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Commit e8569dd2 authored by Andreas Sandberg's avatar Andreas Sandberg Committed by Linus Torvalds
Browse files

mm/hugetlb.c: call MMU notifiers when copying a hugetlb page range 



When copy_hugetlb_page_range() is called to copy a range of hugetlb
mappings, the secondary MMUs are not notified if there is a protection
downgrade, which breaks COW semantics in KVM.

This patch adds the necessary MMU notifier calls.

Signed-off-by: default avatarAndreas Sandberg <andreas@sandberg.pp.se>
Acked-by: default avatarSteve Capper <steve.capper@linaro.org>
Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 549543df

mm/hugetlb.c

+16 −5
Original line number Diff line number Diff line
@@ -2346,17 +2346,27 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, 
	int cow;

	struct hstate *h = hstate_vma(vma);

	unsigned long sz = huge_page_size(h);

	unsigned long mmun_start;	/* For mmu_notifiers */

	unsigned long mmun_end;		/* For mmu_notifiers */

	int ret = 0;



	cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;



	mmun_start = vma->vm_start;

	mmun_end = vma->vm_end;

	if (cow)

		mmu_notifier_invalidate_range_start(src, mmun_start, mmun_end);



	for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) {

		spinlock_t *src_ptl, *dst_ptl;

		src_pte = huge_pte_offset(src, addr);

		if (!src_pte)

			continue;

		dst_pte = huge_pte_alloc(dst, addr, sz);

		if (!dst_pte)

			goto nomem;

		if (!dst_pte) {

			ret = -ENOMEM;

			break;

		}



		/* If the pagetables are shared don't copy or take references */

		if (dst_pte == src_pte)
@@ -2377,10 +2387,11 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, 
		spin_unlock(src_ptl);

		spin_unlock(dst_ptl);

	}

	return 0;



nomem:

	return -ENOMEM;

	if (cow)

		mmu_notifier_invalidate_range_end(src, mmun_start, mmun_end);



	return ret;

}



static int is_hugetlb_entry_migration(pte_t pte)