Re: [RFC PATCH v1 1/1] mm: zswap - Add crypto acomp/scomp framework support

[Narayana Prasad Athreya <pathreya@caviumnetworks.com>]

> I assume all of these crypto_acomp_[compress|decompress] calls are
> actually synchronous,
> not asynchronous as the name suggests.  Otherwise, this would blow up
> quite spectacularly
> since all the resources we use in the call get derefed/unmapped below.
>
> Could an async algorithm be implement/used that would break this assumption?

The callback is set to NULL using acomp_request_set_callback(). This 
implies synchronous mode of operation. So the underlying implementation 
must complete the operation synchronously.

Prasad

On Tuesday 14 February 2017 09:50 PM, Seth Jennings wrote:
> On Tue, Feb 14, 2017 at 9:40 AM, Mahipal Challa
> <mahipalreddy2006@gmail.com> wrote:
>> This adds the support for kernel's crypto new acomp/scomp framework
>> to zswap.
>>
>> Signed-off-by: Mahipal Challa <Mahipal.Challa@cavium.com>
>> Signed-off-by: Vishnu Nair <Vishnu.Nair@cavium.com>
>> ---
>>   mm/zswap.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++--------------
>>   1 file changed, 99 insertions(+), 30 deletions(-)
>>
>> diff --git a/mm/zswap.c b/mm/zswap.c
>> index 067a0d6..d08631b 100644
>> --- a/mm/zswap.c
>> +++ b/mm/zswap.c
>> @@ -33,6 +33,8 @@
>>   #include <linux/rbtree.h>
>>   #include <linux/swap.h>
>>   #include <linux/crypto.h>
>> +#include <crypto/acompress.h>
>> +#include <linux/scatterlist.h>
>>   #include <linux/mempool.h>
>>   #include <linux/zpool.h>
>>
>> @@ -114,7 +116,8 @@ static int zswap_compressor_param_set(const char *,
>>
>>   struct zswap_pool {
>>          struct zpool *zpool;
>> -       struct crypto_comp * __percpu *tfm;
>> +       struct crypto_acomp * __percpu *acomp;
>> +       struct acomp_req * __percpu *acomp_req;
>>          struct kref kref;
>>          struct list_head list;
>>          struct work_struct work;
>> @@ -379,30 +382,49 @@ 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;
>>
>> -       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;
>> +
>> +       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;
>>
>> -       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));
>> +       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->tfm, cpu) = tfm;
>> +       *per_cpu_ptr(pool->acomp_req, cpu) = acomp_req;
>> +
>>          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;
>> +
>> +       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;
>>
>> -       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;
>>   }
>>
>> @@ -503,8 +525,14 @@ 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;
>>          }
>> @@ -526,7 +554,8 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
>>          return pool;
>>
>>   error:
>> -       free_percpu(pool->tfm);
>> +       free_percpu(pool->acomp_req);
>> +       free_percpu(pool->acomp);
>>          if (pool->zpool)
>>                  zpool_destroy_pool(pool->zpool);
>>          kfree(pool);
>> @@ -566,7 +595,8 @@ 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->acomp_req);
>> +       free_percpu(pool->acomp);
>>          zpool_destroy_pool(pool->zpool);
>>          kfree(pool);
>>   }
>> @@ -763,7 +793,8 @@ 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;
>>          u8 *src, *dst;
>>          unsigned int dlen;
>>          int ret;
>> @@ -803,14 +834,23 @@ 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);
>> +
>> +               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,
>> +                                          NULL, NULL);
>> +
>> +               ret = crypto_acomp_decompress(req);
> I assume all of these crypto_acomp_[compress|decompress] calls are
> actually synchronous,
> not asynchronous as the name suggests.  Otherwise, this would blow up
> quite spectacularly
> since all the resources we use in the call get derefed/unmapped below.
>
> Could an async algorithm be implement/used that would break this assumption?
>
> Seth
>
>> +
>> +               dlen = req->dlen;
>> +               put_cpu_ptr(entry->pool->acomp_req);
>>                  kunmap_atomic(dst);
>>                  zpool_unmap_handle(entry->pool->zpool, entry->handle);
>>                  BUG_ON(ret);
>> @@ -886,7 +926,8 @@ 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;
>>          int ret;
>>          unsigned int dlen = PAGE_SIZE, len;
>>          unsigned long handle;
>> @@ -925,12 +966,27 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
>>          }
>>
>>          /* compress */
>> +       req = *get_cpu_ptr(entry->pool->acomp_req);
>> +       if (!req) {
>> +               put_cpu_ptr(entry->pool->acomp_req);
>> +               ret = -EINVAL;
>> +               goto freepage;
>> +       }
>> +
>>          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, NULL,
>> +                                  NULL);
>> +
>> +       ret = crypto_acomp_compress(req);
>>          kunmap_atomic(src);
>> -       put_cpu_ptr(entry->pool->tfm);
>> +       put_cpu_ptr(entry->pool->acomp_req);
>> +       dlen = req->dlen;
>>          if (ret) {
>>                  ret = -EINVAL;
>>                  goto put_dstmem;
>> @@ -998,7 +1054,8 @@ 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;
>>          u8 *src, *dst;
>>          unsigned int dlen;
>>          int ret;
>> @@ -1014,13 +1071,25 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
>>          spin_unlock(&tree->lock);
>>
>>          /* decompress */
>> +       req = *get_cpu_ptr(entry->pool->acomp_req);
>> +       if (!req) {
>> +               put_cpu_ptr(entry->pool->acomp_req);
>> +               return -1;
>> +       }
>>          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, NULL,
>> +                                  NULL);
>> +
>> +       ret = crypto_acomp_decompress(req);
>> +
>> +       put_cpu_ptr(entry->pool->acomp_req);
>>          kunmap_atomic(dst);
>>          zpool_unmap_handle(entry->pool->zpool, entry->handle);
>>          BUG_ON(ret);
>> --
>> 1.8.3.1
>>
> .
>

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