erofs: simplify erofs_read_inode()

After commit 1c7f49a7 ("erofs: tidy up EROFS on-disk naming"),
there is a unique `union erofs_inode_i_u` so that we could parse
the union directly.

Besides, it also replaces `inode->i_sb` with `sb` for simplicity.
Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20231109111822.17944-1-mengferry@linux.alibaba.comSigned-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

fs/erofs/inode.c

@@ -15,11 +15,11 @@ static void *erofs_read_inode(struct erofs_buf *buf,
 	struct erofs_sb_info *sbi = EROFS_SB(sb);
 	struct erofs_inode *vi = EROFS_I(inode);
 	const erofs_off_t inode_loc = erofs_iloc(inode);
-
 	erofs_blk_t blkaddr, nblks = 0;
 	void *kaddr;
 	struct erofs_inode_compact *dic;
 	struct erofs_inode_extended *die, *copied = NULL;
+	union erofs_inode_i_u iu;
 	unsigned int ifmt;
 	int err;
 
@@ -35,9 +35,8 @@ static void *erofs_read_inode(struct erofs_buf *buf,
 
 	dic = kaddr + *ofs;
 	ifmt = le16_to_cpu(dic->i_format);
-
 	if (ifmt & ~EROFS_I_ALL) {
-		erofs_err(inode->i_sb, "unsupported i_format %u of nid %llu",
+		erofs_err(sb, "unsupported i_format %u of nid %llu",
 			  ifmt, vi->nid);
 		err = -EOPNOTSUPP;
 		goto err_out;
@@ -45,7 +44,7 @@ static void *erofs_read_inode(struct erofs_buf *buf,
 
 	vi->datalayout = erofs_inode_datalayout(ifmt);
 	if (vi->datalayout >= EROFS_INODE_DATALAYOUT_MAX) {
-		erofs_err(inode->i_sb, "unsupported datalayout %u of nid %llu",
+		erofs_err(sb, "unsupported datalayout %u of nid %llu",
 			  vi->datalayout, vi->nid);
 		err = -EOPNOTSUPP;
 		goto err_out;
@@ -82,40 +81,15 @@ static void *erofs_read_inode(struct erofs_buf *buf,
 		vi->xattr_isize = erofs_xattr_ibody_size(die->i_xattr_icount);
 
 		inode->i_mode = le16_to_cpu(die->i_mode);
-		switch (inode->i_mode & S_IFMT) {
-		case S_IFREG:
-		case S_IFDIR:
-		case S_IFLNK:
-			vi->raw_blkaddr = le32_to_cpu(die->i_u.raw_blkaddr);
-			break;
-		case S_IFCHR:
-		case S_IFBLK:
-			inode->i_rdev =
-				new_decode_dev(le32_to_cpu(die->i_u.rdev));
-			break;
-		case S_IFIFO:
-		case S_IFSOCK:
-			inode->i_rdev = 0;
-			break;
-		default:
-			goto bogusimode;
-		}
+		iu = die->i_u;
 		i_uid_write(inode, le32_to_cpu(die->i_uid));
 		i_gid_write(inode, le32_to_cpu(die->i_gid));
 		set_nlink(inode, le32_to_cpu(die->i_nlink));
-
-		/* extended inode has its own timestamp */
+		/* each extended inode has its own timestamp */
 		inode_set_ctime(inode, le64_to_cpu(die->i_mtime),
 				le32_to_cpu(die->i_mtime_nsec));
 
 		inode->i_size = le64_to_cpu(die->i_size);
-
-		/* total blocks for compressed files */
-		if (erofs_inode_is_data_compressed(vi->datalayout))
-			nblks = le32_to_cpu(die->i_u.compressed_blocks);
-		else if (vi->datalayout == EROFS_INODE_CHUNK_BASED)
-			/* fill chunked inode summary info */
-			vi->chunkformat = le16_to_cpu(die->i_u.c.format);
 		kfree(copied);
 		copied = NULL;
 		break;
@@ -125,49 +99,51 @@ static void *erofs_read_inode(struct erofs_buf *buf,
 		vi->xattr_isize = erofs_xattr_ibody_size(dic->i_xattr_icount);
 
 		inode->i_mode = le16_to_cpu(dic->i_mode);
+		iu = dic->i_u;
+		i_uid_write(inode, le16_to_cpu(dic->i_uid));
+		i_gid_write(inode, le16_to_cpu(dic->i_gid));
+		set_nlink(inode, le16_to_cpu(dic->i_nlink));
+		/* use build time for compact inodes */
+		inode_set_ctime(inode, sbi->build_time, sbi->build_time_nsec);
+
+		inode->i_size = le32_to_cpu(dic->i_size);
+		break;
+	default:
+		erofs_err(sb, "unsupported on-disk inode version %u of nid %llu",
+			  erofs_inode_version(ifmt), vi->nid);
+		err = -EOPNOTSUPP;
+		goto err_out;
+	}
+
 	switch (inode->i_mode & S_IFMT) {
 	case S_IFREG:
 	case S_IFDIR:
 	case S_IFLNK:
-			vi->raw_blkaddr = le32_to_cpu(dic->i_u.raw_blkaddr);
+		vi->raw_blkaddr = le32_to_cpu(iu.raw_blkaddr);
 		break;
 	case S_IFCHR:
 	case S_IFBLK:
-			inode->i_rdev =
-				new_decode_dev(le32_to_cpu(dic->i_u.rdev));
+		inode->i_rdev = new_decode_dev(le32_to_cpu(iu.rdev));
 		break;
 	case S_IFIFO:
 	case S_IFSOCK:
 		inode->i_rdev = 0;
 		break;
 	default:
-			goto bogusimode;
-		}
-		i_uid_write(inode, le16_to_cpu(dic->i_uid));
-		i_gid_write(inode, le16_to_cpu(dic->i_gid));
-		set_nlink(inode, le16_to_cpu(dic->i_nlink));
-
-		/* use build time for compact inodes */
-		inode_set_ctime(inode, sbi->build_time, sbi->build_time_nsec);
-
-		inode->i_size = le32_to_cpu(dic->i_size);
-		if (erofs_inode_is_data_compressed(vi->datalayout))
-			nblks = le32_to_cpu(dic->i_u.compressed_blocks);
-		else if (vi->datalayout == EROFS_INODE_CHUNK_BASED)
-			vi->chunkformat = le16_to_cpu(dic->i_u.c.format);
-		break;
-	default:
-		erofs_err(inode->i_sb,
-			  "unsupported on-disk inode version %u of nid %llu",
-			  erofs_inode_version(ifmt), vi->nid);
-		err = -EOPNOTSUPP;
+		erofs_err(sb, "bogus i_mode (%o) @ nid %llu", inode->i_mode,
+			  vi->nid);
+		err = -EFSCORRUPTED;
 		goto err_out;
 	}
 
-	if (vi->datalayout == EROFS_INODE_CHUNK_BASED) {
+	/* total blocks for compressed files */
+	if (erofs_inode_is_data_compressed(vi->datalayout)) {
+		nblks = le32_to_cpu(iu.compressed_blocks);
+	} else if (vi->datalayout == EROFS_INODE_CHUNK_BASED) {
+		/* fill chunked inode summary info */
+		vi->chunkformat = le16_to_cpu(iu.c.format);
 		if (vi->chunkformat & ~EROFS_CHUNK_FORMAT_ALL) {
-			erofs_err(inode->i_sb,
-				  "unsupported chunk format %x of nid %llu",
+			erofs_err(sb, "unsupported chunk format %x of nid %llu",
 				  vi->chunkformat, vi->nid);
 			err = -EOPNOTSUPP;
 			goto err_out;
@@ -191,10 +167,6 @@ static void *erofs_read_inode(struct erofs_buf *buf,
 		inode->i_blocks = nblks << (sb->s_blocksize_bits - 9);
 	return kaddr;
 
-bogusimode:
-	erofs_err(inode->i_sb, "bogus i_mode (%o) @ nid %llu",
-		  inode->i_mode, vi->nid);
-	err = -EFSCORRUPTED;
 err_out:
 	DBG_BUGON(1);
 	kfree(copied);