The patch titled
Subject: mm/hugetlb: take src_mm->write_protect_seq in copy_hugetlb_page_range()
has been added to the -mm tree. Its filename is
mm-hugetlb-take-src_mm-write_protect_seq-in-copy_hugetlb_page_range.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-take-src_mm-write_protect_seq-in-copy_hugetlb_page_range.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-take-src_mm-write_protect_seq-in-copy_hugetlb_page_range.patch
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/hugetlb: take src_mm->write_protect_seq in copy_hugetlb_page_range()
Let's do it just like copy_page_range(), taking the seqlock and making
sure the mmap_lock is held in write mode.
This allows for add a VM_BUG_ON to page_needs_cow_for_dma() and properly
synchronizes cocnurrent fork() with GUP-fast of hugetlb pages, which will
be relevant for further changes.
Link: https://lkml.kernel.org/r/20220329160440.193848-3-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Don Dutile <ddutile@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Liang Zhang <zhangliang5@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Nadav Amit <namit@xxxxxxxxxx>
Cc: Oded Gabbay <oded.gabbay@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Pedro Demarchi Gomes <pedrodemargomes@xxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 4 ++++
mm/hugetlb.c | 8 ++++++--
2 files changed, 10 insertions(+), 2 deletions(-)
--- a/include/linux/mm.h~mm-hugetlb-take-src_mm-write_protect_seq-in-copy_hugetlb_page_range
+++ a/include/linux/mm.h
@@ -1576,6 +1576,8 @@ static inline bool page_maybe_dma_pinned
/*
* This should most likely only be called during fork() to see whether we
* should break the cow immediately for a page on the src mm.
+ *
+ * The caller has to hold the PT lock and the vma->vm_mm->->write_protect_seq.
*/
static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
struct page *page)
@@ -1583,6 +1585,8 @@ static inline bool page_needs_cow_for_dm
if (!is_cow_mapping(vma->vm_flags))
return false;
+ VM_BUG_ON(!(raw_read_seqcount(&vma->vm_mm->write_protect_seq) & 1));
+
if (!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags))
return false;
--- a/mm/hugetlb.c~mm-hugetlb-take-src_mm-write_protect_seq-in-copy_hugetlb_page_range
+++ a/mm/hugetlb.c
@@ -4717,6 +4717,8 @@ int copy_hugetlb_page_range(struct mm_st
vma->vm_start,
vma->vm_end);
mmu_notifier_invalidate_range_start(&range);
+ mmap_assert_write_locked(src);
+ raw_write_seqcount_begin(&src->write_protect_seq);
} else {
/*
* For shared mappings i_mmap_rwsem must be held to call
@@ -4849,10 +4851,12 @@ again:
spin_unlock(dst_ptl);
}
- if (cow)
+ if (cow) {
+ raw_write_seqcount_end(&src->write_protect_seq);
mmu_notifier_invalidate_range_end(&range);
- else
+ } else {
i_mmap_unlock_read(mapping);
+ }
return ret;
}
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-rmap-fix-missing-swap_free-in-try_to_unmap-after-arch_unmap_one-failed.patch
mm-hugetlb-take-src_mm-write_protect_seq-in-copy_hugetlb_page_range.patch
mm-memory-slightly-simplify-copy_present_pte.patch
mm-rmap-split-page_dup_rmap-into-page_dup_file_rmap-and-page_try_dup_anon_rmap.patch
mm-rmap-convert-rmap-flags-to-a-proper-distinct-rmap_t-type.patch
mm-rmap-remove-do_page_add_anon_rmap.patch
mm-rmap-pass-rmap-flags-to-hugepage_add_anon_rmap.patch
mm-rmap-drop-compound-parameter-from-page_add_new_anon_rmap.patch
mm-rmap-use-page_move_anon_rmap-when-reusing-a-mapped-pageanon-page-exclusively.patch
mm-huge_memory-remove-outdated-vm_warn_on_once_page-from-unmap_page.patch
mm-page-flags-reuse-pg_mappedtodisk-as-pg_anon_exclusive-for-pageanon-pages.patch
mm-remember-exclusively-mapped-anonymous-pages-with-pg_anon_exclusive.patch
mm-gup-disallow-follow_pagefoll_pin.patch
mm-support-gup-triggered-unsharing-of-anonymous-pages.patch
mm-gup-trigger-fault_flag_unshare-when-r-o-pinning-a-possibly-shared-anonymous-page.patch
mm-gup-sanity-check-with-config_debug_vm-that-anonymous-pages-are-exclusive-when-unpinning.patch
mm-swap-remember-pg_anon_exclusive-via-a-swp-pte-bit.patch
mm-debug_vm_pgtable-add-tests-for-__have_arch_pte_swp_exclusive.patch
x86-pgtable-support-__have_arch_pte_swp_exclusive.patch
arm64-pgtable-support-__have_arch_pte_swp_exclusive.patch
s390-pgtable-cleanup-description-of-swp-pte-layout.patch
s390-pgtable-support-__have_arch_pte_swp_exclusive.patch
powerpc-pgtable-remove-_page_bit_swap_type-for-book3s.patch
powerpc-pgtable-support-__have_arch_pte_swp_exclusive-for-book3s.patch
