[PATCH v9 2/3] hugetlb: remove duplicate mmu notifications

Mike Kravetz
2022-11-11T23:26:58Z

The common hugetlb unmap routine __unmap_hugepage_range performs mmu
notification calls. However, in the case where __unmap_hugepage_range
is called via __unmap_hugepage_range_final, mmu notification calls are
performed earlier in other calling routines.

Remove mmu notification calls from __unmap_hugepage_range. Add
notification calls to the only other caller: unmap_hugepage_range.
unmap_hugepage_range is called for truncation and hole punch, so
change notification type from UNMAP to CLEAR as this is more appropriate.

Fixes: 90e7e7f5ef3f ("mm: enable MADV_DONTNEED for hugetlb mappings")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: Wei Chen <harperchen1110@gmail.com>
Cc: <stable@vger.kernel.org>
---
mm/hugetlb.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9d765364231e..205c67c6787a 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5074,7 +5074,6 @@ static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct
struct page *page;
struct hstate *h = hstate_vma(vma);
unsigned long sz = huge_page_size(h);
- struct mmu_notifier_range range;
unsigned long last_addr_mask;
bool force_flush = false;

@@ -5089,13 +5088,6 @@ static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct
tlb_change_page_size(tlb, sz);
tlb_start_vma(tlb, vma);

- /*
- * If sharing possible, alert mmu notifiers of worst case.
- */
- mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, mm, start,
- end);
- adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
- mmu_notifier_invalidate_range_start(&range);
last_addr_mask = hugetlb_mask_last_page(h);
address = start;
for (; address < end; address += sz) {
@@ -5180,7 +5172,6 @@ static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct
if (ref_page)
break;
}
- mmu_notifier_invalidate_range_end(&range);
tlb_end_vma(tlb, vma);

/*
@@ -5208,6 +5199,7 @@ void __unmap_hugepage_range_final(struct mmu_gather *tlb,
hugetlb_vma_lock_write(vma);
i_mmap_lock_write(vma->vm_file->f_mapping);

+ /* mmu notification performed in caller */
__unmap_hugepage_range(tlb, vma, start, end, ref_page, zap_flags);

/*
@@ -5227,10 +5219,18 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
unsigned long end, struct page *ref_page,
zap_flags_t zap_flags)
{
+ struct mmu_notifier_range range;
struct mmu_gather tlb;

+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
+ start, end);
+ adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
+ mmu_notifier_invalidate_range_start(&range);
tlb_gather_mmu(&tlb, vma->vm_mm);
+
__unmap_hugepage_range(&tlb, vma, start, end, ref_page, zap_flags);
+
+ mmu_notifier_invalidate_range_end(&range);
tlb_finish_mmu(&tlb);
}

--
2.37.3