linux-kernel - [PATCH 09/15] mm/swap: avoid calling swp_swap_info when try to check SWP_STABLE

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Date:   Mon, 9 May 2022 21:14:10 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <willy@...radead.org>, <vbabka@...e.cz>, <dhowells@...hat.com>,
        <neilb@...e.de>, <apopple@...dia.com>, <david@...hat.com>,
        <surenb@...gle.com>, <peterx@...hat.com>,
        <naoya.horiguchi@....com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH 09/15] mm/swap: avoid calling swp_swap_info when try to check SWP_STABLE_WRITES

Use flags of si directly to check SWP_STABLE_WRITES to avoid possible
READ_ONCE and thus save some cpu cycles.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index 9c3e7e6ac202..89dd15504f3d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3892,7 +3892,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			 */
 			exclusive = true;
 		} else if (exclusive && PageWriteback(page) &&
-			  (swp_swap_info(entry)->flags & SWP_STABLE_WRITES)) {
+			  (si->flags & SWP_STABLE_WRITES)) {
 			/*
 			 * This is tricky: not all swap backends support
 			 * concurrent page modifications while under writeback.
-- 
2.23.0