Re: [PATCH] bcache: make checkings for sb.nr_in_set and sb.nr_this_dev to be more precise

From: Coly Li
Date: Mon Nov 01 2021 - 01:29:19 EST


On 11/1/21 11:07 AM, Lin Feng wrote:
Commit 697e23495c94f0380c1ed8b11f830b92b64c99ea
("bcache: explicitly make cache_set only have single cache")
explicitly makes a cache_set only have single cache and based on the
fact that historily only one cache is ever used in the cache set, so
valid number fo sb.nr_in_set should be 1 and sb.nr_this_dev should
always be 0.

Based on above truth, codes validations for sb.nr_in_set and sb.nr_this_dev
can make to be more accurate, that means tolerance for error checking
are reduced comparing before.

Signed-off-by: Lin Feng <linf@xxxxxxxxxx>

Hi Lin,

Thanks for the patch up. I add this change to my for-test directory.

Coly Li


---
drivers/md/bcache/bcache.h | 2 +-
drivers/md/bcache/super.c | 4 +---
2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 5fc989a6d452..a4a410a178c0 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -833,7 +833,7 @@ static inline uint8_t ptr_stale(struct cache_set *c, const struct bkey *k,
static inline bool ptr_available(struct cache_set *c, const struct bkey *k,
unsigned int i)
{
- return (PTR_DEV(k, i) < MAX_CACHES_PER_SET) && c->cache;
+ return (PTR_DEV(k, i) == 0) && c->cache;
}
/* Btree key macros */
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index f2874c77ff79..2253044c9289 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -140,9 +140,7 @@ static const char *read_super_common(struct cache_sb *sb, struct block_device *
goto err;
err = "Bad cache device number in set";
- if (!sb->nr_in_set ||
- sb->nr_in_set <= sb->nr_this_dev ||
- sb->nr_in_set > MAX_CACHES_PER_SET)
+ if (sb->nr_in_set != 1 || sb->nr_this_dev != 0)
goto err;
err = "Journal buckets not sequential";