Hi Dan,
Thanks for your reply.
On Sat, Feb 25, 2017 at 3:51 AM, Dan Streetman <ddstreet@xxxxxxxx> wrote:
> On Fri, Feb 24, 2017 at 11:05 AM, Mahipal Challa
> <Mahipal.Challa@xxxxxxxxxx> 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?
1) The new crypto acomp/scomp framework, provides both synchronous and
asynchronous comp/decomp
functionality with the same async-crypto(acomp) api(include/crypto/acompress.h).
2) Currently with new crypto acomp/scomp framework, the crypto
sub-system(crypto/lzo.c, crypto/deflate.c)
only supports synchronous mode of compression/decompression which
meets the zswap requirement.
3) The new crypto acomp/scomp framework is introduced in the 4.10.xx kernel.
With this new framework, according to Herbert Xu, existing crypto
comp(CRYPTO_ALG_TYPE_COMPRESS ) api
is going to be deprecated (which zswap uses).
4) Applications like zswap, which use comp/decomp of crypto subsystem,
at some point will have to be ported to
the new framework.
Regards,
-Mahipal
>> Signed-off-by: Mahipal Challa <Mahipal.Challa@xxxxxxxxxx>
>> Signed-off-by: Vishnu Nair <Vishnu.Nair@xxxxxxxxxx>
>> ---
>> 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@xxxxxxxxxxxxxx>");
>> MODULE_DESCRIPTION("Compressed cache for swap pages");
>> +
>> --
>> 1.8.3.1
>>
>
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