[PATCH v1 09/14] bcache: avoid data copy between cache_set->sb and cache->sb

colyli
2020-08-15T22:24:04Z

struct cache_sb embedded in struct cache_set is only partial used and
not a real copy from cache's in-memory super block. When removing the
embedded cache_set->sb, it is unncessary to copy data between these two
in-memory super blocks (cache_set->sb and cache->sb), it is sufficient
to just use cache->sb.

This patch removes the data copy between these two in-memory super
blocks in bch_cache_set_alloc() and bcache_write_super(). In future
except for set_uuid, cache's super block will be referenced by cache
set, no copy any more.

Signed-off-by: Coly Li <colyli@suse.de>
---
drivers/md/bcache/super.c | 22 +++-------------------
1 file changed, 3 insertions(+), 19 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 28257f11d835..20de004ab2ef 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -350,16 +350,10 @@ void bcache_write_super(struct cache_set *c)
down(&c->sb_write_mutex);
closure_init(cl, &c->cl);

- c->sb.seq++;
+ ca->sb.seq++;

- if (c->sb.version > version)
- version = c->sb.version;
-
- ca->sb.version = version;
- ca->sb.seq = c->sb.seq;
- ca->sb.last_mount = c->sb.last_mount;
-
- SET_CACHE_SYNC(&ca->sb, CACHE_SYNC(&c->sb));
+ if (ca->sb.version < version)
+ ca->sb.version = version;

bio_init(bio, ca->sb_bv, 1);
bio_set_dev(bio, ca->bdev);
@@ -1860,16 +1854,6 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
bch_cache_accounting_init(&c->accounting, &c->cl);

memcpy(c->set_uuid, sb->set_uuid, 16);
- c->sb.block_size = sb->block_size;
- 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);
--
2.26.2