linux-kernel - [PATCH] mm/vma: Do not register private-anon mappings with khugepaged during mmap

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Message-Id: <20250306063037.16299-1-dev.jain@arm.com>
Date: Thu,  6 Mar 2025 12:00:37 +0530
From: Dev Jain <dev.jain@....com>
To: akpm@...ux-foundation.org,
	Liam.Howlett@...cle.com,
	lorenzo.stoakes@...cle.com,
	vbabka@...e.cz,
	jannh@...gle.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: ryan.roberts@....com,
	anshuman.khandual@....com,
	aneesh.kumar@...nel.org,
	yang@...amperecomputing.com,
	david@...hat.com,
	willy@...radead.org,
	hughd@...gle.com,
	ziy@...dia.com,
	Dev Jain <dev.jain@....com>
Subject: [PATCH] mm/vma: Do not register private-anon mappings with khugepaged during mmap

We already are registering private-anon VMAs with khugepaged during fault
time, in do_huge_pmd_anonymous_page(). Commit "register suitable readonly
file vmas for khugepaged" moved the khugepaged registration logic from
shmem_mmap to the generic mmap path. Make this logic specific for non-anon
mappings.

Fixes: 613bec092fe7 ("mm: mmap: register suitable readonly file vmas for khugepaged")
Signed-off-by: Dev Jain <dev.jain@....com>
---
 mm/vma.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vma.c b/mm/vma.c
index af1d549b179c..730a26bf14a5 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -2377,7 +2377,8 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap)
 	 * vma_merge_new_range() calls khugepaged_enter_vma() too, the below
 	 * call covers the non-merge case.
 	 */
-	khugepaged_enter_vma(vma, map->flags);
+	if (!vma_is_anonymous(vma))
+		khugepaged_enter_vma(vma, map->flags);
 	ksm_add_vma(vma);
 	*vmap = vma;
 	return 0;
-- 
2.30.2