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Tue, 20 Oct 2026 03:20:25 -0700 (PDT) From: Daehyeon Ko <4ncienth@gmail.com> To: david@kernel.org Cc: muchun.song@linux.dev, osalvador@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] hugetlb: retry private VMA locking when unmapping folios Date: Tue, 20 Oct 2026 19:20:12 +0900 Message-ID: <20261020102012.1775940-1-4ncienth@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <23623534-a163-4ffa-8538-b5aff7daecaf@kernel.org> References: <20261015170551.2656546-1-4ncienth@gmail.com> <23623534-a163-4ffa-8538-b5aff7daecaf@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 42BE7A0009 X-Rspam-User: X-Stat-Signature: rda5jwhdct5m9x4ajpppinye4cb36omy X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam03 X-HE-Tag: 1792491631-294098 X-HE-Meta: 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 UDvucfEU 0W4RaNvCgRZxBqV3vwbIrjBniO5IjAdS5gOk0z1wtJLcivTYuRs5eFGdlGwp9YsFWIHUsD29LDD3TXr23n0PJFDsXXtWOY44XFYw1ZLfm5oJKxnQ3YMgZtm/RNd0szYuuo5OCJDUvOUAo5/Lz+Rx5RcuT+3zFfju9Q4Rjvi32BET+9uKw8/mC+jVdFnTJ6E5myQjsdennfnsi9LyFV6FEjs/G7iR2F31M/GJSY8Orc5BV0aHp4fjy7g1n+ZWnKsv9ag1t0nzykX13s7mjVrPE76F1QKA7I2+0m3hBR5vra5x8MFRzv8V0UO/BON0iDuqPYyc7AW8v1iFaVn/1a5MC8eKaLCtLQq7P5T57B+oyHMk8QyEAaDIKbj8q995amYRtgh2nd6HsNoP+tvTwn2uDB1scFA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Hi David, Yes, that makes sense. The per-index fault mutex excludes concurrent faults for the folio being removed, while i_mmap_rwsem keeps the VMA in the mapping tree and excludes concurrent page-table teardown. So the private resv_map lock is not needed in this path. I tested the exact diff from your message on v7.3-rc5 with KASAN+LOCKDEP. My unprivileged mprotect()/hole-punch reproducer completed 1,000 rounds (64,000 hole punches) with no KASAN, lockdep, unexpected warning, oops, or panic. Please consider my patch superseded by Josef's fix. One small typo in the quoted comment: "i_mmap_rwsem everybody" appears to be missing "excludes". The quoted commit also predates the current linux-next policy change: `Assisted-by` is no longer a recognized trailer. `generated-content.rst` asks that tool-assisted discovery be stated in the changelog prose instead. Tested-by: Daehyeon Ko <4ncienth@gmail.com> Thanks, Daehyeon