linux-kernel - Re: [RFC PATCH 1/4] mm: use current as mmu notifier's owner

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Message-ID: <2982b6f1-7c14-46ef-afb0-7951f7cdc2aa@redhat.com>
Date: Thu, 14 Aug 2025 20:45:43 +0300
From: Mika Penttilä <mpenttil@...hat.com>
To: Jason Gunthorpe <jgg@...dia.com>, Alistair Popple <apopple@...dia.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 David Hildenbrand <david@...hat.com>, Leon Romanovsky <leonro@...dia.com>,
 Balbir Singh <balbirs@...dia.com>
Subject: Re: [RFC PATCH 1/4] mm: use current as mmu notifier's owner


On 8/14/25 20:20, Jason Gunthorpe wrote:

> On Thu, Aug 14, 2025 at 08:00:01PM +0300, Mika Penttilä wrote:
>> as well as hmm test module with :
>>
>>          * Ignore invalidation callbacks for device private pages since
>>          * the invalidation is handled as part of the migration process.
>>          */
>>         if (range->event == MMU_NOTIFY_MIGRATE &&
>>             range->owner == dmirror->mdevice)
>>                 return true;
> If I recall this was about a very specific case where migration does a
> number of invalidations and some of the earlier ones are known to be
> redundant in this specific case. Redundant means it can be ignored
> without causing an inconsistency.
>
> Alistair would know, but I assumed this works OK because the above
> invalidation doesn't actually go on to free any pages but keeps them
> around until a later invalidation?
>
> This is nothing like what your case is talking about.

This one is actually pretty similar, MMU_NOTIFY_CLEAR is also fired in migration process
(split case) and invalidation handled part of the migration process.

But I have already a working version without any of that.

>
> Jason
>
--Mika