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

[Sahil Chandna]

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@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxx/
> > >
> > > which was in v2:
> > >
> > > https://lore.kernel.org/linux-mm/f802959f58865371ba1b10081bced98e3784c5e4.1763796152.git.chandna.sahil@xxxxxxxxx/
> >
> > 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@xxxxxxxxxx/
[2] https://lore.kernel.org/all/2c842a64fddeb0fe0cac087783aaedd97edc3191.1764312627.git.chandna.sahil@xxxxxxxxx/
[3] https://lore.kernel.org/all/6d729a60eb71baade3670e5bb609a068683af3eb.1764312627.git.chandna.sahil@xxxxxxxxx/