ext4: Replace open coded mdata csum feature to helper function

commit 9aa5d32ba269bec0e7eaba2697a986a7b0bc8528 upstream.

Besides the fact that this replacement improves code readability
it also protects from errors caused direct EXT4_S(sb)->s_es manipulation
which may result attempt to use uninitialized  csum machinery.

#Testcase_BEGIN
IMG=/dev/ram0
MNT=/mnt
mkfs.ext4 $IMG
mount $IMG $MNT
#Enable feature directly on disk, on mounted fs
tune2fs -O metadata_csum  $IMG
# Provoke metadata update, likey result in OOPS
touch $MNT/test
umount $MNT
#Testcase_END

# Replacement script
@@
expression E;
@@
- EXT4_HAS_RO_COMPAT_FEATURE(E, EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)
+ ext4_has_metadata_csum(E)

https://bugzilla.kernel.org/show_bug.cgi?id=82201

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 4eca63f8314a..bd5f351ef10b 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2328,6 +2328,14 @@ static inline int ext4_has_group_desc_csum(struct super_block *sb)
 					  EXT4_FEATURE_RO_COMPAT_METADATA_CSUM);
 }
 
+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);
+}
 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) |