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Mon, 30 Mar 2026 12:32:42 -0700 (PDT) MIME-Version: 1.0 References: <20260327033335.696621-1-pasha.tatashin@soleen.com> <20260327033335.696621-4-pasha.tatashin@soleen.com> In-Reply-To: From: Pasha Tatashin Date: Mon, 30 Mar 2026 15:32:05 -0400 X-Gm-Features: AQROBzAxVsQpca_B-s_NGbRebxXDIv48wSsMEMtKeJdaMcDdS4ixD-aE9zr90Ig Message-ID: Subject: Re: [PATCH v3 03/10] liveupdate: Protect file handler list with rwsem To: Samiullah Khawaja Cc: rppt@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, dmatlack@google.com, pratyush@kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: A6B961C0003 X-Stat-Signature: gwnmj7rghc9qs1uiexk6r1f3g5fj3wic X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1774899164-685972 X-HE-Meta: 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 JGTIEWpE MUPUW5UOHe/j+SHDQ0k3Rldy+CsXDNQJTPk2rkNQmZYDVJEhqJv17NCYeg8S+zae4V57osP8l2XxEx2ckPVJtDsPFxToIJvE0IlvEVgp4hiLfFzVr5Djcv71vBYLxM2MvgVD5VDjEz2gXAalXbwCYMkSd/joKCOWShdvvGEaJA5hmcrxfbqEP3Xud1xKMHmzE3DkXcE8YyQ38CogFnwsc7Lid+oy9UelzcOljD62IwMIyu/Y= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > >Because liveupdate file handlers will no longer hold a module reference > >when registered, we must ensure that the access to the handler list is > >protected against concurrent module unloading. > > Nit: Here we make an assumption that the file (and flb) handler > lifecycle is bound with the module lifecycle. It is a fair assumption, > but maybe this can be documented somewhere? That is true, we can certainly add this to Doc. comment. This could be done as a follow-up change if needed. > >+ up_read(&luo_register_rwlock); > > We took the read lock here when running can_preserve, but then we use > the fh without taking the lock later before calling file_preserve. This > is safe since the module reference is taken and fh will not go away > (based on the assumption I mentioned above). Maybe add a comment here > that documents this assumption. Sure, if I respin this series, I will add a comment; otherwise, it will be a follow-up change along with updating the documentation comment as you suggested above. Thanks, Pasha