btrfs: compare the correct fsid/metadata_uuid in btrfs_validate_super

The function btrfs_validate_super() should verify the metadata_uuid in
the provided superblock argument. Because, all its callers expect it to
do that.

Such as in the following stacks:

  write_all_supers()
   sb = fs_info->super_for_commit;
   btrfs_validate_write_super(.., sb)
     btrfs_validate_super(.., sb, ..)

  scrub_one_super()
	btrfs_validate_super(.., sb, ..)

And
   check_dev_super()
	btrfs_validate_super(.., sb, ..)

However, it currently verifies the fs_info::super_copy::metadata_uuid
instead.  Fix this using the correct metadata_uuid in the superblock
argument.

CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: asj

fs/btrfs/disk-io.c

@@ -2391,13 +2391,11 @@ int btrfs_validate_super(struct btrfs_fs_info *fs_info,
 		ret = -EINVAL;
 	}
 
-	if (btrfs_fs_incompat(fs_info, METADATA_UUID) &&
-	    memcmp(fs_info->fs_devices->metadata_uuid,
-		   fs_info->super_copy->metadata_uuid, BTRFS_FSID_SIZE)) {
+	if (memcmp(fs_info->fs_devices->metadata_uuid, btrfs_sb_fsid_ptr(sb),
+		   BTRFS_FSID_SIZE) != 0) {
 		btrfs_err(fs_info,
 "superblock metadata_uuid doesn't match metadata uuid of fs_devices: %pU != %pU",
-			fs_info->super_copy->metadata_uuid,
-			fs_info->fs_devices->metadata_uuid);
+			  btrfs_sb_fsid_ptr(sb), fs_info->fs_devices->metadata_uuid);
 		ret = -EINVAL;
 	}