Re: [PATCH] mm/thp: fix call to mmu_notifier in set_pmd_migration_entry()

[Michal Hocko]

On Fri 12-10-18 12:09:53, jglisse@xxxxxxxxxx wrote:
> From: Jérôme Glisse <jglisse@xxxxxxxxxx>
> 
> Inside set_pmd_migration_entry() we are holding page table locks and
> thus we can not sleep so we can not call invalidate_range_start/end()
> 
> So remove call to mmu_notifier_invalidate_range_start/end() and add
> call to mmu_notifier_invalidate_range(). Note that we are already
> calling mmu_notifier_invalidate_range_start/end() inside the function
> calling set_pmd_migration_entry() (see try_to_unmap_one()).
> 
> Signed-off-by: Jérôme Glisse <jglisse@xxxxxxxxxx>
> Reported-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: David Nellans <dnellans@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>

Is this worth backporting to stable trees?

The patch looks good to me
Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  mm/huge_memory.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 533f9b00147d..93cb80fe12cb 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2885,9 +2885,6 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
>  	if (!(pvmw->pmd && !pvmw->pte))
>  		return;
>  
> -	mmu_notifier_invalidate_range_start(mm, address,
> -			address + HPAGE_PMD_SIZE);
> -
>  	flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
>  	pmdval = *pvmw->pmd;
>  	pmdp_invalidate(vma, address, pvmw->pmd);
> @@ -2898,11 +2895,9 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
>  	if (pmd_soft_dirty(pmdval))
>  		pmdswp = pmd_swp_mksoft_dirty(pmdswp);
>  	set_pmd_at(mm, address, pvmw->pmd, pmdswp);
> +	mmu_notifier_invalidate_range(mm, address, address + HPAGE_PMD_SIZE);
>  	page_remove_rmap(page, true);
>  	put_page(page);
> -
> -	mmu_notifier_invalidate_range_end(mm, address,
> -			address + HPAGE_PMD_SIZE);
>  }
>  
>  void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
> -- 
> 2.17.2

-- 
Michal Hocko
SUSE Labs