linux-kernel - Re: [PATCH v2 1/5] prctl: extend PR_SET_THP_DISABLE to optionally exclude VM

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Message-ID: <f1b0ee33-fa64-4802-a575-c843ec459b7b@lucifer.local>
Date: Thu, 31 Jul 2025 14:18:59 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Usama Arif <usamaarif642@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, david@...hat.com,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, corbet@....net,
        rppt@...nel.org, surenb@...gle.com, mhocko@...e.com,
        hannes@...xchg.org, baohua@...nel.org, shakeel.butt@...ux.dev,
        riel@...riel.com, ziy@...dia.com, laoar.shao@...il.com,
        dev.jain@....com, baolin.wang@...ux.alibaba.com, npache@...hat.com,
        Liam.Howlett@...cle.com, ryan.roberts@....com, vbabka@...e.cz,
        jannh@...gle.com, Arnd Bergmann <arnd@...db.de>, sj@...nel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kernel-team@...a.com, Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v2 1/5] prctl: extend PR_SET_THP_DISABLE to optionally
 exclude VM_HUGEPAGE

On Thu, Jul 31, 2025 at 02:12:44PM +0100, Usama Arif wrote:
>
>
> On 31/07/2025 13:40, Lorenzo Stoakes wrote:
> > On Thu, Jul 31, 2025 at 01:27:18PM +0100, Usama Arif wrote:
> > [snip]
> >> Acked-by: Usama Arif <usamaarif642@...il.com>
> >> Tested-by: Usama Arif <usamaarif642@...il.com>
> >> Cc: Jonathan Corbet <corbet@....net>
> >> Cc: Andrew Morton <akpm@...ux-foundation.org>
> >> Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> >> Cc: Zi Yan <ziy@...dia.com>
> >> Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
> >> Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> >> Cc: Nico Pache <npache@...hat.com>
> >> Cc: Ryan Roberts <ryan.roberts@....com>
> >> Cc: Dev Jain <dev.jain@....com>
> >> Cc: Barry Song <baohua@...nel.org>
> >> Cc: Vlastimil Babka <vbabka@...e.cz>
> >> Cc: Mike Rapoport <rppt@...nel.org>
> >> Cc: Suren Baghdasaryan <surenb@...gle.com>
> >> Cc: Michal Hocko <mhocko@...e.com>
> >> Cc: Usama Arif <usamaarif642@...il.com>
> >> Cc: SeongJae Park <sj@...nel.org>
> >> Cc: Jann Horn <jannh@...gle.com>
> >> Cc: Liam R. Howlett <Liam.Howlett@...cle.com>
> >> Cc: Yafang Shao <laoar.shao@...il.com>
> >> Cc: Matthew Wilcox <willy@...radead.org>
> >
> > You don't need to include these Cc's, Andrew will add them for you.
> >
> >> Signed-off-by: David Hildenbrand <david@...hat.com>
> >> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> >
> > Shouldn't this also be signed off by you? 2/5 and 3/5 has S-o-b for both
> > David and yourself?
> >
> > This is inconsistent at the very least.
> >
>
> Signed-off-by: Usama Arif <usamaarif642@...il.com>
>
> The Ccs were added by David, and I didn't want to remove them.

Let's not add this noise on respins please, it makes review harder. No
other patch in the series, including ones by David, do it.

>
> >>
> >> ---
> >>
> >
> > Nothing below the --- will be included in the patch, so we can drop the
> > below, it's just noise that people can find easily if needed.
> >
> >> At first, I thought of "why not simply relax PR_SET_THP_DISABLE", but I
> >> think there might be real use cases where we want to disable any THPs --
> >> in particular also around debugging THP-related problems, and
> >> "never" not meaning ... "never" anymore ever since we add MADV_COLLAPSE.
> >> PR_SET_THP_DISABLE will also block MADV_COLLAPSE, which can be very
> >> helpful for debugging purposes. Of course, I thought of having a
> >> system-wide config option to modify PR_SET_THP_DISABLE behavior, but
> >> I just don't like the semantics.
> >
> > [snip]
> >
> >>
> >> Signed-off-by: David Hildenbrand <david@...hat.com>
> >
> > This S-o-b is weird, it's in a comment essentially. Let's drop that too
> > please.
>
>
> Everything below --- was added by David I believe to provide further explanation that
> doesn't need to be included in the commit message, and I didn't want to remove it
> or his 2nd sign-off, as its discarded anyways. Its useful info that can just be
> ignored.

Yup I get that, you've posted this several times now, anybody who needs it can
find it. Please remove on future respins to save me having to page through
noise.

The S-o-b was actively confusing, and this whole block of noise hid the
fact you got the S-o-b wrong on this patch.

Thanks