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SubjectRe: [v11 PATCH 3/3] mm: unmap VM_PFNMAP mappings with optimized path
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On 9/19/18 7:03 PM, Yang Shi wrote:
> When unmapping VM_PFNMAP mappings, vm flags need to be updated. Since
> the vmas have been detached, so it sounds safe to update vm flags with
> read mmap_sem.
>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Reviewed-by: Matthew Wilcox <willy@infradead.org>
> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
> ---
> mm/mmap.c | 9 ---------
> 1 file changed, 9 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 490340e..847a17d 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2771,15 +2771,6 @@ static int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
> munlock_vma_pages_all(tmp);
> }
>
> - /*
> - * Unmapping vmas, which have VM_HUGETLB or VM_PFNMAP,

Ah, the comment should have been already updated with the previous
patch. But nevermind as that all goes away.

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> - * need get done with write mmap_sem held since they may
> - * update vm_flags.
> - */
> - if (downgrade &&
> - (tmp->vm_flags & VM_PFNMAP))
> - downgrade = false;
> -
> tmp = tmp->vm_next;
> }
> }
>

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