bcache: check unsupported feature sets for bcache register

This patch adds the check for features which is incompatible for
current supported feature sets.

Now if the bcache device created by bcache-tools has features that
current kernel doesn't support, read_super() will fail with error
messoage. E.g. if an unsupported incompatible feature detected,
bcache register will fail with dmesg "bcache: register_bcache() error :
Unsupported incompatible feature found".

Fixes: d721a43 ("bcache: increase super block version for cache device and backing device")
Fixes: ffa4703 ("bcache: add bucket_size_hi into struct cache_sb_disk for large bucket")
Signed-off-by: Coly Li <[email protected]>
Cc: [email protected] # 5.9+
Signed-off-by: Jens Axboe <[email protected]>

drivers/md/bcache/features.h

@@ -79,6 +79,21 @@ static inline void bch_clear_feature_##name(struct cache_sb *sb) \
 
 BCH_FEATURE_INCOMPAT_FUNCS(large_bucket, LARGE_BUCKET);
 
+static inline bool bch_has_unknown_compat_features(struct cache_sb *sb)
+{
+	return ((sb->feature_compat & ~BCH_FEATURE_COMPAT_SUPP) != 0);
+}
+
+static inline bool bch_has_unknown_ro_compat_features(struct cache_sb *sb)
+{
+	return ((sb->feature_ro_compat & ~BCH_FEATURE_RO_COMPAT_SUPP) != 0);
+}
+
+static inline bool bch_has_unknown_incompat_features(struct cache_sb *sb)
+{
+	return ((sb->feature_incompat & ~BCH_FEATURE_INCOMPAT_SUPP) != 0);
+}
+
 int bch_print_cache_set_feature_compat(struct cache_set *c, char *buf, int size);
 int bch_print_cache_set_feature_ro_compat(struct cache_set *c, char *buf, int size);
 int bch_print_cache_set_feature_incompat(struct cache_set *c, char *buf, int size);

drivers/md/bcache/super.c

@@ -228,6 +228,20 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
 		sb->feature_compat = le64_to_cpu(s->feature_compat);
 		sb->feature_incompat = le64_to_cpu(s->feature_incompat);
 		sb->feature_ro_compat = le64_to_cpu(s->feature_ro_compat);
+
+		/* Check incompatible features */
+		err = "Unsupported compatible feature found";
+		if (bch_has_unknown_compat_features(sb))
+			goto err;
+
+		err = "Unsupported read-only compatible feature found";
+		if (bch_has_unknown_ro_compat_features(sb))
+			goto err;
+
+		err = "Unsupported incompatible feature found";
+		if (bch_has_unknown_incompat_features(sb))
+			goto err;
+
 		err = read_super_common(sb, bdev, s);
 		if (err)
 			goto err;