bcache: increase super block version for cache device and backing device

The new added super block version BCACHE_SB_VERSION_BDEV_WITH_FEATURES
(5) BCACHE_SB_VERSION_CDEV_WITH_FEATURES value (6), is for the feature
set bits.

Devices have super block version equal to the new version will have
three new members for feature set bits in the on-disk super block,
        __le64                  feature_compat;
        __le64                  feature_incompat;
        __le64                  feature_ro_compat;

They are used for further new features which may introduce on-disk
format change, and avoid unncessary super block version increase.

The very basic features handling code skeleton is also initialized in
this patch.

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 107 insertions, 3 deletions

diff --git a/drivers/md/bcache/features.h b/drivers/md/bcache/features.h
new file mode 100644
index 000000000000..ae7df37b9862
--- /dev/null
+++ b/drivers/md/bcache/features.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _BCACHE_FEATURES_H
+#define _BCACHE_FEATURES_H
+
+#include <linux/bcache.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+#define BCH_FEATURE_COMPAT		0
+#define BCH_FEATURE_RO_COMPAT		1
+#define BCH_FEATURE_INCOMPAT		2
+#define BCH_FEATURE_TYPE_MASK		0x03
+
+#define BCH_FEATURE_COMPAT_SUUP		0
+#define BCH_FEATURE_RO_COMPAT_SUUP	0
+#define BCH_FEATURE_INCOMPAT_SUUP	0
+
+#define BCH_HAS_COMPAT_FEATURE(sb, mask) \
+		((sb)->feature_compat & (mask))
+#define BCH_HAS_RO_COMPAT_FEATURE(sb, mask) \
+		((sb)->feature_ro_compat & (mask))
+#define BCH_HAS_INCOMPAT_FEATURE(sb, mask) \
+		((sb)->feature_incompat & (mask))
+
+/* Feature set definition */
+
+#define BCH_FEATURE_COMPAT_FUNCS(name, flagname) \
+static inline int bch_has_feature_##name(struct cache_sb *sb) \
+{ \
+	return (((sb)->feature_compat & \
+		BCH##_FEATURE_COMPAT_##flagname) != 0); \
+} \
+static inline void bch_set_feature_##name(struct cache_sb *sb) \
+{ \
+	(sb)->feature_compat |= \
+		BCH##_FEATURE_COMPAT_##flagname; \
+} \
+static inline void bch_clear_feature_##name(struct cache_sb *sb) \
+{ \
+	(sb)->feature_compat &= \
+		~BCH##_FEATURE_COMPAT_##flagname; \
+}
+
+#define BCH_FEATURE_RO_COMPAT_FUNCS(name, flagname) \
+static inline int bch_has_feature_##name(struct cache_sb *sb) \
+{ \
+	return (((sb)->feature_ro_compat & \
+		BCH##_FEATURE_RO_COMPAT_##flagname) != 0); \
+} \
+static inline void bch_set_feature_##name(struct cache_sb *sb) \
+{ \
+	(sb)->feature_ro_compat |= \
+		BCH##_FEATURE_RO_COMPAT_##flagname; \
+} \
+static inline void bch_clear_feature_##name(struct cache_sb *sb) \
+{ \
+	(sb)->feature_ro_compat &= \
+		~BCH##_FEATURE_RO_COMPAT_##flagname; \
+}
+
+#define BCH_FEATURE_INCOMPAT_FUNCS(name, flagname) \
+static inline int bch_has_feature_##name(struct cache_sb *sb) \
+{ \
+	return (((sb)->feature_incompat & \
+		BCH##_FEATURE_INCOMPAT_##flagname) != 0); \
+} \
+static inline void bch_set_feature_##name(struct cache_sb *sb) \
+{ \
+	(sb)->feature_incompat |= \
+		BCH##_FEATURE_INCOMPAT_##flagname; \
+} \
+static inline void bch_clear_feature_##name(struct cache_sb *sb) \
+{ \
+	(sb)->feature_incompat &= \
+		~BCH##_FEATURE_INCOMPAT_##flagname; \
+}
+
+#endif
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 40fb18028c01..c6ef410a21a8 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -13,6 +13,7 @@
 #include "extents.h"
 #include "request.h"
 #include "writeback.h"
+#include "features.h"
 
 #include <linux/blkdev.h>
 #include <linux/debugfs.h>
@@ -194,6 +195,7 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
 		sb->data_offset	= BDEV_DATA_START_DEFAULT;
 		break;
 	case BCACHE_SB_VERSION_BDEV_WITH_OFFSET:
+	case BCACHE_SB_VERSION_BDEV_WITH_FEATURES:
 		sb->data_offset	= le64_to_cpu(s->data_offset);
 
 		err = "Bad data offset";
@@ -207,6 +209,14 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
 		if (err)
 			goto err;
 		break;
+	case BCACHE_SB_VERSION_CDEV_WITH_FEATURES:
+		err = read_super_common(sb, bdev, s);
+		if (err)
+			goto err;
+		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);
+		break;
 	default:
 		err = "Unsupported superblock version";
 		goto err;
@@ -241,7 +251,6 @@ static void __write_super(struct cache_sb *sb, struct cache_sb_disk *out,
 			offset_in_page(out));
 
 	out->offset		= cpu_to_le64(sb->offset);
-	out->version		= cpu_to_le64(sb->version);
 
 	memcpy(out->uuid,	sb->uuid, 16);
 	memcpy(out->set_uuid,	sb->set_uuid, 16);
@@ -257,6 +266,13 @@ static void __write_super(struct cache_sb *sb, struct cache_sb_disk *out,
 	for (i = 0; i < sb->keys; i++)
 		out->d[i] = cpu_to_le64(sb->d[i]);
 
+	if (sb->version >= BCACHE_SB_VERSION_CDEV_WITH_FEATURES) {
+		out->feature_compat    = cpu_to_le64(sb->feature_compat);
+		out->feature_incompat  = cpu_to_le64(sb->feature_incompat);
+		out->feature_ro_compat = cpu_to_le64(sb->feature_ro_compat);
+	}
+
+	out->version		= cpu_to_le64(sb->version);
 	out->csum = csum_set(out);
 
 	pr_debug("ver %llu, flags %llu, seq %llu\n",
@@ -313,17 +329,20 @@ void bcache_write_super(struct cache_set *c)
 {
 	struct closure *cl = &c->sb_write;
 	struct cache *ca;
-	unsigned int i;
+	unsigned int i, version = BCACHE_SB_VERSION_CDEV_WITH_UUID;
 
 	down(&c->sb_write_mutex);
 	closure_init(cl, &c->cl);
 
 	c->sb.seq++;
 
+	if (c->sb.version > version)
+		version = c->sb.version;
+
 	for_each_cache(ca, c, i) {
 		struct bio *bio = &ca->sb_bio;
 
-		ca->sb.version		= BCACHE_SB_VERSION_CDEV_WITH_UUID;
+		ca->sb.version		= version;
 		ca->sb.seq		= c->sb.seq;
 		ca->sb.last_mount	= c->sb.last_mount;
 
@@ -1839,6 +1858,13 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
 	c->sb.bucket_size	= sb->bucket_size;
 	c->sb.nr_in_set		= sb->nr_in_set;
 	c->sb.last_mount	= sb->last_mount;
+	c->sb.version		= sb->version;
+	if (c->sb.version >= BCACHE_SB_VERSION_CDEV_WITH_FEATURES) {
+		c->sb.feature_compat = sb->feature_compat;
+		c->sb.feature_ro_compat = sb->feature_ro_compat;
+		c->sb.feature_incompat = sb->feature_incompat;
+	}
+
 	c->bucket_bits		= ilog2(sb->bucket_size);
 	c->block_bits		= ilog2(sb->block_size);
 	c->nr_uuids		= bucket_bytes(c) / sizeof(struct uuid_entry);