[PATCH v6 12/16] mm: zswap: Allocate pool batching resources if the compressor supports batching.

[Kanchana P Sridhar]

This patch adds support for the per-CPU acomp_ctx to track multiple
compression/decompression requests. The zswap_cpu_comp_prepare() cpu
onlining code will check if the compressor supports batching. If so, it
will allocate the necessary batching resources.

However, zswap does not use more than one request yet. Follow-up patches
will actually utilize the multiple acomp_ctx requests/buffers for batch
compression/decompression of multiple pages.

The newly added ZSWAP_MAX_BATCH_SIZE limits the amount of extra memory used
for batching. There is no extra memory usage for compressors that do not
support batching.

Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
---
 mm/zswap.c | 132 +++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 98 insertions(+), 34 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index a2baceed3bf9..dc7d1ff04b22 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -78,6 +78,16 @@ static bool zswap_pool_reached_full;
 
 #define ZSWAP_PARAM_UNSET ""
 
+/*
+ * For compression batching of large folios:
+ * Maximum number of acomp compress requests that will be processed
+ * in a batch, iff the zswap compressor supports batching.
+ * This limit exists because we preallocate enough requests and buffers
+ * in the per-cpu acomp_ctx accordingly. Hence, a higher limit means higher
+ * memory usage.
+ */
+#define ZSWAP_MAX_BATCH_SIZE 8U
+
 static int zswap_setup(void);
 
 /* Enable/disable zswap */
@@ -143,9 +153,10 @@ bool zswap_never_enabled(void)
 
 struct crypto_acomp_ctx {
 	struct crypto_acomp *acomp;
-	struct acomp_req *req;
+	struct acomp_req **reqs;
+	u8 **buffers;
+	unsigned int nr_reqs;
 	struct crypto_wait wait;
-	u8 *buffer;
 	struct mutex mutex;
 	bool is_sleepable;
 };
@@ -821,15 +832,13 @@ 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_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
 	struct crypto_acomp *acomp = NULL;
-	struct acomp_req *req = NULL;
-	u8 *buffer = NULL;
-	int ret;
+	unsigned int nr_reqs = 1;
+	int ret = -ENOMEM;
+	int i;
 
-	buffer = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
-	if (!buffer) {
-		ret = -ENOMEM;
-		goto fail;
-	}
+	acomp_ctx->buffers = NULL;
+	acomp_ctx->reqs = NULL;
+	acomp_ctx->nr_reqs = 0;
 
 	acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
 	if (IS_ERR(acomp)) {
@@ -839,12 +848,30 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 		goto fail;
 	}
 
-	req = acomp_request_alloc(acomp);
-	if (!req) {
-		pr_err("could not alloc crypto acomp_request %s\n",
-		       pool->tfm_name);
-		ret = -ENOMEM;
+	if (acomp_has_async_batching(acomp))
+		nr_reqs = min(ZSWAP_MAX_BATCH_SIZE, crypto_acomp_batch_size(acomp));
+
+	acomp_ctx->buffers = kcalloc_node(nr_reqs, sizeof(u8 *), GFP_KERNEL, cpu_to_node(cpu));
+	if (!acomp_ctx->buffers)
+		goto fail;
+
+	for (i = 0; i < nr_reqs; ++i) {
+		acomp_ctx->buffers[i] = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
+		if (!acomp_ctx->buffers[i])
+			goto fail;
+	}
+
+	acomp_ctx->reqs = kcalloc_node(nr_reqs, sizeof(struct acomp_req *), GFP_KERNEL, cpu_to_node(cpu));
+	if (!acomp_ctx->reqs)
 		goto fail;
+
+	for (i = 0; i < nr_reqs; ++i) {
+		acomp_ctx->reqs[i] = acomp_request_alloc(acomp);
+		if (!acomp_ctx->reqs[i]) {
+			pr_err("could not alloc crypto acomp_request reqs[%d] %s\n",
+			       i, pool->tfm_name);
+			goto fail;
+		}
 	}
 
 	/*
@@ -853,6 +880,13 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 	 * again resulting in a deadlock.
 	 */
 	mutex_lock(&acomp_ctx->mutex);
+
+	/*
+	 * The crypto_wait is used only in fully synchronous, i.e., with scomp
+	 * or non-poll mode of acomp, hence there is only one "wait" per
+	 * acomp_ctx, with callback set to reqs[0], under the assumption that
+	 * there is at least 1 request per acomp_ctx.
+	 */
 	crypto_init_wait(&acomp_ctx->wait);
 
 	/*
@@ -860,20 +894,33 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 	 * 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,
+	acomp_request_set_callback(acomp_ctx->reqs[0], CRYPTO_TFM_REQ_MAY_BACKLOG,
 				   crypto_req_done, &acomp_ctx->wait);
 
-	acomp_ctx->buffer = buffer;
+	acomp_ctx->nr_reqs = nr_reqs;
 	acomp_ctx->acomp = acomp;
 	acomp_ctx->is_sleepable = acomp_is_async(acomp);
-	acomp_ctx->req = req;
 	mutex_unlock(&acomp_ctx->mutex);
 	return 0;
 
 fail:
+	if (acomp_ctx->buffers) {
+		for (i = 0; i < nr_reqs; ++i)
+			kfree(acomp_ctx->buffers[i]);
+		kfree(acomp_ctx->buffers);
+		acomp_ctx->buffers = NULL;
+	}
+
+	if (acomp_ctx->reqs) {
+		for (i = 0; i < nr_reqs; ++i)
+			if (!IS_ERR_OR_NULL(acomp_ctx->reqs[i]))
+				acomp_request_free(acomp_ctx->reqs[i]);
+		kfree(acomp_ctx->reqs);
+		acomp_ctx->reqs = NULL;
+	}
+
 	if (acomp)
 		crypto_free_acomp(acomp);
-	kfree(buffer);
 	return ret;
 }
 
@@ -883,14 +930,31 @@ static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 	struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
 
 	mutex_lock(&acomp_ctx->mutex);
+
 	if (!IS_ERR_OR_NULL(acomp_ctx)) {
-		if (!IS_ERR_OR_NULL(acomp_ctx->req))
-			acomp_request_free(acomp_ctx->req);
-		acomp_ctx->req = NULL;
+		int i;
+
+		if (acomp_ctx->reqs) {
+			for (i = 0; i < acomp_ctx->nr_reqs; ++i)
+				if (!IS_ERR_OR_NULL(acomp_ctx->reqs[i]))
+					acomp_request_free(acomp_ctx->reqs[i]);
+			kfree(acomp_ctx->reqs);
+			acomp_ctx->reqs = NULL;
+		}
+
+		if (acomp_ctx->buffers) {
+			for (i = 0; i < acomp_ctx->nr_reqs; ++i)
+				kfree(acomp_ctx->buffers[i]);
+			kfree(acomp_ctx->buffers);
+			acomp_ctx->buffers = NULL;
+		}
+
 		if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
 			crypto_free_acomp(acomp_ctx->acomp);
-		kfree(acomp_ctx->buffer);
+
+		acomp_ctx->nr_reqs = 0;
 	}
+
 	mutex_unlock(&acomp_ctx->mutex);
 
 	return 0;
@@ -903,7 +967,7 @@ static struct crypto_acomp_ctx *acomp_ctx_get_cpu_lock(struct zswap_pool *pool)
 	for (;;) {
 		acomp_ctx = raw_cpu_ptr(pool->acomp_ctx);
 		mutex_lock(&acomp_ctx->mutex);
-		if (likely(acomp_ctx->req))
+		if (likely(acomp_ctx->reqs))
 			return acomp_ctx;
 		/*
 		 * It is possible that we were migrated to a different CPU after
@@ -935,7 +999,7 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry,
 	u8 *dst;
 
 	acomp_ctx = acomp_ctx_get_cpu_lock(pool);
-	dst = acomp_ctx->buffer;
+	dst = acomp_ctx->buffers[0];
 	sg_init_table(&input, 1);
 	sg_set_page(&input, page, PAGE_SIZE, 0);
 
@@ -945,7 +1009,7 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry,
 	 * giving the dst buffer with enough length to avoid buffer overflow.
 	 */
 	sg_init_one(&output, dst, PAGE_SIZE * 2);
-	acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
+	acomp_request_set_params(acomp_ctx->reqs[0], &input, &output, PAGE_SIZE, dlen);
 
 	/*
 	 * it maybe looks a little bit silly that we send an asynchronous request,
@@ -959,8 +1023,8 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry,
 	 * but in different threads running on different cpu, we have different
 	 * acomp instance, so multiple threads can do (de)compression in parallel.
 	 */
-	comp_ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
-	dlen = acomp_ctx->req->dlen;
+	comp_ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->reqs[0]), &acomp_ctx->wait);
+	dlen = acomp_ctx->reqs[0]->dlen;
 	if (comp_ret)
 		goto unlock;
 
@@ -1011,19 +1075,19 @@ static void zswap_decompress(struct zswap_entry *entry, struct folio *folio)
 	 */
 	if ((acomp_ctx->is_sleepable && !zpool_can_sleep_mapped(zpool)) ||
 	    !virt_addr_valid(src)) {
-		memcpy(acomp_ctx->buffer, src, entry->length);
-		src = acomp_ctx->buffer;
+		memcpy(acomp_ctx->buffers[0], src, entry->length);
+		src = acomp_ctx->buffers[0];
 		zpool_unmap_handle(zpool, entry->handle);
 	}
 
 	sg_init_one(&input, src, entry->length);
 	sg_init_table(&output, 1);
 	sg_set_folio(&output, folio, PAGE_SIZE, 0);
-	acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, PAGE_SIZE);
-	BUG_ON(crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait));
-	BUG_ON(acomp_ctx->req->dlen != PAGE_SIZE);
+	acomp_request_set_params(acomp_ctx->reqs[0], &input, &output, entry->length, PAGE_SIZE);
+	BUG_ON(crypto_wait_req(crypto_acomp_decompress(acomp_ctx->reqs[0]), &acomp_ctx->wait));
+	BUG_ON(acomp_ctx->reqs[0]->dlen != PAGE_SIZE);
 
-	if (src != acomp_ctx->buffer)
+	if (src != acomp_ctx->buffers[0])
 		zpool_unmap_handle(zpool, entry->handle);
 	acomp_ctx_put_unlock(acomp_ctx);
 }
-- 
2.27.0