fs/ext2: Ignore checksum seed incompat feature

This incompat feature is used to denote that the filesystem stored its
metadata checksum seed in the superblock. This is used to allow tune2fs
changing the UUID on a mounted metdata_csum filesystem without having
to rewrite all the disk metadata. However, the GRUB doesn't use the
metadata checksum at all. So, it can just ignore this feature if it
is enabled. This is consistent with the GRUB filesystem code in general
which just does a best effort to access the filesystem's data.

The checksum seed incompat feature has to be removed from the ignore
list if the support for metadata checksum verification is added to the
GRUB ext2 driver later.

Suggested-by: Eric Sandeen <esandeen@redhat.com>
Suggested-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/fs/ext2.c b/grub-core/fs/ext2.c
index e7dd78e66358138bb1496bd3d036182787b6b49e..4953a1591c33950250bcf8bfc9f50f00e670ceaa 100644 (file)
--- a/grub-core/fs/ext2.c
+++ b/grub-core/fs/ext2.c
@@ -103,6 +103,7 @@ GRUB_MOD_LICENSE ("GPLv3+");
 #define EXT4_FEATURE_INCOMPAT_64BIT            0x0080
 #define EXT4_FEATURE_INCOMPAT_MMP              0x0100
 #define EXT4_FEATURE_INCOMPAT_FLEX_BG          0x0200
+#define EXT4_FEATURE_INCOMPAT_CSUM_SEED                0x2000
 #define EXT4_FEATURE_INCOMPAT_ENCRYPT          0x10000
 
 /* The set of back-incompatible features this driver DOES support. Add (OR)
@@ -123,10 +124,15 @@ GRUB_MOD_LICENSE ("GPLv3+");
  * mmp:            Not really back-incompatible - was added as such to
  *                 avoid multiple read-write mounts. Safe to ignore for this
  *                 RO driver.
+ * checksum seed:  Not really back-incompatible - was added to allow tools
+ *                 such as tune2fs to change the UUID on a mounted metadata
+ *                 checksummed filesystem. Safe to ignore for now since the
+ *                 driver doesn't support checksum verification. However, it
+ *                 has to be removed from this list if the support is added later.
  */
 #define EXT2_DRIVER_IGNORED_INCOMPAT ( EXT3_FEATURE_INCOMPAT_RECOVER \
-                                    | EXT4_FEATURE_INCOMPAT_MMP)
-
+                                    | EXT4_FEATURE_INCOMPAT_MMP \
+                                    | EXT4_FEATURE_INCOMPAT_CSUM_SEED)
 
 #define EXT3_JOURNAL_MAGIC_NUMBER      0xc03b3998U