+ mm-hugetlb-make-page_vma_mapped_walk-safe-to-pmd-unshare.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/hugetlb: make page_vma_mapped_walk() safe to pmd unshare
has been added to the -mm mm-unstable branch.  Its filename is
     mm-hugetlb-make-page_vma_mapped_walk-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-page_vma_mapped_walk-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@redhat.com>
Subject: mm/hugetlb: make page_vma_mapped_walk() safe to pmd unshare
Date: Tue, 29 Nov 2022 14:35:25 -0500

Since page_vma_mapped_walk() 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/20221129193526.3588187-10-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/rmap.h |    4 ++++
 mm/page_vma_mapped.c |    5 ++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

--- a/include/linux/rmap.h~mm-hugetlb-make-page_vma_mapped_walk-safe-to-pmd-unshare
+++ a/include/linux/rmap.h
@@ -13,6 +13,7 @@
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
 #include <linux/memremap.h>
+#include <linux/hugetlb.h>
 
 /*
  * The anon_vma heads a list of private "related" vmas, to scan if
@@ -408,6 +409,9 @@ static inline void page_vma_mapped_walk_
 		pte_unmap(pvmw->pte);
 	if (pvmw->ptl)
 		spin_unlock(pvmw->ptl);
+	/* This needs to be after unlock of the spinlock */
+	if (is_vm_hugetlb_page(pvmw->vma))
+		hugetlb_vma_unlock_read(pvmw->vma);
 }
 
 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
--- a/mm/page_vma_mapped.c~mm-hugetlb-make-page_vma_mapped_walk-safe-to-pmd-unshare
+++ a/mm/page_vma_mapped.c
@@ -169,10 +169,13 @@ bool page_vma_mapped_walk(struct page_vm
 		if (pvmw->pte)
 			return not_found(pvmw);
 
+		hugetlb_vma_lock_read(vma);
 		/* when pud is not present, pte will be NULL */
 		pvmw->pte = huge_pte_offset(mm, pvmw->address, size);
-		if (!pvmw->pte)
+		if (!pvmw->pte) {
+			hugetlb_vma_unlock_read(vma);
 			return false;
+		}
 
 		pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte);
 		if (!check_pte(pvmw))
_

Patches currently in -mm which might be from peterx@redhat.com 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