linux-kernel - Re: [PATCH v3 0/2] Allow gmap fault to retry

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Message-ID: <20160104170857.GA3702@redhat.com>
Date:	Mon, 4 Jan 2016 18:08:57 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Dominik Dingel <dingel@...ux.vnet.ibm.com>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	"Jason J. Herne" <jjherne@...ux.vnet.ibm.com>,
	linux-s390@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Eric B Munson <emunson@...mai.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Mel Gorman <mgorman@...e.de>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/2] Allow gmap fault to retry

On Mon, Jan 04, 2016 at 12:19:53PM +0100, Dominik Dingel wrote:
> Hello,
> 
> sorry for the delay since the last version.
> 
> During Jasons work with postcopy migration support for s390 a problem regarding
> gmap faults was discovered.
> 
> The gmap code will call fixup_user_fault which will end up always in
> handle_mm_fault. Till now we never cared about retries, but as the userfaultfd
> code kind of relies on it. this needs some fix.
> 
> This patchset does not take care of the futex code. I will now look closer at
> this.
> 
> Thanks,
>     Dominik
> 
> v2 -> v3:
> - In case of retrying check vma again
> - Do the accounting of major/minor faults once

Reviewed-by: Andrea Arcangeli <aarcange@...hat.com>


> 
> v1 -> v2:
> - Instread of passing the VM_FAULT_RETRY from fixup_user_fault we do retries
>   within fixup_user_fault, like get_user_pages_locked do.
> - gmap code will now take retry if fixup_user_fault drops the lock.
> 
> Dominik Dingel (2):
>   mm: bring in additional flag for fixup_user_fault to signal unlock
>   s390/mm: enable fixup_user_fault retrying
> 
>  arch/s390/mm/pgtable.c | 31 ++++++++++++++++++++++++++++---
>  include/linux/mm.h     |  5 +++--
>  kernel/futex.c         |  2 +-
>  mm/gup.c               | 30 +++++++++++++++++++++++++-----
>  4 files changed, 57 insertions(+), 11 deletions(-)
> 
> -- 
> 2.3.0
> 
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