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Howlett" , Vlastimil Babka , Shakeel Butt , Jann Horn , Pedro Falcato , Lance Yang , "David Hildenbrand (Arm)" , "Kiryl Shutsemau (Meta)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Seunghyun An Subject: Re: [PATCH] mm/vma: predicate vma_assert_stabilised() on CONFIG_DEBUG_VM Message-ID: References: <20261110-vma-fixup-debug-asserts-v1-1-0b2e0680cd7e@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: C30D64000F X-Stat-Signature: 7br1ubw1q71r4yhqxxs8zbmtnhusef5g X-Rspam-User: X-Spam-Status: No, score=-10.8 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 autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794328796-931157 X-HE-Meta: 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 dFEDPip1 zbYuxY8j2IwXVhGRSL3yI0OVWP9jn1PWRMsstXS94HIn9eCs4lWQfx9MYLug3JHmmb3c9Pdq24byMGX2XSPoFo+PDoUEorIaDKEgBPmNguQYnm9Q+FD+NIHM7YT2wy6hgLvoDVL9ueawm+cZ4JV4n9ft9PtFrTuSJ1BjtYm5G3Pw3GHnCPcpPxHpTtOTghtyc3SBlCiFdE98xwL0gv15NLBuWzPCTx4QH2Nwo8U26zZ3eirfc+mqQXtgPc7X2rvjNW2l8E6g6MXzE6pOn/hfPdv4iUDskKc8Az3krQNGUo4BO7u8= 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 Tue, Nov 10, 2026 at 04:18:35PM +0000, Lorenzo Stoakes (ARM) wrote: > On Tue, Nov 10, 2026 at 04:07:48PM +0000, Lorenzo Stoakes (ARM) wrote: > > Andrew - could you update as below? > > > > Thanks! > > > > On Tue, Nov 10, 2026 at 03:10:40PM +0000, Lorenzo Stoakes (ARM) wrote: > > [ ... ] > > > diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h > > > index 9ccbbcbd7aca..9c3a9c6525c1 100644 > > > --- a/include/linux/mmap_lock.h > > > +++ b/include/linux/mmap_lock.h > > [ ... ] > > > /** > > > * vma_assert_stabilised() - assert that this VMA cannot be changed from > > > * underneath us either by having a VMA or mmap lock held. > > > @@ -418,9 +423,18 @@ static inline void vma_assert_locked(const struct vm_area_struct *vma) > > > * > > > * With lockdep disabled we may sometimes race with other threads acquiring the > > > * mmap read lock simultaneous with our VMA read lock. > > > + * > > > + * Assert only if CONFIG_DEBUG_VM is set. > > Also this should say: > > 'Assert only if CONFIG_DEBUG_VM or CONFIG_LOCKDEP is set.' > > > > */ > > > static inline void vma_assert_stabilised(const struct vm_area_struct *vma) > > > { > > > + if (!IS_ENABLED(CONFIG_DEBUG_VM)) > > > > Actually I think this should be: > > > > if (!IS_ENABLED(CONFIG_DEBUG_VM) || !IS_ENABLED(CONFIG_LOCKDEP)) > > Sorry this should be... > > if (!IS_ENABLED(CONFIG_DEBUG_VM) && !IS_ENABLED(CONFIG_LOCKDEP)) > > (I have a bit of a fever today, can you tell? :P) > > Thanks! OK OK actually. Sorry. The change isn't required, it's fine :P Please leave the patch as it is. If !CONFIG_DEBUG_VM but CONFIG_LOCKDEP we don't actually assert anything. Since this: if (IS_ENABLED(CONFIG_LOCKDEP)) { if (lockdep_is_held(&vma->vm_mm->mmap_lock)) return; } Is the only thing that would run in the functino and early-exit if the condition is hit. Then it defers to vma_assert_locked() which then reaches: if (IS_ENABLED(CONFIG_LOCKDEP)) { if (!lock_is_held(__vma_lockdep_map(vma))) vma_assert_write_locked(vma); return; } And vma_assert_write_locked() uses VM_WARN_ON_ONCE_VMA(). (flu vaccine on sunday, seems to have impacted my brain :P) -- Cheers, Lorenzo