linux-kernel - Re: [PATCH] sparc64: fix hugetlb for sun4u

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Message-ID: <f358f3ce-1140-4dd1-a1b8-379563c5f050@redhat.com>
Date: Mon, 11 Aug 2025 10:25:03 +0200
From: David Hildenbrand <david@...hat.com>
To: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
 Anthony Yznaga <anthony.yznaga@...cle.com>, sparclinux@...r.kernel.org,
 davem@...emloft.net, andreas@...sler.com
Cc: linux-kernel@...r.kernel.org, agordeev@...ux.ibm.com, will@...nel.org,
 ryan.roberts@....com, osalvador@...e.de
Subject: Re: [PATCH] sparc64: fix hugetlb for sun4u

On 11.08.25 00:20, John Paul Adrian Glaubitz wrote:
> Hi,
> 
> On Sun, 2025-08-10 at 11:52 +0200, John Paul Adrian Glaubitz wrote:
>> On Sat, 2025-08-09 at 08:42 +0200, John Paul Adrian Glaubitz wrote:
>>> Let me know if you have more suggestions to test. I can also provide you with full
>>> access to this Netra 240 if you send me your public SSH key in a private mail.
>>
>> I have narrowed it down to a regression between v6.3 and v6.4 now.
>>
>> The bug can be reproduced with the sparc64_defconfig on a Sun Netra 240 by setting
>> CONFIG_TRANSPARENT_HUGEPAGE=y and CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS=y. When testing
>> on a modern systemd-based distribution, it's also necessary to enable CGroup support
>> as well as enable support for Sun partition tables with CONFIG_SUN_PARTITION=y.
>>
>> Then it should be a matter of bisecting the commits between v6.3 and v6.4.
>>
>> I will do that within the next days as I'm currently a bit busy with other stuff.
> 
> OK, it turns out it's reproducible on older kernels (but not as old as 4.19) as well.
> It's just much harder to trigger. I found a reproducer though and will try to find
> the problematic commit next.

ext4 support for large folios was added recently (6.16? not 100% sure).

But below can indicate some ext4 issue with large folios. 
(fault:filemap_fault mmap:ext4_file_mmap)

-- 
Cheers,

David / dhildenb