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bcache: increase super block version for cache device and backing device
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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 <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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Coly Li authored and axboe committed Jul 25, 2020
1 parent 117f636 commit d721a43
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Showing 3 changed files with 128 additions and 11 deletions.
78 changes: 78 additions & 0 deletions drivers/md/bcache/features.h
View file
Original file line number Diff line number Diff line change
@@ -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
32 changes: 29 additions & 3 deletions drivers/md/bcache/super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
#include "extents.h"
#include "request.h"
#include "writeback.h"
#include "features.h"

#include <linux/blkdev.h>
#include <linux/debugfs.h>
Expand Down Expand Up @@ -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";
Expand All @@ -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;
Expand Down Expand Up @@ -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);
Expand All @@ -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",
Expand Down Expand Up @@ -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;

Expand Down Expand Up @@ -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);
Expand Down
29 changes: 21 additions & 8 deletions include/uapi/linux/bcache.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -141,11 +141,13 @@ static inline struct bkey *bkey_idx(const struct bkey *k, unsigned int nr_keys)
* Version 3: Cache device with new UUID format
* Version 4: Backing device with data offset
*/
#define BCACHE_SB_VERSION_CDEV 0
#define BCACHE_SB_VERSION_BDEV 1
#define BCACHE_SB_VERSION_CDEV_WITH_UUID 3
#define BCACHE_SB_VERSION_BDEV_WITH_OFFSET 4
#define BCACHE_SB_MAX_VERSION 4
#define BCACHE_SB_VERSION_CDEV 0
#define BCACHE_SB_VERSION_BDEV 1
#define BCACHE_SB_VERSION_CDEV_WITH_UUID 3
#define BCACHE_SB_VERSION_BDEV_WITH_OFFSET 4
#define BCACHE_SB_VERSION_CDEV_WITH_FEATURES 5
#define BCACHE_SB_VERSION_BDEV_WITH_FEATURES 6
#define BCACHE_SB_MAX_VERSION 6

#define SB_SECTOR 8
#define SB_OFFSET (SB_SECTOR << SECTOR_SHIFT)
Expand Down Expand Up @@ -173,7 +175,12 @@ struct cache_sb_disk {

__le64 flags;
__le64 seq;
__le64 pad[8];

__le64 feature_compat;
__le64 feature_incompat;
__le64 feature_ro_compat;

__le64 pad[5];

union {
struct {
Expand Down Expand Up @@ -224,7 +231,12 @@ struct cache_sb {

__u64 flags;
__u64 seq;
__u64 pad[8];

__u64 feature_compat;
__u64 feature_incompat;
__u64 feature_ro_compat;

__u64 pad[5];

union {
struct {
Expand Down Expand Up @@ -262,7 +274,8 @@ struct cache_sb {
static inline _Bool SB_IS_BDEV(const struct cache_sb *sb)
{
return sb->version == BCACHE_SB_VERSION_BDEV
|| sb->version == BCACHE_SB_VERSION_BDEV_WITH_OFFSET;
|| sb->version == BCACHE_SB_VERSION_BDEV_WITH_OFFSET
|| sb->version == BCACHE_SB_VERSION_BDEV_WITH_FEATURES;
}

BITMASK(CACHE_SYNC, struct cache_sb, flags, 0, 1);
Expand Down

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