linux-kernel - Re: mlock ulimits for SHM

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Message-ID: <aCs6C2vKbecx-boy@tiehlicka>
Date: Mon, 19 May 2025 16:02:51 +0200
From: Michal Hocko <mhocko@...e.com>
To: Bharat Agrawal <bharat.agrawal@...ys.com>
Cc: "hughd@...gle.com" <hughd@...gle.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"rientjes@...gle.com" <rientjes@...gle.com>,
	"zhangyiru3@...wei.com" <zhangyiru3@...wei.com>,
	"mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
	"liuzixian4@...wei.com" <liuzixian4@...wei.com>,
	"wuxu.wu@...wei.com" <wuxu.wu@...wei.com>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: mlock ulimits for SHM_HUGETLB

Hi,
On Mon 19-05-25 10:21:17, Bharat Agrawal wrote:
> Hi all,
> 
> Could anyone please help comment on the risks associated with an
> application throwing the "Using mlock ulimits for SHM_HUGETLB is
> deprecated" message on RHEL 8.9 with 4.18.0-513.18.1.el8_9.x86_64
> Linux kernel?

This is not RHEL specific behavior. The current Linus tree has the same
warning which has been added by 
: commit 2584e517320bd48dc8d20e38a2621a2dbe58fade
: Author: Ravikiran G Thirumalai <kiran@...lex86.org>
: Date:   Tue Mar 31 15:21:26 2009 -0700
: 
:     mm: reintroduce and deprecate rlimit based access for SHM_HUGETLB
: 
:     Allow non root users with sufficient mlock rlimits to be able to allocate
:     hugetlb backed shm for now.  Deprecate this though.  This is being
:     deprecated because the mlock based rlimit checks for SHM_HUGETLB is not
:     consistent with mmap based huge page allocations.
: 
:     Signed-off-by: Ravikiran Thirumalai <kiran@...lex86.org>
:     Reviewed-by: Mel Gorman <mel@....ul.ie>
:     Cc: William Lee Irwin III <wli@...omorphy.com>
:     Cc: Adam Litke <agl@...ibm.com>
:     Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
:     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

HTH
-- 
Michal Hocko
SUSE Labs