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Commit 0b0ac117 authored by Mike Kravetz's avatar Mike Kravetz Committed by Greg Kroah-Hartman
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hugetlb: take PMD sharing into account when flushing tlb/caches 

commit dff11abe upstream.

When fixing an issue with PMD sharing and migration, it was discovered via
code inspection that other callers of huge_pmd_unshare potentially have an
issue with cache and tlb flushing.

Use the routine adjust_range_if_pmd_sharing_possible() to calculate worst
case ranges for mmu notifiers.  Ensure that this range is flushed if
huge_pmd_unshare succeeds and unmaps a PUD_SUZE area.

Link: http://lkml.kernel.org/r/20180823205917.16297-3-mike.kravetz@oracle.com


Signed-off-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2387ff2f

mm/hugetlb.c

+43 −10
Original line number Diff line number Diff line
@@ -3384,8 +3384,8 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, 
	struct page *page;

	struct hstate *h = hstate_vma(vma);

	unsigned long sz = huge_page_size(h);

	const unsigned long mmun_start = start;	/* For mmu_notifiers */

	const unsigned long mmun_end   = end;	/* For mmu_notifiers */

	unsigned long mmun_start = start;	/* For mmu_notifiers */

	unsigned long mmun_end   = end;		/* For mmu_notifiers */

	bool force_flush = false;



	WARN_ON(!is_vm_hugetlb_page(vma));
@@ -3398,6 +3398,11 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, 
	 */

	tlb_remove_check_page_size_change(tlb, sz);

	tlb_start_vma(tlb, vma);



	/*

	 * If sharing possible, alert mmu notifiers of worst case.

	 */

	adjust_range_if_pmd_sharing_possible(vma, &mmun_start, &mmun_end);

	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);

	address = start;

	for (; address < end; address += sz) {
@@ -3508,12 +3513,23 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start, 
{

	struct mm_struct *mm;

	struct mmu_gather tlb;

	unsigned long tlb_start = start;

	unsigned long tlb_end = end;



	/*

	 * If shared PMDs were possibly used within this vma range, adjust

	 * start/end for worst case tlb flushing.

	 * Note that we can not be sure if PMDs are shared until we try to

	 * unmap pages.  However, we want to make sure TLB flushing covers

	 * the largest possible range.

	 */

	adjust_range_if_pmd_sharing_possible(vma, &tlb_start, &tlb_end);



	mm = vma->vm_mm;



	tlb_gather_mmu(&tlb, mm, start, end);

	tlb_gather_mmu(&tlb, mm, tlb_start, tlb_end);

	__unmap_hugepage_range(&tlb, vma, start, end, ref_page);

	tlb_finish_mmu(&tlb, start, end);

	tlb_finish_mmu(&tlb, tlb_start, tlb_end);

}



/*
@@ -4408,11 +4424,21 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, 
	pte_t pte;

	struct hstate *h = hstate_vma(vma);

	unsigned long pages = 0;

	unsigned long f_start = start;

	unsigned long f_end = end;

	bool shared_pmd = false;



	/*

	 * In the case of shared PMDs, the area to flush could be beyond

	 * start/end.  Set f_start/f_end to cover the maximum possible

	 * range if PMD sharing is possible.

	 */

	adjust_range_if_pmd_sharing_possible(vma, &f_start, &f_end);



	BUG_ON(address >= end);

	flush_cache_range(vma, address, end);

	flush_cache_range(vma, f_start, f_end);



	mmu_notifier_invalidate_range_start(mm, start, end);

	mmu_notifier_invalidate_range_start(mm, f_start, f_end);

	i_mmap_lock_write(vma->vm_file->f_mapping);

	for (; address < end; address += huge_page_size(h)) {

		spinlock_t *ptl;
@@ -4423,6 +4449,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, 
		if (huge_pmd_unshare(mm, &address, ptep)) {

			pages++;

			spin_unlock(ptl);

			shared_pmd = true;

			continue;

		}

		pte = huge_ptep_get(ptep);
@@ -4458,12 +4485,18 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, 
	 * Must flush TLB before releasing i_mmap_rwsem: x86's huge_pmd_unshare

	 * may have cleared our pud entry and done put_page on the page table:

	 * once we release i_mmap_rwsem, another task can do the final put_page

	 * and that page table be reused and filled with junk.

	 * and that page table be reused and filled with junk.  If we actually

	 * did unshare a page of pmds, flush the range corresponding to the pud.

	 */

	if (shared_pmd) {

		flush_hugetlb_tlb_range(vma, f_start, f_end);

		mmu_notifier_invalidate_range(mm, f_start, f_end);

	} else {

		flush_hugetlb_tlb_range(vma, start, end);

		mmu_notifier_invalidate_range(mm, start, end);

	}

	i_mmap_unlock_write(vma->vm_file->f_mapping);

	mmu_notifier_invalidate_range_end(mm, start, end);

	mmu_notifier_invalidate_range_end(mm, f_start, f_end);



	return pages << h->order;

}