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b=giD39Nh8WLWpBEfojs5C/SZCwFUs6PAMJqvIYhgfX7PMOL/oLbA/NKNtF+1A2K6O5 zgRZViH6ye5VxOLTrMhI3+PaS8zZTrDVENTGLgmaFtVs4YjZXI4C9oWbolXgtCZZqW Kway5HHWhsVZCGXLhF1QeSkKdrfJaoZVnzC6S9mMGc+8sL1/9nn4jwPciqRflu6krw HJoNWlZoAxM3HZ9yhzL6C85eVDsc8LKL7RIKGWpq5hY40VlyQSqiLuNG/7gBPFq8NL WJcgXwMmwZoeCzqYX8vDwfFPU14jL5pIHlQq6vDxo4yC8jmw4HSolH0EX8B2vun5nq GFLTEW8qPOzsw== From: SJ Park To: Miguel Ojeda Cc: SJ Park , gregkh@linuxfoundation.org, 4ncienth@gmail.com, akpm@linux-foundation.org, azpijr@gmail.com, corbet@lwn.net, david@kernel.org, jannh@google.com, liam@infradead.org, ljs@kernel.org, mhocko@suse.com, patches@lists.linux.dev, pfalcato@suse.de, rdunlap@infradead.org, rppt@kernel.org, sashal@kernel.org, shakeel.butt@linux.dev, stable@vger.kernel.org, surenb@google.com, vbabka@kernel.org, linux-mm@kvack.org, Dave Hansen Subject: Re: [PATCH 7.3 463/507] mm/vma: avoid spurious write locks when mm->mm_lock_seq overflows Date: Fri, 13 Nov 2026 19:19:42 -0800 Message-ID: <20261114031943.192867-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261114003912.82206-1-ojeda@kernel.org> References: X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Stat-Signature: totrdbc4u38mwgx6b37k5asi1o5sfwas X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: F25DFA0003 X-Rspam-User: X-HE-Tag: 1794626391-66437 X-HE-Meta: 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 Bq7TFNVn wYWwb279FgTp4ArXFuWy82mgTB/iwWiNUdx9MUvaVnHDBIgjqKObEVYVbT210rIizlfoilOfSH6oJXJKHqAEi/unJTzKQ73awzhZnYHCnCTm87ZG/WSK94OPTTmfExO0H8KyrpYYCFv8DAWK121YzKNSO49mbyqk2ZO0ZuHKjJmJ/JkR1qvKHTQ1ZwpvCXX9I80EDwCjJ6CowkF8Um8ukdwF+ODDJS2qAbKA4dtxvLwmaO4x/mZVSdfLJzG+Y/VuksHeqk9t2Tf+4JyPydqwbEyeZzcYPladcXhXWrx+OwTtTfxxoNB6RUCLYEGX9kuZnoLv2CLDjMyK84u2TYAg2XQEx3Q== 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 On Sat, 14 Nov 2026 01:39:12 +0100 Miguel Ojeda wrote: > On Fri, 13 Nov 2026 10:52:47 -0500 Greg Kroah-Hartman wrote: > > > > @@ -589,6 +593,16 @@ static inline void vma_end_write_all(struct mm_struct *mm) > > { > > mmap_assert_write_locked(mm); > > mm_lock_seqcount_end(mm); > > + > > + /* > > + * VMA seqcounts are not updated on unlock, so once the mm seqcount has > > + * wrapped, any VMA still carrying a sequence number from before the > > + * wrap would satisfy __is_vma_write_locked() when that number comes > > + * round again, and readers would not be excluded. Reset every VMA's > > + * seqcount so that no stale value survives the wrap. > > + */ > > + if (unlikely(!mm->mm_lock_seq.sequence)) > > + __mm_reset_vma_seqcounts(mm); > > } > > In a UM ~defconfig build with LLVM: > > In file included from arch/um/kernel/asm-offsets.c:8: > In file included from ./include/linux/audit.h:13: > In file included from ./include/linux/ptrace.h:10: > In file included from ./include/linux/pid_namespace.h:7: > In file included from ./include/linux/mm.h:18: > ./include/linux/mmap_lock.h:604:20: error: no member named 'mm_lock_seq' in 'struct mm_struct' > 604 | if (unlikely(!mm->mm_lock_seq.sequence)) > | ~~ ^ > ./include/linux/compiler.h:77:42: note: expanded from macro 'unlikely' > 77 | # define unlikely(x) __builtin_expect(!!(x), 0) > | > > That exists only under `CONFIG_PER_VMA_LOCK` (commit 47e725702b0b ("mm: > make per-VMA locks available universally") from Dave's series was not > backported). I found same thing while running kunit. I also confirmed both applying commit 47e725702b0b from Dave and reverting this patch fix the problem on my setup. Thanks, SJ [...]