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Wed, 25 Mar 2026 13:33:59 -0700 (PDT) MIME-Version: 1.0 References: <20260325182026.467307-1-pasha.tatashin@soleen.com> <20260325182026.467307-2-pasha.tatashin@soleen.com> <2vxzikajacgc.fsf@kernel.org> In-Reply-To: <2vxzikajacgc.fsf@kernel.org> From: David Matlack Date: Wed, 25 Mar 2026 13:33:31 -0700 X-Gm-Features: AQROBzBIp18gRPLcKPfh3wjTKZUVHHVImeKDpRy0cS80NjooMtufSaZyOa4m9uM Message-ID: Subject: Re: [PATCH v3 1/2] liveupdate: prevent double management of files To: Pratyush Yadav Cc: Pasha Tatashin , linux-kselftest@vger.kernel.org, rppt@kernel.org, shuah@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, skhawaja@google.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 257284000E X-Stat-Signature: ydu7qp6q1u58uc4hxcef8z1fa18jr6tt X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1774470841-325471 X-HE-Meta: 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 sGyekiNW E/jnc+PONMHV3TWDgKnn1qYW1FiPKJxCRH07W945j5zI5jY2FwQYz48UZZ7/dqXuLwdRa7CjZF6o7q/quJEfxt+zeMxM0qdkr8UkeENP+CSXoDsJMMY6xqNJ/zHVwjrdg+UYRLmwu0exu0qgFQK2sjAtHDpKcpD/Y+pwRzIVTRYVFKikTRkCCVSVFd6Skm//+f49MkJytMEJ1uU5cl6bD9Z6k1Ts18xX65hipMuMG+QUg6nFwlsN1D3QF+ePTIqorMAWv Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 25, 2026 at 1:20=E2=80=AFPM Pratyush Yadav wrote: > For memfd and hugetlb at least, we serialize the _inode_ not the file. > The inode has the contents that we care to preserve. > > So if two FDs point to the same inode, this will break. You can do this > by first creating a memfd and then by opening "/proc/self/fd/". Then > you would be able to trigger the preservation twice, causing all sorts > of problems. Same on the retrieve side. > So unless I am missing something, I don't think this approach will work. > As much as I hate to suggest it, I think we need to move this check to > each caller so they can find out the object they need to serialize and > check if it already is. I think LUO can still enforce that the file is not preserved twice. HugeTLB and memfd's preserve() functions just need to also check that the associated inode has not already been preserved?