at 12:16 AM, Nicholas Piggin <npiggin@xxxxxxxxx> wrote:
> This reverts commit 4647706ebeee6e50f7b9f922b095f4ec94d581c3.
>
> Patch 99baac21e4585 ("mm: fix MADV_[FREE|DONTNEED] TLB flush miss
> problem") provides a superset of the TLB flush coverage of this
> commit, and even includes in the changelog "this patch supersedes
> 'mm: Always flush VMA ranges affected by zap_page_range v2'".
>
> Reverting this avoids double flushing the TLB range, and the less
> efficient flush_tlb_range() call (the mmu_gather API is more precise
> about what ranges it invalidates).
>
> Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> ---
> mm/memory.c | 14 +-------------
> 1 file changed, 1 insertion(+), 13 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 7206a634270b..9d472e00fc2d 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1603,20 +1603,8 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
> tlb_gather_mmu(&tlb, mm, start, end);
> update_hiwater_rss(mm);
> mmu_notifier_invalidate_range_start(mm, start, end);
> - for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
> + for ( ; vma && vma->vm_start < end; vma = vma->vm_next)
> unmap_single_vma(&tlb, vma, start, end, NULL);
> -
> - /*
> - * zap_page_range does not specify whether mmap_sem should be
> - * held for read or write. That allows parallel zap_page_range
> - * operations to unmap a PTE and defer a flush meaning that
> - * this call observes pte_none and fails to flush the TLB.
> - * Rather than adding a complex API, ensure that no stale
> - * TLB entries exist when this call returns.
> - */
> - flush_tlb_range(vma, start, end);
> - }
> -
> mmu_notifier_invalidate_range_end(mm, start, end);
> tlb_finish_mmu(&tlb, start, end);
> }
Yes, this was in my “to check when I have time” todo list, especially since
the flush was from start to end, not even vma->vm_start to vma->vm_end.
The revert seems correct.
Reviewed-by: Nadav Amit <namit@xxxxxxxxxx>
