linux-kernel - [RFC PATCH 3/3] mm/mincore: avoid touching the PTL

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Message-ID: <20250807152720.62032-4-ryncsn@gmail.com>
Date: Thu,  7 Aug 2025 23:27:20 +0800
From: Kairui Song <ryncsn@...il.com>
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Jann Horn <jannh@...gle.com>,
	Pedro Falcato <pfalcato@...e.de>,
	Matthew Wilcox <willy@...radead.org>,
	Hugh Dickins <hughd@...gle.com>,
	David Hildenbrand <david@...hat.com>,
	Chris Li <chrisl@...nel.org>,
	Barry Song <baohua@...nel.org>,
	Baoquan He <bhe@...hat.com>,
	Nhat Pham <nphamcs@...il.com>,
	Kemeng Shi <shikemeng@...weicloud.com>,
	linux-kernel@...r.kernel.org,
	Kairui Song <kasong@...cent.com>
Subject: [RFC PATCH 3/3] mm/mincore: avoid touching the PTL

From: Kairui Song <kasong@...cent.com>

mincore only interested in the existence of a page, which is a
changing state by nature, locking and making it stable is not needed.
And now neither mincore_page or mincore_swap requires PTL, this PTL
locking can be dropped.

Signed-off-by: Kairui Song <kasong@...cent.com>
---
 mm/mincore.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/mincore.c b/mm/mincore.c
index 1ac53acac239..cc4460aba1f9 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -153,13 +153,13 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 		goto out;
 	}
 
-	ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+	ptep = pte_offset_map(pmd, addr);
 	if (!ptep) {
 		walk->action = ACTION_AGAIN;
 		return 0;
 	}
 	for (; addr != end; ptep += step, addr += step * PAGE_SIZE) {
-		pte_t pte = ptep_get(ptep);
+		pte_t pte = ptep_get_lockless(ptep);
 
 		step = 1;
 		/* We need to do cache lookup too for pte markers */
@@ -192,7 +192,7 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 		}
 		vec += step;
 	}
-	pte_unmap_unlock(ptep - 1, ptl);
+	pte_unmap(ptep - 1);
 out:
 	walk->private += nr;
 	cond_resched();
-- 
2.50.1