linux-kernel - Re: [RFC PATCH 2/4] mm: Change the interface for __tlb_remove

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Message-ID: <001901d1ba4a$514eccc0$f3ec6640$@alibaba-inc.com>
Date:	Mon, 30 May 2016 16:07:31 +0800
From:	"Hillf Danton" <hillf.zj@...baba-inc.com>
To:	"Aneesh Kumar" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [RFC PATCH 2/4] mm: Change the interface for __tlb_remove_page

> diff --git a/mm/memory.c b/mm/memory.c
> index 15322b73636b..a01db5bc756b 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -292,23 +292,24 @@ void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long e
>   *	handling the additional races in SMP caused by other CPUs caching valid
>   *	mappings in their TLBs. Returns the number of free page slots left.
>   *	When out of page slots we must call tlb_flush_mmu().
> + *returns true if the caller should flush.
>   */
> -int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
> +bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
>  {
>  	struct mmu_gather_batch *batch;
> 
>  	VM_BUG_ON(!tlb->end);
> 
>  	batch = tlb->active;
> -	batch->pages[batch->nr++] = page;
>  	if (batch->nr == batch->max) {
>  		if (!tlb_next_batch(tlb))
> -			return 0;
> +			return true;
>  		batch = tlb->active;
>  	}
>  	VM_BUG_ON_PAGE(batch->nr > batch->max, page);

Still needed?
> 
> -	return batch->max - batch->nr;
> +	batch->pages[batch->nr++] = page;
> +	return false;
>  }
> 
>  #endif /* HAVE_GENERIC_MMU_GATHER */
> @@ -1109,6 +1110,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
>  	pte_t *start_pte;
>  	pte_t *pte;
>  	swp_entry_t entry;
> +	struct page *pending_page = NULL;
> 
>  again:
>  	init_rss_vec(rss);
> @@ -1160,8 +1162,9 @@ again:
>  			page_remove_rmap(page, false);
>  			if (unlikely(page_mapcount(page) < 0))
>  				print_bad_pte(vma, addr, ptent, page);
> -			if (unlikely(!__tlb_remove_page(tlb, page))) {
> +			if (unlikely(__tlb_remove_page(tlb, page))) {
>  				force_flush = 1;
> +				pending_page = page;
>  				addr += PAGE_SIZE;
>  				break;
>  			}
> @@ -1202,7 +1205,12 @@ again:
>  	if (force_flush) {
>  		force_flush = 0;
>  		tlb_flush_mmu_free(tlb);
> -
> +		if (pending_page) {
> +			/* remove the page with new size */
> +			__tlb_adjust_range(tlb, tlb->addr);

Would you please specify why tlb->addr is used here?

thanks
Hillf 
> +			__tlb_remove_page(tlb, pending_page);
> +			pending_page = NULL;
> +		}
>  		if (addr != end)
>  			goto again;
>  	}
> --
> 2.7.4