Re: [PATCH] bcache: kill macro MAX_CACHES_PER_SET

[Lin Feng]

Hi Coly,

OK, I will send another patch but keep MAX_CACHES_PER_SET, thanks :)

linfeng

On 10/30/21 23:19, Coly Li wrote:
> On 10/29/21 8:59 PM, 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
> > macro defination for MAX_CACHES_PER_SET as 8 is misleading now.
> >
> > In fact it should be redefined to 1 and valid number fo sb.nr_in_set
> > should be 1 and sb.nr_this_dev should always be 0.
> >
> > But jset's disk layout replies on MAX_CACHES_PER_SET(8), so replace it
> > with a hardcoded number 8.
> >
> > Signed-off-by: Lin Feng <linf@xxxxxxxxxx>
> > ---
> >    drivers/md/bcache/bcache.h  | 2 +-
> >    drivers/md/bcache/super.c   | 4 +---
> >    include/uapi/linux/bcache.h | 4 ++--
> >    3 files changed, 4 insertions(+), 6 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";
>
> Hi Feng,
>
> The above changes are fine to me. But let's keep the below part as what
> it is at this moment.
>
> Thanks.
>
> Coly Li
>
> > diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h
> > index cf7399f03b71..4beb3e7826ca 100644
> > --- a/include/uapi/linux/bcache.h
> > +++ b/include/uapi/linux/bcache.h
> > @@ -155,7 +155,6 @@ static inline struct bkey *bkey_idx(const struct bkey *k, unsigned int nr_keys)
> >    #define SB_LABEL_SIZE			32
> >    #define SB_JOURNAL_BUCKETS		256U
> >    /* SB_JOURNAL_BUCKETS must be divisible by BITS_PER_LONG */
> > -#define MAX_CACHES_PER_SET		8
> >    
> >    #define BDEV_DATA_START_DEFAULT		16	/* sectors */
> >    
> > @@ -356,7 +355,8 @@ struct jset {
> >    	__u16			btree_level;
> >    	__u16			pad[3];
> >    
> > -	__u64			prio_bucket[MAX_CACHES_PER_SET];
> > +	/* only a single cache is available */
> > +	__u64			prio_bucket[8];
> >    
> >    	union {
> >    		struct bkey	start[0];