linux-kernel - Re: [PATCH v4 1/3] mm: pagewalk: simplify hugepage boundary

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Message-ID: <aXyJInpe7WmGaEmP@chandna.localdomain>
Date: Fri, 30 Jan 2026 16:04:10 +0530
From: Sahil Chandna <chandna.sahil@...il.com>
To: akpm@...ux-foundation.org, david@...hat.com, lorenzo.stoakes@...cle.com,
	mhocko@...e.com, vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com,
	hannes@...xchg.org, shakeel.butt@...ux.dev,
	zhengqi.arch@...edance.com, Liam.Howlett@...cle.com,
	weixugc@...gle.com, axelrasmussen@...gle.com, yuanchu@...gle.com,
	yosry.ahmed@...ux.dev, nphamcs@...il.com, chengming.zhou@...ux.dev,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, david@...nel.org,
	Sahil Chandna <chandna.sahil@...il.com>,
	Matthew Wilcox <willy@...radead.org>,
	David Laight <david.laight.linux@...il.com>
Subject: Re: [PATCH v4 1/3] mm: pagewalk: simplify hugepage boundary

On Thu, Dec 25, 2025 at 10:01:06AM +0000, David Laight wrote:
>On Thu, 25 Dec 2025 10:32:46 +0100
>"David Hildenbrand (Red Hat)" <david@...nel.org> wrote:
>
>> On 12/24/25 19:06, Matthew Wilcox wrote:
>> > On Wed, Dec 24, 2025 at 02:08:29PM +0000, David Laight wrote:
>> >>>>> +++ b/mm/pagewalk.c
>> >>>>> @@ -312,8 +312,7 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
>> >>>>>    static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
>> >>>>>    				       unsigned long end)
>> >>>>>    {
>> >>>>> -	unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
>> >>>>> -	return boundary < end ? boundary : end;
>> >>>>> +	return min(ALIGN(addr, huge_page_size(h)), end);
>> >>>>>    }
>> >>>>
>> >>>> Please drop this patch from the mm-new branch, as it causes
>> >>>> 'run_vmtests.sh' to hang. Specifically, it leads to the system hanging
>> >>>> when executing hugepage-vmemmap test, because the program falls into an
>> >>>> infinite loop in walk_hugetlb_range() and cannot break out.
>> >>>
>> >>> Good catch! The problem is that ALIGN() returns addr itself when already
>> >>> aligned, causing the infinite loop ...
>> >>
>> >> Using ALIGN(addr + 1, huge_page_size(h)) would work.
>> >> Although it could be (addr + 1) & ~huge_page_mask(h) which is probably
>> >> the easiest to understand.
>> >> Some of the 'helper' macros don't really make the code easier to read.
>> >> (And that includes a lot of uses of min().)
>> >
>> > Or we could go back to my original suggestion.
>> >
>> > https://lore.kernel.org/linux-mm/aRyOWrARRlUCeEz6@casper.infradead.org/
>> >
>> > which was in v2:
>> >
>> > https://lore.kernel.org/linux-mm/f802959f58865371ba1b10081bced98e3784c5e4.1763796152.git.chandna.sahil@gmail.com/
>>
>> I'm starting to wonder whether we should just leave that code alone :)
>>
>
>Maybe 'we' should stop checkpatch (etc) suggesting min() in trivial
>cases. It doesn't really make the code better.
>
>	David

Thank you for feedback, I dropped this patch this has been resubmitted [1].
This next two patches in this series were also dropped due to error in this
patch. Requesting feedback, if I can re-submit the other 2 patches which use 
the "%pe" printk format specifier ?
Sharing reference to patches [2] and [3] below.
Thanks,
Sahil

[1] https://lore.kernel.org/all/39f4490a-d713-44a8-a1d7-3568b01b3dc2@kernel.org/
[2] https://lore.kernel.org/all/2c842a64fddeb0fe0cac087783aaedd97edc3191.1764312627.git.chandna.sahil@gmail.com/
[3] https://lore.kernel.org/all/6d729a60eb71baade3670e5bb609a068683af3eb.1764312627.git.chandna.sahil@gmail.com/