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	Mon, 25 May 2026 07:16:23 +0000
Date: Mon, 25 May 2026 00:16:23 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Mike Rapoport <rppt@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH] block: partitions: replace __get_free_page() with
 kmalloc()
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References: <20260520-block-v1-1-6463dc2cf042@kernel.org>
 <ahPnX-CwVgK-9chp@infradead.org>
 <ahPxmSqT4Y4jcAbQ@kernel.org>
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On Mon, May 25, 2026 at 09:52:09AM +0300, Mike Rapoport wrote:
> On Sun, May 24, 2026 at 11:08:31PM -0700, Christoph Hellwig wrote:
> > On Wed, May 20, 2026 at 11:15:52AM +0300, Mike Rapoport (Microsoft) wrote:
> > > check_partition() allocates a buffer to use as backing buffer for
> > > seq_buf.
> > > 
> > > This buffer can be allocated with kmalloc() as there's nothing special
> > > about it to go directly to the page allocator.
> > > 
> > > Replace use of __get_free_page() with kmalloc() and free_page() with
> > > kfree().
> > 
> > So I heard various vague references that we should replace
> > __get_free_page with kmalloc, but nothing definitive.  Can you please
> > point to a good resource for that?
> 
> There was quite recent discussion when I posted patches that change
> __get_free_page to return void *:
> 
> https://lore.kernel.org/all/20251018093002.3660549-1-rppt@kernel.org/

This doesn't tell much more.

> And an old thread when Al posted similar patches:
> 
> https://lore.kernel.org/all/CA+55aFwp4iy4rtX2gE2WjBGFL=NxMVnoFeHqYa2j1dYOMMGqxg@mail.gmail.com/T/#u<S-Del>

This does, but it still fails to explain why kmalloc performs just as
well as __get_free_page(s) these days.

And such an explanation or link to it should go into every patch doing
this switch.