From 8c6ff7f181786d0b296bb0f1bf269ca8770632c9 Mon Sep 17 00:00:00 2001 From: Dev Jain Date: Thu, 6 Mar 2025 12:00:37 +0530 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. The userspace-visible effect should be this: khugepaged will unnecessarily scan mm's which haven't yet faulted in. Note that it won't actually collapse because all PTEs are none. Now that I think about it, the mm is going to have a file VMA anyways during fork+exec, so the mm already gets registered during mmap due to the non-anon case (I *think*), so at least one of either the mmap registration or fault-time registration is redundant. Make this logic specific for non-anon mappings. Link: https://lkml.kernel.org/r/20250306063037.16299-1-dev.jain@arm.com Fixes: 613bec092fe7 ("mm: mmap: register suitable readonly file vmas for khugepaged") Signed-off-by: Dev Jain Cc: "Aneesh Kumar K.V" Cc: Anshuman Khandual Cc: David Hildenbrand Cc: Hugh Dickins Cc: Jann Horn Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcow (Oracle) Cc: Ryan Roberts Cc: Vlastimil Babka Cc: Yang Shi Cc: Zi Yan Signed-off-by: Andrew Morton --- mm/vma.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/vma.c b/mm/vma.c index 96bcb372c90e4..71ca012c616c9 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -2381,7 +2381,8 @@ 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; -- 2.39.5