linux-kernel - Re: [PATCH 0/3] mm/gup: fixups for hugetlb gup rework series

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Message-ID: <dfb0873f-3559-4979-94d1-39c4a7a4ca3c@arm.com>
Date: Wed, 3 Apr 2024 12:06:28 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: peterx@...hat.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: Huacai Chen <chenhuacai@...nel.org>, David Hildenbrand
 <david@...hat.com>, Jason Gunthorpe <jgg@...dia.com>,
 Nathan Chancellor <nathan@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Matthew Wilcox <willy@...radead.org>, WANG Xuerui <kernel@...0n.name>,
 loongarch@...ts.linux.dev
Subject: Re: [PATCH 0/3] mm/gup: fixups for hugetlb gup rework series

On 03/04/2024 02:32, peterx@...hat.com wrote:
> From: Peter Xu <peterx@...hat.com>
> 
> Hi,
> 
> This is a small patchset that will fix two known issues that got reported
> today on the previous hugetlb unification series on slow gup [1].
> 
> The first issue was reported by Ryan Roberts [2] on a test failure over
> gup_longterm.  Patch 1-2 should fix it.  Tested with 32MB hugepages on
> arm64 VM.
> 
> The second issue was reported by Nathan Chancellor [3] on a build issue
> over loongson's defconfig (loongson3_defconfig).  It can be easily
> reproduced with my own build setup [4], while patch 3 fixes it, and should
> hopefully fix similar archs where pud_pfn() is not defined even if
> pud_leaf() can return true.
> 
> For the 2nd issue, it's debatable whether it's an arch issue, because
> logically speaking pud_pfn() and pud_leaf() should either be both defined
> or both not.  But since the current fix will be the simplest and still safe
> (I at least checked loongarch doesn't support either pud dax or pud
> hugetlb), I think we can consider having this to unbreak the build first,
> assuming this could also happen to other archs.
> 
> One note is that the last 2 patches should be squashed into corresponding
> patch, while the 1st patch should be kept standalone.
> 
> Thanks,
> 
> [1] https://lore.kernel.org/r/20240327152332.950956-1-peterx@redhat.com
> [2] https://lore.kernel.org/r/adfdd89b-ee56-4758-836e-c66a0be7de25@arm.com
> [3] https://lore.kernel.org/r/ZgyKLLVZ4vN56uZE@x1n
> [4] https://gitlab.com/peterx/lkb-harness/-/blob/main/config.json?ref_type=heads#L32
> 
> Peter Xu (3):
>   mm: Allow anon exclusive check over hugetlb tail pages
>   fixup! mm/gup: handle huge pmd for follow_pmd_mask()
>   fixup! mm/arch: provide pud_pfn() fallback
> 
>  include/linux/page-flags.h |  8 +++++++-
>  include/linux/pgtable.h    |  6 +++++-
>  mm/gup.c                   |  3 ---
>  mm/internal.h              | 10 ----------
>  4 files changed, 12 insertions(+), 15 deletions(-)
> 

With these applied, gup_longterm is now passing for me on arm64. So for the series:

Tested-by: Ryan Roberts <ryan.roberts@....com>