Re: [PATCH 10/20] mm: zswap: function ordering: pool alloc & free

[Nhat Pham <nphamcs@gmail.com>]

On Mon, Jan 29, 2024 at 5:42 PM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> The function ordering in zswap.c is a little chaotic, which requires
> jumping in unexpected directions when following related code. This is
> a series of patches that brings the file into the following order:
>
> - pool functions
> - lru functions
> - rbtree functions
> - zswap entry functions
> - compression/backend functions
> - writeback & shrinking functions
> - store, load, invalidate, swapon, swapoff
> - debugfs
> - init

This ordering seems reasonable to me. Then again, we don't have any
coherent ordering of functions, so anything would be an improvement :)


>
> But it has to be split up such the moving still produces halfway
> readable diffs.
>
> In this patch, move pool allocation and freeing functions.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Nhat Pham <nphamcs@gmail.com>

> ---
>  mm/zswap.c | 297 +++++++++++++++++++++++++++--------------------------
>  1 file changed, 152 insertions(+), 145 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 082d076a758d..805d9a35f633 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -320,6 +320,158 @@ static void zswap_update_total_size(void)
>         zswap_pool_total_size = total;
>  }
>
> +/*********************************
> +* pool functions
> +**********************************/
> +
> +static void zswap_alloc_shrinker(struct zswap_pool *pool);
> +static void shrink_worker(struct work_struct *w);
> +
> +static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
> +{
> +       int i;
> +       struct zswap_pool *pool;
> +       char name[38]; /* 'zswap' + 32 char (max) num + \0 */
> +       gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
> +       int ret;
> +
> +       if (!zswap_has_pool) {
> +               /* if either are unset, pool initialization failed, and we
> +                * need both params to be set correctly before trying to
> +                * create a pool.
> +                */
> +               if (!strcmp(type, ZSWAP_PARAM_UNSET))
> +                       return NULL;
> +               if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
> +                       return NULL;
> +       }
> +
> +       pool = kzalloc(sizeof(*pool), GFP_KERNEL);
> +       if (!pool)
> +               return NULL;
> +
> +       for (i = 0; i < ZSWAP_NR_ZPOOLS; i++) {
> +               /* unique name for each pool specifically required by zsmalloc */
> +               snprintf(name, 38, "zswap%x",
> +                        atomic_inc_return(&zswap_pools_count));
> +
> +               pool->zpools[i] = zpool_create_pool(type, name, gfp);
> +               if (!pool->zpools[i]) {
> +                       pr_err("%s zpool not available\n", type);
> +                       goto error;
> +               }
> +       }
> +       pr_debug("using %s zpool\n", zpool_get_type(pool->zpools[0]));
> +
> +       strscpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
> +
> +       pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx);
> +       if (!pool->acomp_ctx) {
> +               pr_err("percpu alloc failed\n");
> +               goto error;
> +       }
> +
> +       ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
> +                                      &pool->node);
> +       if (ret)
> +               goto error;
> +
> +       zswap_alloc_shrinker(pool);
> +       if (!pool->shrinker)
> +               goto error;
> +
> +       pr_debug("using %s compressor\n", pool->tfm_name);
> +
> +       /* being the current pool takes 1 ref; this func expects the
> +        * caller to always add the new pool as the current pool
> +        */
> +       kref_init(&pool->kref);
> +       INIT_LIST_HEAD(&pool->list);
> +       if (list_lru_init_memcg(&pool->list_lru, pool->shrinker))
> +               goto lru_fail;
> +       shrinker_register(pool->shrinker);
> +       INIT_WORK(&pool->shrink_work, shrink_worker);
> +       atomic_set(&pool->nr_stored, 0);
> +
> +       zswap_pool_debug("created", pool);
> +
> +       return pool;
> +
> +lru_fail:
> +       list_lru_destroy(&pool->list_lru);
> +       shrinker_free(pool->shrinker);
> +error:
> +       if (pool->acomp_ctx)
> +               free_percpu(pool->acomp_ctx);
> +       while (i--)
> +               zpool_destroy_pool(pool->zpools[i]);
> +       kfree(pool);
> +       return NULL;
> +}
> +
> +static struct zswap_pool *__zswap_pool_create_fallback(void)
> +{
> +       bool has_comp, has_zpool;
> +
> +       has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
> +       if (!has_comp && strcmp(zswap_compressor,
> +                               CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
> +               pr_err("compressor %s not available, using default %s\n",
> +                      zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
> +               param_free_charp(&zswap_compressor);
> +               zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
> +               has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
> +       }
> +       if (!has_comp) {
> +               pr_err("default compressor %s not available\n",
> +                      zswap_compressor);
> +               param_free_charp(&zswap_compressor);
> +               zswap_compressor = ZSWAP_PARAM_UNSET;
> +       }
> +
> +       has_zpool = zpool_has_pool(zswap_zpool_type);
> +       if (!has_zpool && strcmp(zswap_zpool_type,
> +                                CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
> +               pr_err("zpool %s not available, using default %s\n",
> +                      zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
> +               param_free_charp(&zswap_zpool_type);
> +               zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
> +               has_zpool = zpool_has_pool(zswap_zpool_type);
> +       }
> +       if (!has_zpool) {
> +               pr_err("default zpool %s not available\n",
> +                      zswap_zpool_type);
> +               param_free_charp(&zswap_zpool_type);
> +               zswap_zpool_type = ZSWAP_PARAM_UNSET;
> +       }
> +
> +       if (!has_comp || !has_zpool)
> +               return NULL;
> +
> +       return zswap_pool_create(zswap_zpool_type, zswap_compressor);
> +}
> +
> +static void zswap_pool_destroy(struct zswap_pool *pool)
> +{
> +       int i;
> +
> +       zswap_pool_debug("destroying", pool);
> +
> +       shrinker_free(pool->shrinker);
> +       cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
> +       free_percpu(pool->acomp_ctx);
> +       list_lru_destroy(&pool->list_lru);
> +
> +       spin_lock(&zswap_pools_lock);
> +       mem_cgroup_iter_break(NULL, pool->next_shrink);
> +       pool->next_shrink = NULL;
> +       spin_unlock(&zswap_pools_lock);
> +
> +       for (i = 0; i < ZSWAP_NR_ZPOOLS; i++)
> +               zpool_destroy_pool(pool->zpools[i]);
> +       kfree(pool);
> +}
> +
>  /* should be called under RCU */
>  #ifdef CONFIG_MEMCG
>  static inline struct mem_cgroup *mem_cgroup_from_entry(struct zswap_entry *entry)
> @@ -970,151 +1122,6 @@ static void shrink_worker(struct work_struct *w)
>         zswap_pool_put(pool);
>  }
>
> -static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
> -{
> -       int i;
> -       struct zswap_pool *pool;
> -       char name[38]; /* 'zswap' + 32 char (max) num + \0 */
> -       gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
> -       int ret;
> -
> -       if (!zswap_has_pool) {
> -               /* if either are unset, pool initialization failed, and we
> -                * need both params to be set correctly before trying to
> -                * create a pool.
> -                */
> -               if (!strcmp(type, ZSWAP_PARAM_UNSET))
> -                       return NULL;
> -               if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
> -                       return NULL;
> -       }
> -
> -       pool = kzalloc(sizeof(*pool), GFP_KERNEL);
> -       if (!pool)
> -               return NULL;
> -
> -       for (i = 0; i < ZSWAP_NR_ZPOOLS; i++) {
> -               /* unique name for each pool specifically required by zsmalloc */
> -               snprintf(name, 38, "zswap%x",
> -                        atomic_inc_return(&zswap_pools_count));
> -
> -               pool->zpools[i] = zpool_create_pool(type, name, gfp);
> -               if (!pool->zpools[i]) {
> -                       pr_err("%s zpool not available\n", type);
> -                       goto error;
> -               }
> -       }
> -       pr_debug("using %s zpool\n", zpool_get_type(pool->zpools[0]));
> -
> -       strscpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
> -
> -       pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx);
> -       if (!pool->acomp_ctx) {
> -               pr_err("percpu alloc failed\n");
> -               goto error;
> -       }
> -
> -       ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
> -                                      &pool->node);
> -       if (ret)
> -               goto error;
> -
> -       zswap_alloc_shrinker(pool);
> -       if (!pool->shrinker)
> -               goto error;
> -
> -       pr_debug("using %s compressor\n", pool->tfm_name);
> -
> -       /* being the current pool takes 1 ref; this func expects the
> -        * caller to always add the new pool as the current pool
> -        */
> -       kref_init(&pool->kref);
> -       INIT_LIST_HEAD(&pool->list);
> -       if (list_lru_init_memcg(&pool->list_lru, pool->shrinker))
> -               goto lru_fail;
> -       shrinker_register(pool->shrinker);
> -       INIT_WORK(&pool->shrink_work, shrink_worker);
> -       atomic_set(&pool->nr_stored, 0);
> -
> -       zswap_pool_debug("created", pool);
> -
> -       return pool;
> -
> -lru_fail:
> -       list_lru_destroy(&pool->list_lru);
> -       shrinker_free(pool->shrinker);
> -error:
> -       if (pool->acomp_ctx)
> -               free_percpu(pool->acomp_ctx);
> -       while (i--)
> -               zpool_destroy_pool(pool->zpools[i]);
> -       kfree(pool);
> -       return NULL;
> -}
> -
> -static struct zswap_pool *__zswap_pool_create_fallback(void)
> -{
> -       bool has_comp, has_zpool;
> -
> -       has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
> -       if (!has_comp && strcmp(zswap_compressor,
> -                               CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
> -               pr_err("compressor %s not available, using default %s\n",
> -                      zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
> -               param_free_charp(&zswap_compressor);
> -               zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
> -               has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
> -       }
> -       if (!has_comp) {
> -               pr_err("default compressor %s not available\n",
> -                      zswap_compressor);
> -               param_free_charp(&zswap_compressor);
> -               zswap_compressor = ZSWAP_PARAM_UNSET;
> -       }
> -
> -       has_zpool = zpool_has_pool(zswap_zpool_type);
> -       if (!has_zpool && strcmp(zswap_zpool_type,
> -                                CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
> -               pr_err("zpool %s not available, using default %s\n",
> -                      zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
> -               param_free_charp(&zswap_zpool_type);
> -               zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
> -               has_zpool = zpool_has_pool(zswap_zpool_type);
> -       }
> -       if (!has_zpool) {
> -               pr_err("default zpool %s not available\n",
> -                      zswap_zpool_type);
> -               param_free_charp(&zswap_zpool_type);
> -               zswap_zpool_type = ZSWAP_PARAM_UNSET;
> -       }
> -
> -       if (!has_comp || !has_zpool)
> -               return NULL;
> -
> -       return zswap_pool_create(zswap_zpool_type, zswap_compressor);
> -}
> -
> -static void zswap_pool_destroy(struct zswap_pool *pool)
> -{
> -       int i;
> -
> -       zswap_pool_debug("destroying", pool);
> -
> -       shrinker_free(pool->shrinker);
> -       cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
> -       free_percpu(pool->acomp_ctx);
> -       list_lru_destroy(&pool->list_lru);
> -
> -       spin_lock(&zswap_pools_lock);
> -       mem_cgroup_iter_break(NULL, pool->next_shrink);
> -       pool->next_shrink = NULL;
> -       spin_unlock(&zswap_pools_lock);
> -
> -       for (i = 0; i < ZSWAP_NR_ZPOOLS; i++)
> -               zpool_destroy_pool(pool->zpools[i]);
> -       kfree(pool);
> -}
> -
>  static int __must_check zswap_pool_get(struct zswap_pool *pool)
>  {
>         if (!pool)
> --
> 2.43.0
>