Message-Id: <20231213-zswap-dstmem-v5-5-9382162bbf05@bytedance.com>
Date: Thu, 28 Dec 2023 09:45:46 +0000
From: Chengming Zhou <zhouchengming@...edance.com>
To: Barry Song <21cnbao@...il.com>, Yosry Ahmed <yosryahmed@...gle.com>, Nhat Pham <nphamcs@...il.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Dan Streetman <ddstreet@...e.org>, Vitaly Wool <vitaly.wool@...sulko.com>,
 Johannes Weiner <hannes@...xchg.org>, Chris Li <chriscli@...gle.com>, Seth Jennings <sjenning@...hat.com>
Cc: Yosry Ahmed <yosryahmed@...gle.com>, Nhat Pham <nphamcs@...il.com>, Chris Li <chrisl@...nel.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Chengming Zhou <zhouchengming@...edance.com>
Subject: [PATCH v5 5/5] mm/zswap: change per-cpu mutex and buffer to per-acomp_ctx

First of all, we need to rename acomp_ctx->dstmem field to buffer,
since we are now using for purposes other than compression.

Then we change per-cpu mutex and buffer to per-acomp_ctx, since
them belong to the acomp_ctx and are necessary parts when used
in the compress/decompress contexts.

So we can remove the old per-cpu mutex and dstmem.

Acked-by: Chris Li <chrisl@...nel.org> (Google)
Reviewed-by: Nhat Pham <nphamcs@...il.com>
Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 include/linux/cpuhotplug.h |   1 -
 mm/zswap.c                 | 104 ++++++++++++++-------------------------------
 2 files changed, 33 insertions(+), 72 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index efc0c0b07efb..c3e06e21766a 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -124,7 +124,6 @@ enum cpuhp_state {
 	CPUHP_ARM_BL_PREPARE,
 	CPUHP_TRACE_RB_PREPARE,
 	CPUHP_MM_ZS_PREPARE,
-	CPUHP_MM_ZSWP_MEM_PREPARE,
 	CPUHP_MM_ZSWP_POOL_PREPARE,
 	CPUHP_KVM_PPC_BOOK3S_PREPARE,
 	CPUHP_ZCOMP_PREPARE,
diff --git a/mm/zswap.c b/mm/zswap.c
index e756b2af838b..7c18755c6e1c 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -166,8 +166,8 @@ struct crypto_acomp_ctx {
 	struct crypto_acomp *acomp;
 	struct acomp_req *req;
 	struct crypto_wait wait;
-	u8 *dstmem;
-	struct mutex *mutex;
+	u8 *buffer;
+	struct mutex mutex;
 };
 
 /*
@@ -694,63 +694,26 @@ static void zswap_alloc_shrinker(struct zswap_pool *pool)
 /*********************************
 * 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;
-
-	return 0;
-}
-
 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;
 	struct acomp_req *req;
+	int ret;
+
+	mutex_init(&acomp_ctx->mutex);
+
+	acomp_ctx->buffer = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
+	if (!acomp_ctx->buffer)
+		return -ENOMEM;
 
 	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);
+		ret = PTR_ERR(acomp);
+		goto acomp_fail;
 	}
 	acomp_ctx->acomp = acomp;
 
@@ -758,8 +721,8 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 	if (!req) {
 		pr_err("could not alloc crypto acomp_request %s\n",
 		       pool->tfm_name);
-		crypto_free_acomp(acomp_ctx->acomp);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto req_fail;
 	}
 	acomp_ctx->req = req;
 
@@ -772,10 +735,13 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 	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;
+
+req_fail:
+	crypto_free_acomp(acomp_ctx->acomp);
+acomp_fail:
+	kfree(acomp_ctx->buffer);
+	return ret;
 }
 
 static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
@@ -788,6 +754,7 @@ static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 			acomp_request_free(acomp_ctx->req);
 		if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
 			crypto_free_acomp(acomp_ctx->acomp);
+		kfree(acomp_ctx->buffer);
 	}
 
 	return 0;
@@ -1400,12 +1367,12 @@ static void __zswap_load(struct zswap_entry *entry, struct page *page)
 	u8 *src;
 
 	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
-	mutex_lock(acomp_ctx->mutex);
+	mutex_lock(&acomp_ctx->mutex);
 
 	src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
 	if (!zpool_can_sleep_mapped(zpool)) {
-		memcpy(acomp_ctx->dstmem, src, entry->length);
-		src = acomp_ctx->dstmem;
+		memcpy(acomp_ctx->buffer, src, entry->length);
+		src = acomp_ctx->buffer;
 		zpool_unmap_handle(zpool, entry->handle);
 	}
 
@@ -1415,7 +1382,7 @@ static void __zswap_load(struct zswap_entry *entry, struct page *page)
 	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);
-	mutex_unlock(acomp_ctx->mutex);
+	mutex_unlock(&acomp_ctx->mutex);
 
 	if (zpool_can_sleep_mapped(zpool))
 		zpool_unmap_handle(zpool, entry->handle);
@@ -1636,13 +1603,17 @@ bool zswap_store(struct folio *folio)
 	/* compress */
 	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
 
-	mutex_lock(acomp_ctx->mutex);
+	mutex_lock(&acomp_ctx->mutex);
 
-	dst = acomp_ctx->dstmem;
+	dst = acomp_ctx->buffer;
 	sg_init_table(&input, 1);
 	sg_set_page(&input, page, PAGE_SIZE, 0);
 
-	/* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
+	/*
+	 * We need PAGE_SIZE * 2 here since there maybe over-compression case,
+	 * and hardware-accelerators may won't check the dst buffer size, so
+	 * 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);
 	/*
@@ -1682,7 +1653,7 @@ bool zswap_store(struct folio *folio)
 	buf = zpool_map_handle(zpool, handle, ZPOOL_MM_WO);
 	memcpy(buf, dst, dlen);
 	zpool_unmap_handle(zpool, handle);
-	mutex_unlock(acomp_ctx->mutex);
+	mutex_unlock(&acomp_ctx->mutex);
 
 	/* populate entry */
 	entry->swpentry = swp_entry(type, offset);
@@ -1725,7 +1696,7 @@ bool zswap_store(struct folio *folio)
 	return true;
 
 put_dstmem:
-	mutex_unlock(acomp_ctx->mutex);
+	mutex_unlock(&acomp_ctx->mutex);
 put_pool:
 	zswap_pool_put(entry->pool);
 freepage:
@@ -1900,13 +1871,6 @@ static int zswap_setup(void)
 		goto cache_fail;
 	}
 
-	ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
-				zswap_dstmem_prepare, zswap_dstmem_dead);
-	if (ret) {
-		pr_err("dstmem alloc failed\n");
-		goto dstmem_fail;
-	}
-
 	ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
 				      "mm/zswap_pool:prepare",
 				      zswap_cpu_comp_prepare,
@@ -1938,8 +1902,6 @@ static int zswap_setup(void)
 	if (pool)
 		zswap_pool_destroy(pool);
 hp_fail:
-	cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
-dstmem_fail:
 	kmem_cache_destroy(zswap_entry_cache);
 cache_fail:
 	/* if built-in, we aren't unloaded on failure; don't allow use */

-- 
b4 0.10.1

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