linux-kernel - Re: [PATCH] Hugetlb pages should not be reserved by shmat() if SHM

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Date: Sun, 21 Jan 2024 14:32:07 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Prakash Sangappa <prakash.sangappa@...cle.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, muchun.song@...ux.dev,
 mike.kravetz@...cle.com
Subject: Re: [PATCH] Hugetlb pages should not be reserved by shmat() if
 SHM_NORESERVE

On Fri, 19 Jan 2024 17:17:52 -0800 Prakash Sangappa <prakash.sangappa@...cle.com> wrote:

> For shared memory of type SHM_HUGETLB, hugetlb pages are reserved in
> shmget() call. If SHM_NORESERVE flags is specified then the hugetlb
> pages are not reserved. However when the shared memory is attached
> with the shmat() call the hugetlb pages are getting reserved incorrectly
> for SHM_HUGETLB shared memory created with SHM_NORESERVE.
> 
> Ensure that the hugetlb pages are no reserved for SHM_HUGETLB shared
> memory in the shmat() call.

Thanks.

What are the userspace-visible effects of this change?

Based on that, is a -stable backport desirable?

And can we please identify a suitable Fixes: target for this?