Commit 0b1bf60c authored by Nhat Pham's avatar Nhat Pham Committed by Andrew Morton
Browse files

mm/zswap: reduce the size of the compression buffer to a single page 

Reduce the compression buffer size from 2 * PAGE_SIZE to only one page, as
the compression output (in the success case) should not exceed the length
of the input.

In the past, Chengming tried to reduce the compression buffer size, but
ran into issues with the LZO algorithm (see [2]).  Herbert Xu reported
that the issue has been fixed (see [3]).  Now we should have the guarantee
that compressors' output should not exceed one page in the success case,
and the algorithm will just report failure otherwise.

With this patch, we save one page per cpu (per compression algorithm).

Link: https://lkml.kernel.org/r/20250820181547.3794167-1-nphamcs@gmail.com
Link: https://lore.kernel.org/linux-mm/20231213-zswap-dstmem-v4-1-f228b059dd89@bytedance.com/ [1]
Link: https://lore.kernel.org/lkml/0000000000000b05cd060d6b5511@google.com/ [2]
Link: https://lore.kernel.org/linux-mm/aKUmyl5gUFCdXGn-@gondor.apana.org.au/

 [3]
Co-developed-by: default avatarChengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: default avatarChengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: default avatarNhat Pham <nphamcs@gmail.com>
Acked-by: default avatarSeongJae Park <sj@kernel.org>
Reviewed-by: default avatarChengming Zhou <chengming.zhou@linux.dev>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 0cd01c4a

mm/zswap.c

+2 −7
Original line number Diff line number Diff line
@@ -831,7 +831,7 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node) 
	u8 *buffer = NULL;

	int ret;



	buffer = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));

	buffer = kmalloc_node(PAGE_SIZE, GFP_KERNEL, cpu_to_node(cpu));

	if (!buffer) {

		ret = -ENOMEM;

		goto fail;
@@ -959,12 +959,7 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry, 
	sg_init_table(&input, 1);

	sg_set_page(&input, page, PAGE_SIZE, 0);



	/*

	 * 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);

	sg_init_one(&output, dst, PAGE_SIZE);

	acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);



	/*