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Wed, 28 Jan 2026 13:01:42 +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 OhtXKbYIemmgJwAAD6G6ig (envelope-from ); Wed, 28 Jan 2026 13:01:42 +0000 Message-ID: Date: Wed, 28 Jan 2026 14:01:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 08/10] mm/vma: improve and document __is_vma_write_locked() Content-Language: en-US To: Lorenzo Stoakes , Suren Baghdasaryan Cc: Andrew Morton , David Hildenbrand , "Liam R . Howlett" , Mike Rapoport , 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: <47eafa10-6d13-4324-830a-2e7cf4e67f2b@suse.cz> <6444753e-1df7-4732-912a-0ea441f76cb1@lucifer.local> <425e3040-0522-4af1-a7b9-c9ad04e017e8@lucifer.local> 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: <425e3040-0522-4af1-a7b9-c9ad04e017e8@lucifer.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: 01AA920012 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: hom8p844hu14sfa61pmeic7guy1npqq8 X-HE-Tag: 1769605305-151037 X-HE-Meta: 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 gKWh4GOn +3nfTli1HLD59WxWwYvDxxW9O4MLUbdEwQOdPq7r375eVNsk= 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 1/28/26 12:51, Lorenzo Stoakes wrote: >> >> > >> > Thanks! >> > >> > > >> > > Few nits: >> > > >> > > > --- >> > > > include/linux/mmap_lock.h | 44 ++++++++++++++++++++++----------------- >> > > > 1 file changed, 25 insertions(+), 19 deletions(-) >> > > > >> > > > diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h >> > > > index 678f90080fa6..23bde4bd5a85 100644 >> > > > --- a/include/linux/mmap_lock.h >> > > > +++ b/include/linux/mmap_lock.h >> > > > @@ -258,17 +258,30 @@ static inline void vma_end_read(struct vm_area_struct *vma) >> > > > vma_refcount_put(vma); >> > > > } >> > > > >> > > > -/* WARNING! Can only be used if mmap_lock is expected to be write-locked */ >> > > > -static inline bool __is_vma_write_locked(struct vm_area_struct *vma, unsigned int *mm_lock_seq) >> > > > +static inline unsigned int __vma_raw_mm_seqnum(struct vm_area_struct *vma) >> >> This function returns the mm->mm_lock_seq.sequence attribute of mm, so >> no real commection to VMA. IMO it's better to rename it into >> __raw_mm_lock_seqnum(const struct mm_struct *mm) and have the callers >> pass vma->vm_mm. > > Sorry missed these comments. > > We are only ever referencing in terms of VMA's, so I think it makes sense still > to pass a VMA ptr, even if it just references vma->vm_mm. FWIW I agree. > I think the name of the function also makes things pretty clear, given it's > called essentially 'VMA['s] raw mm seqnum'. > >> >> > > > { >> > > > + const struct mm_struct *mm = vma->vm_mm; >> > > > + >> > > > + /* We must hold an exclusive write lock for this access to be valid. */ >> > > > mmap_assert_write_locked(vma->vm_mm); >> >> If for some reason you need to keep this function VMA-centric, then in >> the above line please s/vma->vm_mm/mm > > Ah yeah, maybe if there's a respin? As kinda trivial thing, if that makes sense > to you! > > Cheers, Lorenzo