[106/192] mm/zswap.c: avoid unnecessary copy-in at map time

Commit Message

Andrew Morton July 1, 2021, 1:52 a.m. UTC

From: Miaohe Lin <[e-mail]>
Subject: mm/zswap.c: avoid unnecessary copy-in at map time

The buf mapped via zpool_map_handle() is only used to store compressed
page buffer and there is no information to extract from it. So we could
use ZPOOL_MM_WO instead to avoid unnecessary copy-in at map time.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Miaohe Lin <[e-mail]>
Cc: Colin Ian King <[e-mail]>
Cc: Dan Streetman <[e-mail]>
Cc: Nathan Chancellor <[e-mail]>
Cc: Sebastian Andrzej Siewior <[e-mail]>
Cc: Seth Jennings <[e-mail]>
Cc: Tian Tao <[e-mail]>
Cc: Vitaly Wool <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/zswap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

--- a/mm/zswap.c~mm-zswapc-avoid-unnecessary-copy-in-at-map-time
+++ a/mm/zswap.c
@@ -1203,7 +1203,7 @@  static int zswap_frontswap_store(unsigne
 		zswap_reject_alloc_fail++;
 		goto put_dstmem;
 	}
-	buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
+	buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_WO);
 	memcpy(buf, &zhdr, hlen);
 	memcpy(buf + hlen, dst, dlen);
 	zpool_unmap_handle(entry->pool->zpool, handle);