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b=IcWnR77vCDQ5A61TLKtCNAVCZB7jbpvXZ+8G6QaOMzO5QKTWK6akbiQRv3egGutQU /9hyKuUu1s57DZXH+BA+kg/WfrUiOCpQnbYohzuCW7iyfDgLLNrIr620fHGaONIh8a n57yTFoGWM57hiZ3Jq6VmiYQYMTTiZhqWoohDzNg= Date: Sun, 21 Jan 2024 14:32:07 -0800 From: Andrew Morton To: Prakash Sangappa Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, muchun.song@linux.dev, mike.kravetz@oracle.com Subject: Re: [PATCH] Hugetlb pages should not be reserved by shmat() if SHM_NORESERVE Message-Id: <20240121143207.299f0d3df52ac746224dacd8@linux-foundation.org> In-Reply-To: <1705713472-3537-1-git-send-email-prakash.sangappa@oracle.com> References: <1705713472-3537-1-git-send-email-prakash.sangappa@oracle.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 31A7A1A0004 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: cw6ka73k1fdffg7pkfz64fz7seisir5r X-HE-Tag: 1705876332-382418 X-HE-Meta: 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 ZZe5k7yl N4fvW2vcQ/kEqM9jvQmeCCep8djYQja2HOTlj8OItSaRJ2SQFRw+PnrjA2w7Tf12gAHckSPgT+dbPC4daAK4qDeHnv5ty+9EQ6ynBKfDQxofBS9nojDy5JHImjfmn2U2LzxKRwgbMwCqLqQ9TEblhbY9Zw+bVzElZCEy9XA1BWnLEnuUaJnCmFdUnb8BUHlW2mmHKoWRFnu2wipE2oYSt2VW0ndgaolMWZ/gVvXX1Imn1r5sFsesGA1KW2zhLqZ9xRyP0r4xYNmzXfEn/oOz5KEPTP0l08IZtYgGq4HhACLgzXHk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 19 Jan 2024 17:17:52 -0800 Prakash Sangappa 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?