Date:	Tue, 15 Sep 2015 01:09:00 -0400
From:	Dan Streetman <ddstreet@...e.org>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	Vitaly Wool <vitalywool@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 2/3] zpool/zsmalloc/zbud: align on interfaces

On Mon, Sep 14, 2015 at 9:06 PM, Sergey Senozhatsky
<sergey.senozhatsky.work@...il.com> wrote:
> On (09/14/15 15:51), Vitaly Wool wrote:
>> As a preparation step for zram to be able to use common zpool API,
>> there has to be some alignment done on it. This patch adds
>> functions that correspond to zsmalloc-specific API to the common
>> zpool API and takes care of the callbacks that have to be
>> introduced, too.
>>
>> Signed-off-by: Vitaly Wool <vitalywool@...il.com>
>> ---
>>  drivers/block/zram/zram_drv.c |  4 ++--
>>  include/linux/zpool.h         | 14 ++++++++++++++
>>  include/linux/zsmalloc.h      |  8 ++------
>>  mm/zbud.c                     | 12 ++++++++++++
>>  mm/zpool.c                    | 22 ++++++++++++++++++++++
>>  mm/zsmalloc.c                 | 23 ++++++++++++++++++++---
>>  6 files changed, 72 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
>> index 6d9f1d1..49d5a65 100644
>> --- a/drivers/block/zram/zram_drv.c
>> +++ b/drivers/block/zram/zram_drv.c
>> @@ -427,12 +427,12 @@ static ssize_t mm_stat_show(struct device *dev,
>>               struct device_attribute *attr, char *buf)
>>  {
>>       struct zram *zram = dev_to_zram(dev);
>> -     struct zs_pool_stats pool_stats;
>> +     struct zpool_stats pool_stats;
>>       u64 orig_size, mem_used = 0;
>>       long max_used;
>>       ssize_t ret;
>>
>> -     memset(&pool_stats, 0x00, sizeof(struct zs_pool_stats));
>> +     memset(&pool_stats, 0x00, sizeof(struct zpool_stats));
>>
>>       down_read(&zram->init_lock);
>>       if (init_done(zram)) {
>> diff --git a/include/linux/zpool.h b/include/linux/zpool.h
>> index 42f8ec9..f64cf86 100644
>> --- a/include/linux/zpool.h
>> +++ b/include/linux/zpool.h
>> @@ -17,6 +17,11 @@ struct zpool_ops {
>>       int (*evict)(struct zpool *pool, unsigned long handle);
>>  };
>>
>> +struct zpool_stats {
>> +     /* How many pages were migrated (freed) */
>> +     unsigned long pages_compacted;
>> +};
>> +
>>  /*
>>   * Control how a handle is mapped.  It will be ignored if the
>>   * implementation does not support it.  Its use is optional.
>> @@ -58,6 +63,10 @@ void *zpool_map_handle(struct zpool *pool, unsigned long handle,
>>
>>  void zpool_unmap_handle(struct zpool *pool, unsigned long handle);
>>
>> +int zpool_compact(struct zpool *pool, unsigned long *compacted);
>
> I see no reason for having this `unsigned long *compacted` param.
>
>
>> +void zpool_stats(struct zpool *pool, struct zpool_stats *zstats);
>> +
>>  u64 zpool_get_total_size(struct zpool *pool);
>>
>>
>> @@ -72,6 +81,8 @@ u64 zpool_get_total_size(struct zpool *pool);
>>   * @shrink:  shrink the pool.
>>   * @map:     map a handle.
>>   * @unmap:   unmap a handle.
>> + * @compact: try to run compaction for the pool
>> + * @stats:   get statistics for the pool
>>   * @total_size:      get total size of a pool.
>>   *
>>   * This is created by a zpool implementation and registered
>> @@ -98,6 +109,9 @@ struct zpool_driver {
>>                               enum zpool_mapmode mm);
>>       void (*unmap)(void *pool, unsigned long handle);
>>
>> +     int (*compact)(void *pool, unsigned long *compacted);
>> +     void (*stats)(void *pool, struct zpool_stats *stats);
>> +
>>       u64 (*total_size)(void *pool);
>>  };
>>
>> diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h
>> index 6398dfa..5aee1c7 100644
>> --- a/include/linux/zsmalloc.h
>> +++ b/include/linux/zsmalloc.h
>> @@ -15,6 +15,7 @@
>>  #define _ZS_MALLOC_H_
>>
>>  #include <linux/types.h>
>> +#include <linux/zpool.h>
>>
>>  /*
>>   * zsmalloc mapping modes
>> @@ -34,11 +35,6 @@ enum zs_mapmode {
>>        */
>>  };
>>
>> -struct zs_pool_stats {
>> -     /* How many pages were migrated (freed) */
>> -     unsigned long pages_compacted;
>> -};
>> -
>>  struct zs_pool;
>>
>>  struct zs_pool *zs_create_pool(char *name, gfp_t flags);
>> @@ -54,5 +50,5 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle);
>>  unsigned long zs_get_total_pages(struct zs_pool *pool);
>>  unsigned long zs_compact(struct zs_pool *pool);
>>
>> -void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats);
>> +void zs_pool_stats(struct zs_pool *pool, struct zpool_stats *stats);
>>  #endif
>> diff --git a/mm/zbud.c b/mm/zbud.c
>> index fa48bcdf..0963342 100644
>> --- a/mm/zbud.c
>> +++ b/mm/zbud.c
>> @@ -195,6 +195,16 @@ static void zbud_zpool_unmap(void *pool, unsigned long handle)
>>       zbud_unmap(pool, handle);
>>  }
>>
>> +static int zbud_zpool_compact(void *pool, unsigned long *compacted)
>> +{
>> +     return -EINVAL;
>> +}
>> +
>> +static void zbud_zpool_stats(void *pool, struct zpool_stats *stats)
>> +{
>> +     /* no-op */
>> +}
>> +
>>  static u64 zbud_zpool_total_size(void *pool)
>>  {
>>       return zbud_get_pool_size(pool) * PAGE_SIZE;
>> @@ -210,6 +220,8 @@ static struct zpool_driver zbud_zpool_driver = {
>>       .shrink =       zbud_zpool_shrink,
>>       .map =          zbud_zpool_map,
>>       .unmap =        zbud_zpool_unmap,
>> +     .compact =      zbud_zpool_compact,
>> +     .stats =        zbud_zpool_stats,
>>       .total_size =   zbud_zpool_total_size,
>>  };
>>
>> diff --git a/mm/zpool.c b/mm/zpool.c
>> index 8f670d3..15a171a 100644
>> --- a/mm/zpool.c
>> +++ b/mm/zpool.c
>> @@ -341,6 +341,28 @@ void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
>>  }
>>
>>  /**
>> + * zpool_compact() - try to run compaction over zpool
>> + * @pool     The zpool to compact
>> + * @compacted        The number of migrated pages
>> + *
>> + * Returns: 0 on success, error code otherwise
>> + */
>> +int zpool_compact(struct zpool *zpool, unsigned long *compacted)
>> +{
>> +     return zpool->driver->compact(zpool->pool, compacted);
>> +}
>> +
>> +/**
>> + * zpool_stats() - obtain zpool statistics
>> + * @pool     The zpool to get statistics for
>> + * @zstats   stats to fill in
>> + */
>> +void zpool_stats(struct zpool *zpool, struct zpool_stats *zstats)
>> +{
>> +     zpool->driver->stats(zpool->pool, zstats);
>> +}
>> +
>> +/**
>>   * zpool_get_total_size() - The total size of the pool
>>   * @pool     The zpool to check
>>   *
>> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
>> index f135b1b..f002f57 100644
>> --- a/mm/zsmalloc.c
>> +++ b/mm/zsmalloc.c
>> @@ -245,7 +245,7 @@ struct zs_pool {
>>       gfp_t flags;    /* allocation flags used when growing pool */
>>       atomic_long_t pages_allocated;
>>
>> -     struct zs_pool_stats stats;
>> +     struct zpool_stats stats;
>>
>>       /* Compact classes */
>>       struct shrinker shrinker;
>> @@ -365,6 +365,21 @@ static void zs_zpool_unmap(void *pool, unsigned long handle)
>>       zs_unmap_object(pool, handle);
>>  }
>>
>> +static int zs_zpool_compact(void *pool, unsigned long *compacted)
>> +{
>> +     unsigned long c = zs_compact(pool);
>> +
>> +     if (compacted)
>> +             *compacted = c;
>
> why not "return zs_compact(pool)"?

I agree it should just return zs_compact, and zbud can just always
return 0.  Any failures in compaction are going to be entirely
internal (besides an invalid pool, but there's bigger problems if that
happens), and there's nothing the caller can do with an error return
code.

Other than that, the patch looks fine to me, you can add (with that change)

Acked-by: Dan Streetman <ddstreet@...e.org>

>
>
>> +     return 0;
>> +}
>> +
>> +
>> +static void zs_zpool_stats(void *pool, struct zpool_stats *stats)
>> +{
>> +     zs_pool_stats(pool, stats);
>> +}
>> +
>>  static u64 zs_zpool_total_size(void *pool)
>>  {
>>       return zs_get_total_pages(pool) << PAGE_SHIFT;
>> @@ -380,6 +395,8 @@ static struct zpool_driver zs_zpool_driver = {
>>       .shrink =       zs_zpool_shrink,
>>       .map =          zs_zpool_map,
>>       .unmap =        zs_zpool_unmap,
>> +     .compact =      zs_zpool_compact,
>> +     .stats =        zs_zpool_stats,
>>       .total_size =   zs_zpool_total_size,
>>  };
>>
>> @@ -1789,9 +1806,9 @@ unsigned long zs_compact(struct zs_pool *pool)
>>  }
>>  EXPORT_SYMBOL_GPL(zs_compact);
>>
>> -void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats)
>> +void zs_pool_stats(struct zs_pool *pool, struct zpool_stats *stats)
>>  {
>> -     memcpy(stats, &pool->stats, sizeof(struct zs_pool_stats));
>> +     memcpy(stats, &pool->stats, sizeof(struct zpool_stats));
>>  }
>>  EXPORT_SYMBOL_GPL(zs_pool_stats);
>>
>> --
>> 1.9.1
>>
>> --
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