On Tue, Aug 18, 2020 at 2:34 PM Barry Song <song.bao.hua@xxxxxxxxxxxxx> wrote:
>
> Right now, all new ZIP drivers are adapted to crypto_acomp APIs rather
> than legacy crypto_comp APIs. Tradiontal ZIP drivers like lz4,lzo etc
> have been also wrapped into acomp via scomp backend. But zswap.c is still
> using the old APIs. That means zswap won't be able to work on any new
> ZIP drivers in kernel.
>
> This patch moves to use cryto_acomp APIs to fix the disconnected bridge
> between new ZIP drivers and zswap. It is probably the first real user
> to use acomp but perhaps not a good example to demonstrate how multiple
> acomp requests can be executed in parallel in one acomp instance.
> frontswap is doing page load and store page by page synchronously.
> swap_writepage() depends on the completion of frontswap_store() to
> decide if it should call __swap_writepage() to swap to disk.
>
> However this patch creates multiple acomp instances, so multiple threads
> running on multiple different cpus can actually do (de)compression
> parallelly, leveraging the power of multiple ZIP hardware queues. This
> is also consistent with frontswap's page management model.
>
> The old zswap code uses atomic context and avoids the race conditions
> while shared resources like zswap_dstmem are accessed. Here since acomp
> can sleep, per-cpu mutex is used to replace preemption-disable.
>
> While it is possible to make mm/page_io.c and mm/frontswap.c support
> async (de)compression in some way, the entire design requires careful
> thinking and performance evaluation. For the first step, the base with
> fixed connection between ZIP drivers and zswap should be built.
>
> Cc: Luis Claudio R. Goncalves <lgoncalv@xxxxxxxxxx>
> Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> Cc: Mahipal Challa <mahipalreddy2006@xxxxxxxxx>
> Cc: Seth Jennings <sjenning@xxxxxxxxxx>
> Cc: Dan Streetman <ddstreet@xxxxxxxx>
> Cc: Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>
> Cc: Zhou Wang <wangzhou1@xxxxxxxxxxxxx>
> Cc: Hao Fang <fanghao11@xxxxxxxxxx>
> Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
Acked-by: Vitaly Wool <vitalywool@xxxxxxxxx>
> ---
> -v6:
> * rebase on top of 5.9-rc1;
> * move to crypto_alloc_acomp_node() API to use local ZIP hardware
>
> mm/zswap.c | 183 ++++++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 138 insertions(+), 45 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index fbb782924ccc..00b5f14a7332 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -24,8 +24,10 @@
> #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>
> @@ -127,9 +129,17 @@ module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
> * data structures
> **********************************/
>
> +struct crypto_acomp_ctx {
> + struct crypto_acomp *acomp;
> + struct acomp_req *req;
> + struct crypto_wait wait;
> + u8 *dstmem;
> + struct mutex *mutex;
> +};
> +
> struct zswap_pool {
> struct zpool *zpool;
> - struct crypto_comp * __percpu *tfm;
> + struct crypto_acomp_ctx __percpu *acomp_ctx;
> struct kref kref;
> struct list_head list;
> struct work_struct release_work;
> @@ -388,23 +398,43 @@ static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
> * per-cpu code
> **********************************/
> static DEFINE_PER_CPU(u8 *, zswap_dstmem);
> +/*
> + * If users dynamically change the zpool type and compressor at runtime, i.e.
> + * zswap is running, zswap can have more than one zpool on one cpu, but they
> + * are sharing dtsmem. So we need this mutex to be per-cpu.
> + */
> +static DEFINE_PER_CPU(struct mutex *, zswap_mutex);
>
> static int zswap_dstmem_prepare(unsigned int cpu)
> {
> + struct mutex *mutex;
> u8 *dst;
>
> dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
> if (!dst)
> return -ENOMEM;
>
> + mutex = kmalloc_node(sizeof(*mutex), GFP_KERNEL, cpu_to_node(cpu));
> + if (!mutex) {
> + kfree(dst);
> + return -ENOMEM;
> + }
> +
> + mutex_init(mutex);
> per_cpu(zswap_dstmem, cpu) = dst;
> + per_cpu(zswap_mutex, cpu) = mutex;
> return 0;
> }
>
> static int zswap_dstmem_dead(unsigned int cpu)
> {
> + struct mutex *mutex;
> u8 *dst;
>
> + mutex = per_cpu(zswap_mutex, cpu);
> + kfree(mutex);
> + per_cpu(zswap_mutex, cpu) = NULL;
> +
> dst = per_cpu(zswap_dstmem, cpu);
> kfree(dst);
> per_cpu(zswap_dstmem, cpu) = NULL;
> @@ -415,30 +445,54 @@ 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;
> -
> - if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
> - return 0;
> + struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
> + struct crypto_acomp *acomp;
> + struct acomp_req *req;
> +
> + acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
> + if (IS_ERR(acomp)) {
> + pr_err("could not alloc crypto acomp %s : %ld\n",
> + pool->tfm_name, PTR_ERR(acomp));
> + return PTR_ERR(acomp);
> + }
> + acomp_ctx->acomp = 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));
> + req = acomp_request_alloc(acomp_ctx->acomp);
> + if (!req) {
> + pr_err("could not alloc crypto acomp_request %s\n",
> + pool->tfm_name);
> + crypto_free_acomp(acomp_ctx->acomp);
> return -ENOMEM;
> }
> - *per_cpu_ptr(pool->tfm, cpu) = tfm;
> + acomp_ctx->req = req;
> +
> + crypto_init_wait(&acomp_ctx->wait);
> + /*
> + * if the backend of acomp is async zip, crypto_req_done() will wakeup
> + * crypto_wait_req(); if the backend of acomp is scomp, the callback
> + * won't be called, crypto_wait_req() will return without blocking.
> + */
> + acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
> + crypto_req_done, &acomp_ctx->wait);
> +
> + acomp_ctx->mutex = per_cpu(zswap_mutex, cpu);
> + acomp_ctx->dstmem = per_cpu(zswap_dstmem, cpu);
> +
> 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_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
> +
> + if (!IS_ERR_OR_NULL(acomp_ctx)) {
> + if (!IS_ERR_OR_NULL(acomp_ctx->req))
> + acomp_request_free(acomp_ctx->req);
> + if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
> + crypto_free_acomp(acomp_ctx->acomp);
> + }
>
> - 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;
> }
>
> @@ -561,8 +615,9 @@ 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_ctx = alloc_percpu(*pool->acomp_ctx);
> + if (!pool->acomp_ctx) {
> pr_err("percpu alloc failed\n");
> goto error;
> }
> @@ -585,7 +640,8 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
> return pool;
>
> error:
> - free_percpu(pool->tfm);
> + if (pool->acomp_ctx)
> + free_percpu(pool->acomp_ctx);
> if (pool->zpool)
> zpool_destroy_pool(pool->zpool);
> kfree(pool);
> @@ -596,14 +652,14 @@ static __init struct zswap_pool *__zswap_pool_create_fallback(void)
> {
> bool has_comp, has_zpool;
>
> - has_comp = crypto_has_comp(zswap_compressor, 0, 0);
> + has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
> if (!has_comp && strcmp(zswap_compressor,
> CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
> pr_err("compressor %s not available, using default %s\n",
> zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
> param_free_charp(&zswap_compressor);
> zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
> - has_comp = crypto_has_comp(zswap_compressor, 0, 0);
> + has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
> }
> if (!has_comp) {
> pr_err("default compressor %s not available\n",
> @@ -639,7 +695,7 @@ 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_ctx);
> zpool_destroy_pool(pool->zpool);
> kfree(pool);
> }
> @@ -723,7 +779,7 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp,
> }
> type = s;
> } else if (!compressor) {
> - if (!crypto_has_comp(s, 0, 0)) {
> + if (!crypto_has_acomp(s, 0, 0)) {
> pr_err("compressor %s not available\n", s);
> return -ENOENT;
> }
> @@ -774,7 +830,7 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp,
> * failed, maybe both compressor and zpool params were bad.
> * Allow changing this param, so pool creation will succeed
> * when the other param is changed. We already verified this
> - * param is ok in the zpool_has_pool() or crypto_has_comp()
> + * param is ok in the zpool_has_pool() or crypto_has_acomp()
> * checks above.
> */
> ret = param_set_charp(s, kp);
> @@ -876,7 +932,9 @@ 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 crypto_acomp_ctx *acomp_ctx;
> +
> u8 *src, *dst;
> unsigned int dlen;
> int ret;
> @@ -916,14 +974,21 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
>
> case ZSWAP_SWAPCACHE_NEW: /* page is locked */
> /* decompress */
> + acomp_ctx = this_cpu_ptr(entry->pool->acomp_ctx);
> +
> dlen = PAGE_SIZE;
> src = (u8 *)zhdr + 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);
> - kunmap_atomic(dst);
> + dst = kmap(page);
> +
> + mutex_lock(acomp_ctx->mutex);
> + sg_init_one(&input, src, entry->length);
> + sg_init_one(&output, dst, dlen);
> + acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
> + ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
> + dlen = acomp_ctx->req->dlen;
> + mutex_unlock(acomp_ctx->mutex);
> +
> + kunmap(page);
> BUG_ON(ret);
> BUG_ON(dlen != PAGE_SIZE);
>
> @@ -1004,7 +1069,8 @@ 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 crypto_acomp_ctx *acomp_ctx;
> int ret;
> unsigned int hlen, dlen = PAGE_SIZE;
> unsigned long handle, value;
> @@ -1074,12 +1140,32 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
> }
>
> /* compress */
> - 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);
> - kunmap_atomic(src);
> - put_cpu_ptr(entry->pool->tfm);
> + acomp_ctx = this_cpu_ptr(entry->pool->acomp_ctx);
> +
> + mutex_lock(acomp_ctx->mutex);
> +
> + src = kmap(page);
> + dst = acomp_ctx->dstmem;
> + 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(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
> + /*
> + * it maybe looks a little bit silly that we send an asynchronous request,
> + * then wait for its completion synchronously. This makes the process look
> + * synchronous in fact.
> + * Theoretically, acomp supports users send multiple acomp requests in one
> + * acomp instance, then get those requests done simultaneously. but in this
> + * case, frontswap actually does store and load page by page, there is no
> + * existing method to send the second page before the first page is done
> + * in one thread doing frontswap.
> + * but in different threads running on different cpu, we have different
> + * acomp instance, so multiple threads can do (de)compression in parallel.
> + */
> + ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
> + dlen = acomp_ctx->req->dlen;
> + kunmap(page);
> +
> if (ret) {
> ret = -EINVAL;
> goto put_dstmem;
> @@ -1103,7 +1189,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
> memcpy(buf, &zhdr, hlen);
> memcpy(buf + hlen, dst, dlen);
> zpool_unmap_handle(entry->pool->zpool, handle);
> - put_cpu_var(zswap_dstmem);
> + mutex_unlock(acomp_ctx->mutex);
>
> /* populate entry */
> entry->offset = offset;
> @@ -1131,7 +1217,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
> return 0;
>
> put_dstmem:
> - put_cpu_var(zswap_dstmem);
> + mutex_unlock(acomp_ctx->mutex);
> zswap_pool_put(entry->pool);
> freepage:
> zswap_entry_cache_free(entry);
> @@ -1148,7 +1234,8 @@ 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 crypto_acomp_ctx *acomp_ctx;
> u8 *src, *dst;
> unsigned int dlen;
> int ret;
> @@ -1175,11 +1262,17 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
> src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
> if (zpool_evictable(entry->pool->zpool))
> src += 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);
> - kunmap_atomic(dst);
> + dst = kmap(page);
> +
> + acomp_ctx = this_cpu_ptr(entry->pool->acomp_ctx);
> + mutex_lock(acomp_ctx->mutex);
> + sg_init_one(&input, src, entry->length);
> + sg_init_one(&output, dst, dlen);
> + acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
> + ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
> + mutex_unlock(acomp_ctx->mutex);
> +
> + kunmap(page);
> zpool_unmap_handle(entry->pool->zpool, entry->handle);
> BUG_ON(ret);
>
> --
> 2.27.0
>
>
