The patch titled
Subject: mm/hugetlb: make hugetlb_follow_page_mask() safe to pmd unshare
has been added to the -mm mm-unstable branch. Its filename is
mm-hugetlb-make-hugetlb_follow_page_mask-safe-to-pmd-unshare.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-make-hugetlb_follow_page_mask-safe-to-pmd-unshare.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm/hugetlb: make hugetlb_follow_page_mask() safe to pmd unshare
Date: Fri, 16 Dec 2022 10:52:19 -0500
Since hugetlb_follow_page_mask() walks the pgtable, it needs the vma lock
to make sure the pgtable page will not be freed concurrently.
Link: https://lkml.kernel.org/r/20221216155219.2043714-1-peterx@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: James Houghton <jthoughton@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/hugetlb.c~mm-hugetlb-make-hugetlb_follow_page_mask-safe-to-pmd-unshare
+++ a/mm/hugetlb.c
@@ -6375,9 +6375,10 @@ struct page *hugetlb_follow_page_mask(st
if (WARN_ON_ONCE(flags & FOLL_PIN))
return NULL;
+ hugetlb_vma_lock_read(vma);
pte = huge_pte_offset(mm, haddr, huge_page_size(h));
if (!pte)
- return NULL;
+ goto out_unlock;
ptl = huge_pte_lock(h, mm, pte);
entry = huge_ptep_get(pte);
@@ -6400,6 +6401,8 @@ struct page *hugetlb_follow_page_mask(st
}
out:
spin_unlock(ptl);
+out_unlock:
+ hugetlb_vma_unlock_read(vma);
return page;
}
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-uffd-fix-pte-marker-when-fork-without-fork-event.patch
mm-fix-a-few-rare-cases-of-using-swapin-error-pte-marker.patch
mm-uffd-always-wr-protect-pte-in-ptepmd_mkuffd_wp.patch
mm-hugetlb-let-vma_offset_start-to-return-start.patch
mm-hugetlb-dont-wait-for-migration-entry-during-follow-page.patch
mm-hugetlb-document-huge_pte_offset-usage.patch
mm-hugetlb-move-swap-entry-handling-into-vma-lock-when-faulted.patch
mm-hugetlb-make-userfaultfd_huge_must_wait-safe-to-pmd-unshare.patch
mm-hugetlb-make-hugetlb_follow_page_mask-safe-to-pmd-unshare.patch
mm-hugetlb-make-follow_hugetlb_page-safe-to-pmd-unshare.patch
mm-hugetlb-make-walk_hugetlb_range-safe-to-pmd-unshare.patch
mm-hugetlb-introduce-hugetlb_walk.patch
