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From: Barry Song <21cnbao@gmail.com>
To: akpm@linux-foundation.org,
	davem@davemloft.net,
	hannes@cmpxchg.org,
	herbert@gondor.apana.org.au,
	linux-crypto@vger.kernel.org,
	linux-mm@kvack.org,
	nphamcs@gmail.com,
	yosryahmed@google.com,
	zhouchengming@bytedance.com
Cc: chriscli@google.com,
	chrisl@kernel.org,
	ddstreet@ieee.org,
	linux-kernel@vger.kernel.org,
	sjenning@redhat.com,
	vitaly.wool@konsulko.com,
	Barry Song <v-songbaohua@oppo.com>
Subject: [PATCH v2 2/3] mm/zswap: remove the memcpy if acomp is not sleepable
Date: Fri, 16 Feb 2024 17:08:14 +1300
Message-Id: <20240216040815.114202-3-21cnbao@gmail.com>
In-Reply-To: <20240216040815.114202-1-21cnbao@gmail.com>
References: <20240216040815.114202-1-21cnbao@gmail.com>
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From: Barry Song <v-songbaohua@oppo.com>

Most compressors are actually CPU-based and won't sleep during
compression and decompression. We should remove the redundant
memcpy for them.

Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Tested-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
---
 mm/zswap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 350dd2fc8159..6319d2281020 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -168,6 +168,7 @@ struct crypto_acomp_ctx {
 	struct crypto_wait wait;
 	u8 *buffer;
 	struct mutex mutex;
+	bool is_sleepable;
 };
 
 /*
@@ -716,6 +717,7 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 		goto acomp_fail;
 	}
 	acomp_ctx->acomp = acomp;
+	acomp_ctx->is_sleepable = acomp_is_sleepable(acomp);
 
 	req = acomp_request_alloc(acomp_ctx->acomp);
 	if (!req) {
@@ -1368,7 +1370,7 @@ static void __zswap_load(struct zswap_entry *entry, struct page *page)
 	mutex_lock(&acomp_ctx->mutex);
 
 	src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
-	if (!zpool_can_sleep_mapped(zpool)) {
+	if (acomp_ctx->is_sleepable && !zpool_can_sleep_mapped(zpool)) {
 		memcpy(acomp_ctx->buffer, src, entry->length);
 		src = acomp_ctx->buffer;
 		zpool_unmap_handle(zpool, entry->handle);
@@ -1382,7 +1384,7 @@ static void __zswap_load(struct zswap_entry *entry, struct page *page)
 	BUG_ON(acomp_ctx->req->dlen != PAGE_SIZE);
 	mutex_unlock(&acomp_ctx->mutex);
 
-	if (zpool_can_sleep_mapped(zpool))
+	if (!acomp_ctx->is_sleepable || zpool_can_sleep_mapped(zpool))
 		zpool_unmap_handle(zpool, entry->handle);
 }
 
-- 
2.34.1