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[34.127.79.33]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ed090a1475sm11919255ad.41.2026.11.04.14.32.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 14:32:20 -0800 (PST) Date: Wed, 4 Nov 2026 22:32:15 +0000 From: David Matlack To: Pratyush Yadav Cc: kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Alexander Graf , Andrew Morton , Baolin Wang , Christian Brauner , David Hildenbrand , Hugh Dickins , Jonathan Corbet , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Pasha Tatashin , Randy Dunlap , Samiullah Khawaja , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka Subject: Re: [PATCH v3 08/10] mm/shmem_luo: Allow preserving tmpfs files that are still linked Message-ID: References: <20261103010216.3447716-1-dmatlack@google.com> <20261103010216.3447716-9-dmatlack@google.com> <2vxza4nok0ji.fsf@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2vxza4nok0ji.fsf@kernel.org> On 2026-11-04 05:45 PM, Pratyush Yadav wrote: [...] > > + * Preserving a file requires it to be opened for reading, since the retrieved > > + * file can be read. It also requires permission to write to the file, since > > + * preserving it affects all of its users, as described below. But the file > > + * doesn't need to be opened for writing. For example, a binary that is being > > + * executed can be preserved through a read-only file descriptor. The owner of > > Why are you talking about preserving binaries being executed? Seems > oddly specific. I didn't know that was a use case we cared about. It's the reason the check looks at permission on the inode instead of requiring an fd opened for writing: a running binary can't be opened for writing (-ETXTBSY), so requiring a writable fd would make it impossible to preserve. Preserving binaries is a use case we care about, e.g. to carry over the binaries of services across a Live Update. I'll keep the comment shorter and more general in v4.