linux-kernel - Re: [PATCH v3 29/30] luo: allow preserving memfd

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Message-ID: <mafs0ecsmv1ce.fsf@kernel.org>
Date: Thu, 04 Sep 2025 14:39:13 +0200
From: Pratyush Yadav <pratyush@...nel.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: Pratyush Yadav <pratyush@...nel.org>,  Jason Gunthorpe <jgg@...dia.com>,
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Subject: Re: [PATCH v3 29/30] luo: allow preserving memfd

Hi Mike,

On Wed, Sep 03 2025, Mike Rapoport wrote:
> On Wed, Sep 03, 2025 at 04:17:15PM +0200, Pratyush Yadav wrote:
>> On Tue, Sep 02 2025, Mike Rapoport wrote:
>> >
>> > As for porting kho_preserve_vmalloc() to kho_array, I also feel that it
>> > would just make kho_preserve_vmalloc() more complex and I'd rather simplify
>> > it even more, e.g. with preallocating all the pages that preserve indices
>> > in advance.
[...]
>  
>> Beyond that, I think KHO array will actually make kho_preserve_vmalloc()
>> simpler since it won't have to deal with the linked list traversal
>> logic. It can just do ka_for_each() and just get all the pages.
>>
>> We can also convert the preservation bitmaps to use it so the linked list
>> logic is in one place, and others just build on top of it.
>
> I disagree. The boilerplate to initialize and iterate the kho_array will
> not make neither vmalloc nor bitmaps preservation simpler IMO.

I have done 80% of the work on this already, so let's do this: I will do
the rest of the 20% and publish the patches. Then you and Jason can have
a look and if you still think it's not worth it, I am fine shelving it
for now and revisiting later when there might be a stronger case.

>
> And for bitmaps Pasha and Jason M. are anyway working on a different data
> structure already, so if their proposal moves forward converting bitmap
> preservation to anything would be a wasted effort.

-- 
Regards,
Pratyush Yadav