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Thu, 19 Jun 2025 13:44:21 +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 ozIYIjUUVGgmFQAAD6G6ig (envelope-from ); Thu, 19 Jun 2025 13:44:21 +0000 Message-ID: <7a1d94ca-65a1-4b60-83a7-055c69d5c882@suse.cz> Date: Thu, 19 Jun 2025 15:44:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/vma: use vmg->target to specify target VMA for new VMA merge Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: "Liam R . Howlett" , Jann Horn , Pedro Falcato , Kees Cook , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250613184807.108089-1-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: <20250613184807.108089-1-lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam03 X-Stat-Signature: 6mjeaxe71a7oqsykaskma8ajycssu56m X-Rspam-User: X-Rspamd-Queue-Id: 44A6C20007 X-HE-Tag: 1750340663-867338 X-HE-Meta: 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 3vQeZLJW 06gCXSGFvABi7Bx4n5aRMo+MdTHDMl7a2by/Thn64MHAWBFkBaTwNa+YwTw40AyGnOtvmGBA4HLfHor8az6qeFk+WmNbgzJctteE7a6yvBi2Mdm4SW2X+e9bSXsS5plkIGmo8Jt15fLNbG3XJ7w9JVg7dckdXSBKBu+D3LIHeV2n85nmGw+Y7ErKbWmp6IRdzEwERm3n3GcdG9ZJrqCpSHB5TBcxJBJMwTtbPAois99EZClm0Eaj8pgD2my4Tg/lO7xFIxsWCLdAWzCJlIkvO6DYQk3x9Dnv/tcEHPret0ToTYyqdzJEg/Y1vMg== 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 6/13/25 20:48, Lorenzo Stoakes wrote: > In commit 3a75ccba047b ("mm: simplify vma merge structure and expand > comments") we introduced the vmg->target field to make the merging of > existing VMAs simpler - clarifying precisely which VMA would eventually > become the merged VMA once the merge operation was complete. > > New VMA merging did not get quite the same treatment, retaining the rather > confusing convention of storing the target VMA in vmg->middle. > > This patch corrects this state of affairs, utilising vmg->target for this > purpose for both vma_merge_new_range() and also for vma_expand(). > > We retain the WARN_ON for vmg->middle being specified in > vma_merge_new_range() as doing so would make no sense, but add an > additional debug assert for setting vmg->target. > > This patch additionally updates VMA userland testing to account for this > change. > > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Nit below: > @@ -1086,27 +1087,29 @@ struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg) > * @vmg: Describes a VMA expansion operation. > * > * Expand @vma to vmg->start and vmg->end. Can expand off the start and end. > - * Will expand over vmg->next if it's different from vmg->middle and vmg->end == > - * vmg->next->vm_end. Checking if the vmg->middle can expand and merge with > + * Will expand over vmg->next if it's different from vmg->target and vmg->end == > + * vmg->next->vm_end. Checking if the vmg->target can expand and merge with > * vmg->next needs to be handled by the caller. > * > * Returns: 0 on success. > * > * ASSUMPTIONS: > - * - The caller must hold a WRITE lock on vmg->middle->mm->mmap_lock. > - * - The caller must have set @vmg->middle and @vmg->next. > + * - The caller must hold a WRITE lock on vmg->target->mm->mmap_lock. The assert uses vmg->mm so maybe the comment should do the same? (IIRC mm was added only later to vmg?) > + * - The caller must have set @vmg->target and @vmg->next. > */ > int vma_expand(struct vma_merge_struct *vmg) > { > struct vm_area_struct *anon_dup = NULL; > bool remove_next = false; > - struct vm_area_struct *middle = vmg->middle; > + struct vm_area_struct *target = vmg->target; > struct vm_area_struct *next = vmg->next; > > + VM_WARN_ON_VMG(!target, vmg); > + > mmap_assert_write_locked(vmg->mm); > > - vma_start_write(middle); > - if (next && (middle != next) && (vmg->end == next->vm_end)) { > + vma_start_write(target); > + if (next && (target != next) && (vmg->end == next->vm_end)) { > int ret; > > remove_next = true;