linux-kernel - Re: [PATCH 1/4] mm: gup: add FOLL

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Message-ID: <20141009103559.GK4750@worktop.programming.kicks-ass.net>
Date:	Thu, 9 Oct 2014 12:35:59 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Andres Lagar-Cavilla <andreslc@...gle.com>,
	Gleb Natapov <gleb@...nel.org>,
	Radim Krcmar <rkrcmar@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	Jianyu Zhan <nasa4836@...il.com>,
	Paul Cassella <cassella@...y.com>,
	Hugh Dickins <hughd@...gle.com>,
	Peter Feiner <pfeiner@...gle.com>,
	"\\\"Dr. David Alan Gilbert\\\"" <dgilbert@...hat.com>
Subject: Re: [PATCH 1/4] mm: gup: add FOLL_TRIED

On Wed, Oct 01, 2014 at 10:56:34AM +0200, Andrea Arcangeli wrote:
> From: Andres Lagar-Cavilla <andreslc@...gle.com>

This needs a changelog....

> Reviewed-by: Radim Krčmář <rkrcmar@...hat.com>
> Signed-off-by: Andres Lagar-Cavilla <andreslc@...gle.com>
> Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
> ---
>  include/linux/mm.h | 1 +
>  mm/gup.c           | 4 ++++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 8981cc8..0f4196a 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1985,6 +1985,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
>  #define FOLL_HWPOISON	0x100	/* check page is hwpoisoned */
>  #define FOLL_NUMA	0x200	/* force NUMA hinting page fault */
>  #define FOLL_MIGRATION	0x400	/* wait for page to replace migration entry */
> +#define FOLL_TRIED	0x800	/* a retry, previous pass started an IO */
>  
>  typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
>  			void *data);
> diff --git a/mm/gup.c b/mm/gup.c
> index 91d044b..af7ea3e 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -281,6 +281,10 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
>  		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
>  	if (*flags & FOLL_NOWAIT)
>  		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
> +	if (*flags & FOLL_TRIED) {
> +		VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
> +		fault_flags |= FAULT_FLAG_TRIED;
> +	}
>  
>  	ret = handle_mm_fault(mm, vma, address, fault_flags);
>  	if (ret & VM_FAULT_ERROR) {
--
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