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

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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@xxxxxxxxx> wrote:
This adds the support for kernel's crypto new acomp/scomp framework
to zswap.

Signed-off-by: Mahipal Challa <Mahipal.Challa@xxxxxxxxxx>
Signed-off-by: Vishnu Nair <Vishnu.Nair@xxxxxxxxxx>
---
  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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