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Mon, 26 Jan 2026 13:42:00 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 8lTDLShvd2nIZAAAD6G6ig (envelope-from ); Mon, 26 Jan 2026 13:42:00 +0000 Message-ID: <6c4162c5-1703-45db-b9ca-96ecd8ce551f@suse.cz> Date: Mon, 26 Jan 2026 14:42:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 09/10] mm/vma: update vma_assert_locked() to use lockdep Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: David Hildenbrand , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shakeel Butt , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt References: <538762f079cc4fa76ff8bf30a8a9525a09961451.1769198904.git.lorenzo.stoakes@oracle.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <538762f079cc4fa76ff8bf30a8a9525a09961451.1769198904.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: w4fdpfgscwdkchwb5u757zoabjcwqm5c X-Rspamd-Queue-Id: 9A8C7C0002 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1769434922-539066 X-HE-Meta: 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 CxL3Ak4g CylQm0wBog29wL3VdbdGCkHsgwd+PEVaiG9Cvp4W63OHMDkDQii3rLcJu5OCPwefg8wy5za5vQZ9UQI69g1egyHv+e8tpk0V1bD45BT1z7pexg0z4HJpQ8mWenMl/w9C/CUBBHrNbFRHQJZJUS4Jw8hhwn8PQga3daKqeExlExiS4RowkaAoo48odepetnz5yMO5SXA77niWPW7EZ99yLVTycYUl/asYUhTfIRWZ0urb97wqa5cXSX15XYxFRIUOrvEx0uWmJrgHyqeTbAlutnU4ijLZRy1HNQvEefnf33jmswA7L8vDlGkUb2P6JEh1XpKMpCneZGJYCDOhYcdsymeFZpglydvZ0r8rclWdKrEjc7Dx1COkHKKv7n+6MAU6+v5622/leHix8SLyN+iTSOIa3Pp5S9kzYTRMAIYSJF1sAY+F0AV1yWLC6famK8v7JXrPOhtqedBMQeWk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1/23/26 21:12, Lorenzo Stoakes wrote: > We can use lockdep to avoid unnecessary work here, otherwise update the > code to logically evaluate all pertinent cases and share code with > vma_assert_write_locked(). > > Make it clear here that we treat the VMA being detached at this point as a > bug, this was only implicit before. > > Reviewed-by: Suren Baghdasaryan > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Nit: > --- > include/linux/mmap_lock.h | 41 +++++++++++++++++++++++++++++++++++++-- > 1 file changed, 39 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h > index 23bde4bd5a85..4a0aafc66c5d 100644 > --- a/include/linux/mmap_lock.h > +++ b/include/linux/mmap_lock.h > @@ -322,19 +322,56 @@ int vma_start_write_killable(struct vm_area_struct *vma) > return __vma_start_write(vma, __vma_raw_mm_seqnum(vma), TASK_KILLABLE); > } > > +/** > + * vma_assert_write_locked() - assert that @vma holds a VMA write lock. > + * @vma: The VMA to assert. > + */ > static inline void vma_assert_write_locked(struct vm_area_struct *vma) > { > VM_WARN_ON_ONCE_VMA(!__is_vma_write_locked(vma), vma); > } > > +/** > + * vma_assert_locked() - assert that @vma holds either a VMA read or a VMA write > + * lock and is not detached. > + * @vma: The VMA to assert. > + */ > static inline void vma_assert_locked(struct vm_area_struct *vma) > { > + unsigned int refcnt; > + > + /* > + * If read-locked or currently excluding readers, then the VMA is > + * locked. > + */ > +#ifdef CONFIG_LOCKDEP > + if (lock_is_held(&vma->vmlock_dep_map)) > + return; Wouldn't this work a tiny bit better? if (!lock_is_held(&vma->vmlock_dep_map)) vma_assert_write_locked(vma); return; > +#endif > + > /* > * See the comment describing the vm_area_struct->vm_refcnt field for > * details of possible refcnt values. > */ > - VM_WARN_ON_ONCE_VMA(refcount_read(&vma->vm_refcnt) <= 1 && > - !__is_vma_write_locked(vma), vma); > + refcnt = refcount_read(&vma->vm_refcnt); > + > + /* > + * In this case we're either read-locked, write-locked with temporary > + * readers, or in the midst of excluding readers, all of which means > + * we're locked. > + */ > + if (refcnt > 1) > + return; > + > + /* It is a bug for the VMA to be detached here. */ > + VM_WARN_ON_ONCE_VMA(!refcnt, vma); > + > + /* > + * OK, the VMA has a reference count of 1 which means it is either > + * unlocked and attached or write-locked, so assert that it is > + * write-locked. > + */ > + vma_assert_write_locked(vma); > } > > static inline bool vma_is_attached(struct vm_area_struct *vma)