linux-kernel - Re: Page migration issue with UBIFS

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Date:	Tue, 15 Mar 2016 16:32:40 +0100
From:	Richard Weinberger <richard@....at>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	David Gstir <david@...ma-star.at>,
	Dave Chinner <david@...morbit.com>,
	Artem Bityutskiy <dedekind1@...il.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Alexander Kaplan <alex@...tthing.co>
Subject: Re: Page migration issue with UBIFS

Am 15.03.2016 um 16:17 schrieb Kirill A. Shutemov:
> On Tue, Mar 15, 2016 at 03:16:11PM +0100, Richard Weinberger wrote:
>> Hi!
>>
>> We're facing this issue from 2014 on UBIFS:
>> http://www.spinics.net/lists/linux-fsdevel/msg79941.html
>>
>> So sum up:
>> UBIFS does not allow pages directly marked as dirty. It want's everyone to do it via UBIFS's
>> ->wirte_end() and ->page_mkwirte() functions.
>> This assumption *seems* to be violated by CMA which migrates pages.
> 
> I don't thing the CMA/migration is the root cause.
> 
> How did we end up with writable and dirty pte, but not having
> ->page_mkwrite() called for the page?
> 
> Or if ->page_mkwrite() was called, why the page is not dirty?

BTW: UBIFS does not implement ->migratepage(), could this be a problem?

Thanks,
//richard