUSTER_TYPE_HEAD1:
-	case Z_EROFS_LCLUSTER_TYPE_HEAD2:
-		if (advise & Z_EROFS_LI_PARTIAL_REF)
-			m->partialref = true;
+	} else {
+		m->partialref = !!(advise & Z_EROFS_LI_PARTIAL_REF);
 		m->clusterofs = le16_to_cpu(di->di_clusterofs);
 		if (m->clusterofs >= 1 << vi->z_logical_clusterbits) {
 			DBG_BUGON(1);
 			return -EFSCORRUPTED;
 		}
 		m->pblk = le32_to_cpu(di->di_u.blkaddr);
-		break;
-	default:
-		DBG_BUGON(1);
-		return -EOPNOTSUPP;
 	}
-	m->type = type;
 	return 0;
 }