linux-kernel - Re: [PATCH 2/2] liveupdate: kho: allocate metadata directly from the buddy allocator

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Message-ID: <20251024132155.GA760669@ziepe.ca>
Date: Fri, 24 Oct 2025 10:21:55 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Pasha Tatashin <pasha.tatashin@...een.com>
Cc: akpm@...ux-foundation.org, brauner@...nel.org, corbet@....net,
	graf@...zon.com, linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
	masahiroy@...nel.org, ojeda@...nel.org, pratyush@...nel.org,
	rdunlap@...radead.org, rppt@...nel.org, tj@...nel.org,
	jasonmiu@...gle.com, dmatlack@...gle.com, skhawaja@...gle.com
Subject: Re: [PATCH 2/2] liveupdate: kho: allocate metadata directly from the
 buddy allocator

On Wed, Oct 15, 2025 at 01:31:21AM -0400, Pasha Tatashin wrote:
> -	elm = kzalloc(sz, GFP_KERNEL);
> +	order = get_order(sz);
> +	elm = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
>  	if (!elm)
>  		return ERR_PTR(-ENOMEM);

Please add a function to allocate preservable non-scratch pages then
:\ I don't think we should be sprinkling __get_free_pages() all over
the place.

You can then add a cleanup.h for the new function and so on.

It should allocate frozen pages, accept a size_t and return a void *.

If this issue is only related to kfence then the new function could
have an if IS_ENABLED(KFENCE) and use slab when it is safe.

Jason