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mm/hugetlb: take src_mm->write_protect_seq in copy_hugetlb_page_range()

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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 concurrent fork() with GUP-fast of hugetlb pages, which will
be relevant for further changes.

Link: https://lkml.kernel.org/r/20220428083441.37290-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Oded Gabbay <oded.gabbay@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2022-05-09 18:20:42 -07:00 committed by akpm
parent 322842ea3c
commit 623a1ddfeb
2 changed files with 10 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
include/linux/mm.h
View file

@ -1576,6 +1576,8 @@ static inline bool page_maybe_dma_pinned(struct page *page)
/*
* 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_dma(struct vm_area_struct *vma,
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;

8
mm/hugetlb.c
View file

@ -4735,6 +4735,8 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
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
@ -4867,10 +4869,12 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
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;
}