[PATCH 3.16 48/61] ext4: Make checks for metadata_csum feature safer

[Ben Hutchings]

3.16.85-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Tahsin Erdogan <tahsin@xxxxxxxxxx>

This is just a small part of commit dec214d00e0d7 "ext4: xattr inode
deduplication" that makes checks for metadata_csum feature safer and is
actually needed by following fixes.

Signed-off-by: Tahsin Erdogan <tahsin@xxxxxxxxxx>
Acked-by: Jan Kara <jack@xxxxxxx>
[bwh: Ported to 3.16: Use EXT4_HAS_RO_COMPAT_FEATURE()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2411,21 +2411,24 @@ extern void ext4_group_desc_csum_set(str
 extern int ext4_register_li_request(struct super_block *sb,
 				    ext4_group_t first_not_zeroed);
 
-static inline int ext4_has_group_desc_csum(struct super_block *sb)
-{
-	return EXT4_HAS_RO_COMPAT_FEATURE(sb,
-					  EXT4_FEATURE_RO_COMPAT_GDT_CSUM) ||
-	       (EXT4_SB(sb)->s_chksum_driver != NULL);
-}
-
 static inline int ext4_has_metadata_csum(struct super_block *sb)
 {
 	WARN_ON_ONCE(EXT4_HAS_RO_COMPAT_FEATURE(sb,
 			EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) &&
 		     !EXT4_SB(sb)->s_chksum_driver);
 
-	return (EXT4_SB(sb)->s_chksum_driver != NULL);
+	return EXT4_HAS_RO_COMPAT_FEATURE(sb,
+			EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) &&
+	       (EXT4_SB(sb)->s_chksum_driver != NULL);
+}
+
+static inline int ext4_has_group_desc_csum(struct super_block *sb)
+{
+	return EXT4_HAS_RO_COMPAT_FEATURE(sb,
+					  EXT4_FEATURE_RO_COMPAT_GDT_CSUM) ||
+		ext4_has_metadata_csum(sb);
 }
+
 static inline ext4_fsblk_t ext4_blocks_count(struct ext4_super_block *es)
 {
 	return ((ext4_fsblk_t)le32_to_cpu(es->s_blocks_count_hi) << 32) |