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List:       linux-bcache
Subject:    Re: [PATCH v2 02/12] bcache: explicitly make cache_set only have single cache
From:       Coly Li <colyli () suse ! de>
Date:       2020-08-25 11:08:01
Message-ID: 4e8c76d7-04c4-f33c-ea0b-74dfceb9ae01 () suse ! de
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On 2020/8/25 14:17, Hannes Reinecke wrote:
> On 8/22/20 1:45 PM, Coly Li wrote:
>> Currently although the bcache code has a framework for multiple caches
>> in a cache set, but indeed the multiple caches never completed and users
>> use md raid1 for multiple copies of the cached data.
>>
>> This patch does the following change in struct cache_set, to explicitly
>> make a cache_set only have single cache,
>> - Change pointer array "*cache[MAX_CACHES_PER_SET]" to a single pointer
>>    "*cache".
>> - Remove pointer array "*cache_by_alloc[MAX_CACHES_PER_SET]".
>> - Remove "caches_loaded".
>>
>> Now the code looks as exactly what it does in practic: only one cache is
>> used in the cache set.
>>
>> Signed-off-by: Coly Li <colyli@suse.de>
>> ---
>>   drivers/md/bcache/alloc.c  |  2 +-
>>   drivers/md/bcache/bcache.h |  8 +++-----
>>   drivers/md/bcache/super.c  | 19 ++++++++-----------
>>   3 files changed, 12 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
>> index 4493ff57476d..3385f6add6df 100644
>> --- a/drivers/md/bcache/alloc.c
>> +++ b/drivers/md/bcache/alloc.c
>> @@ -501,7 +501,7 @@ int __bch_bucket_alloc_set(struct cache_set *c,
>> unsigned int reserve,
>>         bkey_init(k);
>>   -    ca = c->cache_by_alloc[0];
>> +    ca = c->cache;
>>       b = bch_bucket_alloc(ca, reserve, wait);
>>       if (b == -1)
>>           goto err;
>> diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
>> index 5ff6e9573935..aa112c1adba1 100644
>> --- a/drivers/md/bcache/bcache.h
>> +++ b/drivers/md/bcache/bcache.h
>> @@ -519,9 +519,7 @@ struct cache_set {
>>         struct cache_sb        sb;
>>   -    struct cache        *cache[MAX_CACHES_PER_SET];
>> -    struct cache        *cache_by_alloc[MAX_CACHES_PER_SET];
>> -    int            caches_loaded;
>> +    struct cache        *cache;
>>         struct bcache_device    **devices;
>>       unsigned int        devices_max_used;
>> @@ -808,7 +806,7 @@ static inline struct cache *PTR_CACHE(struct
>> cache_set *c,
>>                         const struct bkey *k,
>>                         unsigned int ptr)
>>   {
>> -    return c->cache[PTR_DEV(k, ptr)];
>> +    return c->cache;
>>   }
>>     static inline size_t PTR_BUCKET_NR(struct cache_set *c,
>> @@ -890,7 +888,7 @@ do {                                    \
>>   /* Looping macros */
>>     #define for_each_cache(ca, cs, iter)                    \
>> -    for (iter = 0; ca = cs->cache[iter], iter < (cs)->sb.nr_in_set;
>> iter++)
>> +    for (iter = 0; ca = cs->cache, iter < 1; iter++)
>>     #define for_each_bucket(b, ca)                        \
>>       for (b = (ca)->buckets + (ca)->sb.first_bucket;            \
>> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
>> index 7057ec48f3d1..e9ccfa17beb8 100644
>> --- a/drivers/md/bcache/super.c
>> +++ b/drivers/md/bcache/super.c
>> @@ -1675,7 +1675,7 @@ static void cache_set_free(struct closure *cl)
>>       for_each_cache(ca, c, i)
>>           if (ca) {
>>               ca->set = NULL;
>> -            c->cache[ca->sb.nr_this_dev] = NULL;
>> +            c->cache = NULL;
>>               kobject_put(&ca->kobj);
>>           }
>>   
> Please kill 'for_each_cache()', too, and replace it by an if clause.

Yes, it is done in next patch: [PATCH v2 03/12] bcache: remove
for_each_cache()

Thanks.

Coly Li
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