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Message-ID: <CALZtONBuQJN3Qrd-RP4_TAD=OeWNO8quPYpN+=Gsz2byAxWFPg@mail.gmail.com>
Date: Wed, 8 Mar 2017 12:38:40 -0500
From: Dan Streetman <ddstreet@...e.org>
To: Mahipal Reddy <mahipalreddy2006@...il.com>
Cc: Mahipal Challa <Mahipal.Challa@...ium.com>,
Seth Jennings <sjenning@...hat.com>,
Linux-MM <linux-mm@...ck.org>,
Herbert Xu <herbert@...dor.apana.org.au>,
linux-kernel <linux-kernel@...r.kernel.org>, pathreya@...ium.com,
Vishnu Nair <Vishnu.Nair@...ium.com>
Subject: Re: [PATCH v2 1/1] mm: zswap - Add crypto acomp/scomp framework support
On Mon, Feb 27, 2017 at 9:40 AM, Mahipal Reddy
<mahipalreddy2006@...il.com> wrote:
> Hi Dan,
> Thanks for your reply.
>
> On Sat, Feb 25, 2017 at 3:51 AM, Dan Streetman <ddstreet@...e.org> wrote:
>> On Fri, Feb 24, 2017 at 11:05 AM, Mahipal Challa
>> <Mahipal.Challa@...ium.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?
>
> 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).
zswap gets the fun of being the first crypto compression consumer to
switch to the new api? ;-)
It looks like the crypto_scomp interface is buried under
include/crypto/internal/scompress.h, however that's exactly what zswap
should be using. We don't need to switch to an asynchronous interface
that's rather significantly more complicated, and then use it in a
synchronous way. The crypto_scomp interface should probably be made
public, not an implementation internal.
>
> 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@...ium.com>
>>> Signed-off-by: Vishnu Nair <Vishnu.Nair@...ium.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@...iantweb.net>");
>>> MODULE_DESCRIPTION("Compressed cache for swap pages");
>>> +
>>> --
>>> 1.8.3.1
>>>
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@...ck.org. For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
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