Re: Page migration issue with UBIFS

On Tue, Mar 15, 2016 at 04:25:50PM +0100, Richard Weinberger wrote:

Kirill,

Am 15.03.2016 um 16:17 schrieb Kirill A. Shutemov:

quoted

On Tue, Mar 15, 2016 at 03:16:11PM +0100, Richard Weinberger wrote:

quoted

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?

Thanks for your quick response!

I also don't think that the root cause is CMA or migration but it seems
to be the messenger.

Can you confirm that UBIFS's assumptions are valid?
I'm trying to rule out possible issues and hunt down the root cause...

The assumption looks reasonable for me, but I am not confident enough to
"confirm" it.

-- 
 Kirill A. Shutemov

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