linux-kernel - [PATCH] mm/memcg: use get_page() for device private pages in mc_handle_swap

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Message-ID: <20230715032802.2508163-1-linmiaohe@huawei.com>
Date:   Sat, 15 Jul 2023 11:28:02 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <hannes@...xchg.org>,
        <mhocko@...nel.org>, <roman.gushchin@...ux.dev>,
        <shakeelb@...gle.com>
CC:     <muchun.song@...ux.dev>, <linux-mm@...ck.org>,
        <cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] mm/memcg: use get_page() for device private pages in mc_handle_swap_pte()

When page table locked is held, the page can't be freed from under us.
So use get_page() to get the extra page reference to simplify the code.
No functional change intended.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/memcontrol.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 93e3cc581b51..4ca382efb1ca 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5670,8 +5670,9 @@ static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
 	 */
 	if (is_device_private_entry(ent)) {
 		page = pfn_swap_entry_to_page(ent);
-		if (!get_page_unless_zero(page))
-			return NULL;
+		/* Get a page reference while we know the page can't be freed. */
+		get_page(page);
+
 		return page;
 	}
 
-- 
2.33.0