linux-kernel - Re: [PATCH v3 1/2] kho: add support for preserving vmalloc allocations

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Message-ID: <aMl3C-jSa1_TBv0K@kernel.org>
Date: Tue, 16 Sep 2025 17:41:15 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Pratyush Yadav <pratyush@...nel.org>
Cc: Pratyush Yadav <me@...avpratyush.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Graf <graf@...zon.com>, Baoquan He <bhe@...hat.com>,
	Changyuan Lyu <changyuanl@...gle.com>, Chris Li <chrisl@...nel.org>,
	Jason Gunthorpe <jgg@...dia.com>,
	Pasha Tatashin <pasha.tatashin@...een.com>,
	kexec@...ts.infradead.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] kho: add support for preserving vmalloc
 allocations

On Tue, Sep 16, 2025 at 02:48:55PM +0200, Pratyush Yadav wrote:
> On Mon, Sep 15 2025, Mike Rapoport wrote:
> 
> > On Tue, Sep 09, 2025 at 04:33:27PM +0200, Pratyush Yadav wrote:
> >> Hi Mike,
> >> 
> >> Also, I am not a fan of using kho_restore_page() directly. I think the
> >> vmalloc preservation is a layer above core KHO, and it should use the
> >> public KHO APIs. It really doesn't need to poke into internal APIs. If
> >> any of the public APIs are insufficient, we should add new ones.
> >> 
> >> I don't suppose I'd insist on it, but something to consider since you
> >> are likely going to do another revision anyway.
> >
> > I think vmalloc is as basic as folio. At some point we probably converge to 
> > kho_preserve(void *) that will choose the right internal handler. like
> > folio, vmalloc, kmalloc etc.
> 
> Sure, but do you need to use the internal APIs? Because doing this way
> would miss some improvements for the public APIs. See my patch for
> adding more sanity checking to kho_restore_folio() for example:
> https://lore.kernel.org/linux-mm/20250910153443.95049-1-pratyush@kernel.org/
> 
> vmalloc preservation would miss this improvement since it uses the
> internal API, even though it will clearly benefit from it.

The core restore API is kho_restore_page() and the improvements should land
there, IMO.

Then whatever uses that core API will benefit from them.

-- 
Sincerely yours,
Mike.