kernel: mtdsplit_h3c_vfs: return 0 for non-fatal errors

Since Linux 6.7, introduced with commit 5c2f7727d437 ("mtd: mtdpart:
check for subpartitions parsing result"), errors during subpartition
parsing cause all MTD partitions to be torn down.

Since the current mtdsplit driver for devices using H3C VFS returns
-EINVAL if it does not find a file system containing an OpenWrt image,
this makes initial installation of OpenWrt impossible.

Work around this by returning 0 when the file system contains unexpected
data. Also print a message in this case to show what is going on.

Signed-off-by: Jan Hoffmann <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/19475
Signed-off-by: Hauke Mehrtens <[email protected]>

target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_h3c_vfs.c

@@ -98,8 +98,11 @@ static int mtdsplit_h3c_vfs_parse(struct mtd_info *mtd,
 	if (retlen != sizeof(format_flag))
 		return -EIO;
 
-	if (format_flag != FORMAT_FLAG)
-		return -EINVAL;
+	if (format_flag != FORMAT_FLAG) {
+		pr_info("mtdsplit_h3c_vfs: unexpected format flag %08x\n",
+			format_flag);
+		return 0;
+	}
 
 	/* Check file entry */
 	err = mtd_read(mtd, FILE_ENTRY_OFFSET, sizeof(file_entry), &retlen,
@@ -110,20 +113,14 @@ static int mtdsplit_h3c_vfs_parse(struct mtd_info *mtd,
 	if (retlen != sizeof(file_entry))
 		return -EIO;
 
-	if (file_entry.flags != FILE_ENTRY_FLAGS)
-		return -EINVAL;
-
-	if (file_entry.parent_block != FILE_ENTRY_PARENT_BLOCK)
-		return -EINVAL;
-
-	if (file_entry.parent_index != FILE_ENTRY_PARENT_INDEX)
-		return -EINVAL;
-
-	if (file_entry.data_block != FILE_ENTRY_DATA_BLOCK)
-		return -EINVAL;
-
-	if (strncmp(file_entry.name, FILE_ENTRY_NAME, sizeof(file_entry.name)) != 0)
-		return -EINVAL;
+	if (file_entry.flags != FILE_ENTRY_FLAGS ||
+	    file_entry.parent_block != FILE_ENTRY_PARENT_BLOCK ||
+	    file_entry.parent_index != FILE_ENTRY_PARENT_INDEX ||
+	    file_entry.data_block != FILE_ENTRY_DATA_BLOCK ||
+	    strncmp(file_entry.name, FILE_ENTRY_NAME, sizeof(file_entry.name)) != 0) {
+		pr_info("mtdsplit_h3c_vfs: unexpected file entry - OpenWrt probably not installed\n");
+		return 0;
+	}
 
 	/* Find rootfs offset */
 	kernel_size = block_offset(file_entry.data_block +