linux-kernel - Re: [PATCH 1/2] mm: fixup_userfault returns VM_FAULT

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Date:	Thu, 19 Nov 2015 02:14:40 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Dominik Dingel <dingel@...ux.vnet.ibm.com>
Cc:	linux-s390@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	Eric B Munson <emunson@...mai.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Mel Gorman <mgorman@...e.de>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	"Jason J. Herne" <jjherne@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: fixup_userfault returns VM_FAULT_RETRY if asked

On Thu, Nov 19, 2015 at 12:49:57AM +0100, Dominik Dingel wrote:
> When calling fixup_userfault with FAULT_FLAG_ALLOW_RETRY, fixup_userfault
> didn't care about VM_FAULT_RETRY and returned 0. If the VM_FAULT_RETRY flag is
> set we will return the complete result of handle_mm_fault.
> 
> Signed-off-by: Dominik Dingel <dingel@...ux.vnet.ibm.com>
> ---
>  mm/gup.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index deafa2c..2af3b31 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -609,6 +609,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
>  			return -EFAULT;
>  		BUG();
>  	}
> +	if (ret & VM_FAULT_RETRY)
> +		return ret;

Nope. fixup_user_fault() return errno, not VM_FAULT_* mask.

I guess it should be
		return -EBUSY;

>  	if (tsk) {
>  		if (ret & VM_FAULT_MAJOR)
>  			tsk->maj_flt++;
> -- 
> 2.3.9
> 

-- 
 Kirill A. Shutemov
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