Re: [PATCH v2 1/1] mm: zswap - Add crypto acomp/scomp framework support

[Dan Streetman <ddstreet@ieee.org>]

On Fri, Feb 24, 2017 at 11:05 AM, Mahipal Challa
<Mahipal.Challa@cavium.com> wrote:
> This adds support for kernel's new crypto acomp/scomp framework
> to zswap.

I don't understand the point of this, zswap can't compress pages
asynchronously, so what benefit do we get from using the async crypto
api and then immediately waiting for it to finish?  This seems like
it's just adding complexity for no reason?

>
> Signed-off-by: Mahipal Challa <Mahipal.Challa@cavium.com>
> Signed-off-by: Vishnu Nair <Vishnu.Nair@cavium.com>
> ---
>  mm/zswap.c | 192 +++++++++++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 162 insertions(+), 30 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index cabf09e..b29d109 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -33,8 +33,10 @@
>  #include <linux/rbtree.h>
>  #include <linux/swap.h>
>  #include <linux/crypto.h>
> +#include <linux/scatterlist.h>
>  #include <linux/mempool.h>
>  #include <linux/zpool.h>
> +#include <crypto/acompress.h>
>
>  #include <linux/mm_types.h>
>  #include <linux/page-flags.h>
> @@ -118,9 +120,21 @@ static int zswap_compressor_param_set(const char *,
>  * data structures
>  **********************************/
>
> +/**
> + * struct zswap_acomp_result - Data structure to store result of acomp callback
> + * @completion: zswap will wait for completion on this entry
> + * @err       : return value from acomp algorithm will be stored here
> + */
> +struct zswap_acomp_result {
> +       struct completion completion;
> +       int err;
> +};
> +
>  struct zswap_pool {
>         struct zpool *zpool;
> -       struct crypto_comp * __percpu *tfm;
> +       struct crypto_acomp * __percpu *acomp;
> +       struct acomp_req * __percpu *acomp_req;
> +       struct zswap_acomp_result * __percpu *result;
>         struct kref kref;
>         struct list_head list;
>         struct work_struct work;
> @@ -388,30 +402,66 @@ static int zswap_dstmem_dead(unsigned int cpu)
>  static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
>  {
>         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
> -       struct crypto_comp *tfm;
> +       struct crypto_acomp *acomp;
> +       struct acomp_req *acomp_req;
> +       struct zswap_acomp_result *result;
>
> -       if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
> +       if (WARN_ON(*per_cpu_ptr(pool->acomp, cpu)))
>                 return 0;
> +       if (WARN_ON(*per_cpu_ptr(pool->acomp_req, cpu)))
> +               return 0;
> +       if (WARN_ON(*per_cpu_ptr(pool->result, cpu)))
> +               return 0;
> +
> +       acomp = crypto_alloc_acomp(pool->tfm_name, 0, 0);
> +       if (IS_ERR_OR_NULL(acomp)) {
> +               pr_err("could not alloc crypto acomp %s : %ld\n",
> +                      pool->tfm_name, PTR_ERR(acomp));
> +               return -ENOMEM;
> +       }
> +       *per_cpu_ptr(pool->acomp, cpu) = acomp;
> +
> +       acomp_req = acomp_request_alloc(acomp);
> +       if (IS_ERR_OR_NULL(acomp_req)) {
> +               pr_err("could not alloc crypto acomp %s : %ld\n",
> +                      pool->tfm_name, PTR_ERR(acomp));
> +               return -ENOMEM;
> +       }
> +       *per_cpu_ptr(pool->acomp_req, cpu) = acomp_req;
>
> -       tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
> -       if (IS_ERR_OR_NULL(tfm)) {
> -               pr_err("could not alloc crypto comp %s : %ld\n",
> -                      pool->tfm_name, PTR_ERR(tfm));
> +       result = kzalloc(sizeof(*result), GFP_KERNEL);
> +       if (IS_ERR_OR_NULL(result)) {
> +               pr_err("Could not initialize completion on result\n");
>                 return -ENOMEM;
>         }
> -       *per_cpu_ptr(pool->tfm, cpu) = tfm;
> +       init_completion(&result->completion);
> +       *per_cpu_ptr(pool->result, cpu) = result;
> +
>         return 0;
>  }
>
>  static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
>  {
>         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
> -       struct crypto_comp *tfm;
> +       struct crypto_acomp *acomp;
> +       struct acomp_req *acomp_req;
> +       struct zswap_acomp_result *result;
> +
> +       acomp_req = *per_cpu_ptr(pool->acomp_req, cpu);
> +       if (!IS_ERR_OR_NULL(acomp_req))
> +               acomp_request_free(acomp_req);
> +       *per_cpu_ptr(pool->acomp_req, cpu) = NULL;
> +
> +       acomp = *per_cpu_ptr(pool->acomp, cpu);
> +       if (!IS_ERR_OR_NULL(acomp))
> +               crypto_free_acomp(acomp);
> +       *per_cpu_ptr(pool->acomp, cpu) = NULL;
> +
> +       result = *per_cpu_ptr(pool->result, cpu);
> +       if (!IS_ERR_OR_NULL(result))
> +               kfree(result);
> +       *per_cpu_ptr(pool->result, cpu) = NULL;
>
> -       tfm = *per_cpu_ptr(pool->tfm, cpu);
> -       if (!IS_ERR_OR_NULL(tfm))
> -               crypto_free_comp(tfm);
> -       *per_cpu_ptr(pool->tfm, cpu) = NULL;
>         return 0;
>  }
>
> @@ -512,8 +562,20 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
>         pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
>
>         strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
> -       pool->tfm = alloc_percpu(struct crypto_comp *);
> -       if (!pool->tfm) {
> +       pool->acomp = alloc_percpu(struct crypto_acomp *);
> +       if (!pool->acomp) {
> +               pr_err("percpu alloc failed\n");
> +               goto error;
> +       }
> +
> +       pool->acomp_req = alloc_percpu(struct acomp_req *);
> +       if (!pool->acomp_req) {
> +               pr_err("percpu alloc failed\n");
> +               goto error;
> +       }
> +
> +       pool->result = alloc_percpu(struct zswap_acomp_result *);
> +       if (!pool->result) {
>                 pr_err("percpu alloc failed\n");
>                 goto error;
>         }
> @@ -535,7 +597,9 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
>         return pool;
>
>  error:
> -       free_percpu(pool->tfm);
> +       free_percpu(pool->result);
> +       free_percpu(pool->acomp_req);
> +       free_percpu(pool->acomp);
>         if (pool->zpool)
>                 zpool_destroy_pool(pool->zpool);
>         kfree(pool);
> @@ -575,7 +639,9 @@ static void zswap_pool_destroy(struct zswap_pool *pool)
>         zswap_pool_debug("destroying", pool);
>
>         cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
> -       free_percpu(pool->tfm);
> +       free_percpu(pool->result);
> +       free_percpu(pool->acomp_req);
> +       free_percpu(pool->acomp);
>         zpool_destroy_pool(pool->zpool);
>         kfree(pool);
>  }
> @@ -622,6 +688,30 @@ static void zswap_pool_put(struct zswap_pool *pool)
>  }
>
>  /*********************************
> +* CRYPTO_ACOMPRESS wait and callbacks
> +**********************************/
> +static void zswap_acomp_callback(struct crypto_async_request *req, int err)
> +{
> +       struct zswap_acomp_result *res = req->data;
> +
> +       if (err == -EINPROGRESS)
> +               return;
> +
> +       res->err = err;
> +       complete(&res->completion);
> +}
> +
> +static int zswap_wait_acomp(struct zswap_acomp_result *res, int ret)
> +{
> +       if (ret == -EINPROGRESS || ret == -EBUSY) {
> +               wait_for_completion(&res->completion);
> +               reinit_completion(&res->completion);
> +               ret = res->err;
> +       }
> +       return ret;
> +}
> +
> +/*********************************
>  * param callbacks
>  **********************************/
>
> @@ -788,7 +878,9 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
>         pgoff_t offset;
>         struct zswap_entry *entry;
>         struct page *page;
> -       struct crypto_comp *tfm;
> +       struct scatterlist input, output;
> +       struct acomp_req *req;
> +       struct zswap_acomp_result *result;
>         u8 *src, *dst;
>         unsigned int dlen;
>         int ret;
> @@ -828,14 +920,25 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
>
>         case ZSWAP_SWAPCACHE_NEW: /* page is locked */
>                 /* decompress */
> +               req = *get_cpu_ptr(entry->pool->acomp_req);
>                 dlen = PAGE_SIZE;
>                 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
>                                 ZPOOL_MM_RO) + sizeof(struct zswap_header);
>                 dst = kmap_atomic(page);
> -               tfm = *get_cpu_ptr(entry->pool->tfm);
> -               ret = crypto_comp_decompress(tfm, src, entry->length,
> -                                            dst, &dlen);
> -               put_cpu_ptr(entry->pool->tfm);
> +
> +               result = *get_cpu_ptr(entry->pool->result);
> +               sg_init_one(&input, src, entry->length);
> +               sg_init_one(&output, dst, dlen);
> +               acomp_request_set_params(req, &input, &output, entry->length,
> +                                        dlen);
> +               acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
> +                                          zswap_acomp_callback, result);
> +
> +               ret = zswap_wait_acomp(result, crypto_acomp_decompress(req));
> +
> +               dlen = req->dlen;
> +               put_cpu_ptr(entry->pool->acomp_req);
> +               put_cpu_ptr(entry->pool->result);
>                 kunmap_atomic(dst);
>                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
>                 BUG_ON(ret);
> @@ -911,7 +1014,9 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
>  {
>         struct zswap_tree *tree = zswap_trees[type];
>         struct zswap_entry *entry, *dupentry;
> -       struct crypto_comp *tfm;
> +       struct scatterlist input, output;
> +       struct acomp_req *req;
> +       struct zswap_acomp_result *result;
>         int ret;
>         unsigned int dlen = PAGE_SIZE, len;
>         unsigned long handle;
> @@ -950,12 +1055,24 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
>         }
>
>         /* compress */
> +       req = *get_cpu_ptr(entry->pool->acomp_req);
> +       result = *get_cpu_ptr(entry->pool->result);
> +
>         dst = get_cpu_var(zswap_dstmem);
> -       tfm = *get_cpu_ptr(entry->pool->tfm);
>         src = kmap_atomic(page);
> -       ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
> +
> +       sg_init_one(&input, src, PAGE_SIZE);
> +       /* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
> +       sg_init_one(&output, dst, PAGE_SIZE * 2);
> +       acomp_request_set_params(req, &input, &output, PAGE_SIZE, dlen);
> +       acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
> +                                  zswap_acomp_callback, result);
> +
> +       ret = zswap_wait_acomp(result, crypto_acomp_compress(req));
>         kunmap_atomic(src);
> -       put_cpu_ptr(entry->pool->tfm);
> +       put_cpu_ptr(entry->pool->acomp_req);
> +       put_cpu_ptr(entry->pool->result);
> +       dlen = req->dlen;
>         if (ret) {
>                 ret = -EINVAL;
>                 goto put_dstmem;
> @@ -1023,7 +1140,9 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
>  {
>         struct zswap_tree *tree = zswap_trees[type];
>         struct zswap_entry *entry;
> -       struct crypto_comp *tfm;
> +       struct scatterlist input, output;
> +       struct acomp_req *req;
> +       struct zswap_acomp_result *result;
>         u8 *src, *dst;
>         unsigned int dlen;
>         int ret;
> @@ -1039,13 +1158,25 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
>         spin_unlock(&tree->lock);
>
>         /* decompress */
> +       req = *get_cpu_ptr(entry->pool->acomp_req);
> +       result = *get_cpu_ptr(entry->pool->result);
> +
>         dlen = PAGE_SIZE;
>         src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
>                         ZPOOL_MM_RO) + sizeof(struct zswap_header);
>         dst = kmap_atomic(page);
> -       tfm = *get_cpu_ptr(entry->pool->tfm);
> -       ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
> -       put_cpu_ptr(entry->pool->tfm);
> +
> +       sg_init_one(&input, src, entry->length);
> +       sg_init_one(&output, dst, dlen);
> +       acomp_request_set_params(req, &input, &output, entry->length, dlen);
> +       acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
> +                                  zswap_acomp_callback, result);
> +
> +       ret = zswap_wait_acomp(result, crypto_acomp_decompress(req));
> +
> +       dlen = req->dlen;
> +       put_cpu_ptr(entry->pool->acomp_req);
> +       put_cpu_ptr(entry->pool->result);
>         kunmap_atomic(dst);
>         zpool_unmap_handle(entry->pool->zpool, entry->handle);
>         BUG_ON(ret);
> @@ -1237,3 +1368,4 @@ static int __init init_zswap(void)
>  MODULE_LICENSE("GPL");
>  MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
>  MODULE_DESCRIPTION("Compressed cache for swap pages");
> +
> --
> 1.8.3.1
>

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