ext4 crypto: fail the mount if blocksize != pagesize

We currently don't correctly handle the case where blocksize !=
pagesize, so disallow the mount in those cases.
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -4065,7 +4065,15 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		}
 	}
 
-	if (unlikely(sbi->s_mount_flags & EXT4_MF_TEST_DUMMY_ENCRYPTION) &&
+	if ((DUMMY_ENCRYPTION_ENABLED(sbi) ||
+	     EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_ENCRYPT)) &&
+	    (blocksize != PAGE_CACHE_SIZE)) {
+		ext4_msg(sb, KERN_ERR,
+			 "Unsupported blocksize for fs encryption");
+		goto failed_mount_wq;
+	}
+
+	if (DUMMY_ENCRYPTION_ENABLED(sbi) &&
 	    !(sb->s_flags & MS_RDONLY) &&
 	    !EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_ENCRYPT)) {
 		EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_ENCRYPT);