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Mon, 26 Jan 2026 10:12:36 +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 OuaeOhQ+d2lXCgAAD6G6ig (envelope-from ); Mon, 26 Jan 2026 10:12:36 +0000 Message-ID: Date: Mon, 26 Jan 2026 11:12:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 03/10] mm/vma: rename is_vma_write_only(), separate out shared refcount put 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: <32053580bff460eb1092ef780b526cefeb748bad.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: <32053580bff460eb1092ef780b526cefeb748bad.1769198904.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 4w739nx169c8anmq9wwfoocb8uof1g6e X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 71CBF40002 X-HE-Tag: 1769422359-686128 X-HE-Meta: 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 Gp4pESiO q37KydqHzm36mZQYA11sLLDfSFX8mtXYdWf4LmtS2Z4gxEz7bV9MPNh5eRMDKbVbALrljEwdWckjXcwmVeSpbC1XlykNahhTbEh3N8uQMLpUNdjDCayuu9MotLYv7CqPARCPGCC0iWXaDqRO8eKtYgC4/XmWiyBcMd/8tm8bziL5nYqnDHMKsWDf6+nZibM0iblSslAPDAOMLdIA7YfxUF7g2imOEEfnlE1ASD7Gz4q8AbX8u+BsKUkosd5RVPeXF53aI0rqWPsbisFx1dfKswqtJchHVY3arAl9Sd4iJWF1MQwCtImqN+KNTFwLkZHXOoOc5ztyPMbaz/aC6A1mEdvLNyC6eUSakfWvm47TgMJMWrCB4DZ2kCgETmjPNOSQOdAd09FJ0F09RO7M+TYbuc1dzakqDsuaHODbdrKLfOWwxHDc= 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: > The is_vma_writer_only() function is misnamed - this isn't determining if > there is only a write lock, as it checks for the presence of the > VM_REFCNT_EXCLUDE_READERS_FLAG. > > Really, it is checking to see whether readers are excluded, with a > possibility of a false positive in the case of a detachment (there we > expect the vma->vm_refcnt to eventually be set to > VM_REFCNT_EXCLUDE_READERS_FLAG, whereas for an attached VMA we expect it to > eventually be set to VM_REFCNT_EXCLUDE_READERS_FLAG + 1). > > Rename the function accordingly. > > Relatedly, we use a __refcount_dec_and_test() primitive directly in > vma_refcount_put(), using the old value to determine what the reference > count ought to be after the operation is complete (ignoring racing > reference count adjustments). > > Wrap this into a __vma_refcount_put_return() function, which we can then > utilise in vma_mark_detached() and thus keep the refcount primitive usage > abstracted. > > This function, as the name implies, returns the value after the reference > count has been updated. > > This reduces duplication in the two invocations of this function. > > Also adjust comments, removing duplicative comments covered elsewhere and > adding more to aid understanding. > > No functional change intended. > > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka