The patch titled
Subject: mm/hugetlb: make follow_hugetlb_page() safe to pmd unshare
has been added to the -mm mm-unstable branch. Its filename is
mm-hugetlb-make-follow_hugetlb_page-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-follow_hugetlb_page-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 follow_hugetlb_page() safe to pmd unshare
Date: Tue, 29 Nov 2022 14:35:23 -0500
Since follow_hugetlb_page() 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/20221129193526.3588187-8-peterx@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: James Houghton <jthoughton@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@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 | 7 +++++++
1 file changed, 7 insertions(+)
--- a/mm/hugetlb.c~mm-hugetlb-make-follow_hugetlb_page-safe-to-pmd-unshare
+++ a/mm/hugetlb.c
@@ -6290,6 +6290,7 @@ long follow_hugetlb_page(struct mm_struc
break;
}
+ hugetlb_vma_lock_read(vma);
/*
* Some archs (sparc64, sh*) have multiple pte_ts to
* each hugepage. We have to make sure we get the
@@ -6314,6 +6315,7 @@ long follow_hugetlb_page(struct mm_struc
!hugetlbfs_pagecache_present(h, vma, vaddr)) {
if (pte)
spin_unlock(ptl);
+ hugetlb_vma_unlock_read(vma);
remainder = 0;
break;
}
@@ -6335,6 +6337,8 @@ long follow_hugetlb_page(struct mm_struc
if (pte)
spin_unlock(ptl);
+ hugetlb_vma_unlock_read(vma);
+
if (flags & FOLL_WRITE)
fault_flags |= FAULT_FLAG_WRITE;
else if (unshare)
@@ -6394,6 +6398,7 @@ long follow_hugetlb_page(struct mm_struc
remainder -= pages_per_huge_page(h);
i += pages_per_huge_page(h);
spin_unlock(ptl);
+ hugetlb_vma_unlock_read(vma);
continue;
}
@@ -6421,6 +6426,7 @@ long follow_hugetlb_page(struct mm_struc
if (WARN_ON_ONCE(!try_grab_folio(pages[i], refs,
flags))) {
spin_unlock(ptl);
+ hugetlb_vma_unlock_read(vma);
remainder = 0;
err = -ENOMEM;
break;
@@ -6432,6 +6438,7 @@ long follow_hugetlb_page(struct mm_struc
i += refs;
spin_unlock(ptl);
+ hugetlb_vma_unlock_read(vma);
}
*nr_pages = remainder;
/*
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-migrate-fix-read-only-page-got-writable-when-recover-pte.patch
mm-always-compile-in-pte-markers.patch
mm-use-pte-markers-for-swap-errors.patch
mm-uffd-sanity-check-write-bit-for-uffd-wp-protected-ptes.patch
selftests-vm-use-memfd-for-hugepage-mmap-test.patch
mm-thp-re-apply-mkdirty-for-small-pages-after-split.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-make-page_vma_mapped_walk-safe-to-pmd-unshare.patch
mm-hugetlb-introduce-hugetlb_walk.patch
