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Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , David Hildenbrand , Xu Xin , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Stefan Roesch Subject: Re: [PATCH v3 3/4] mm: prevent KSM from breaking VMA merging for new VMAs Message-Id: <20250622123931.30b1739642be8ec1e9ca04e2@linux-foundation.org> In-Reply-To: <5861f8f6-cf5a-4d82-a062-139fb3f9cddb@lucifer.local> References: <3ba660af716d87a18ca5b4e635f2101edeb56340.1748537921.git.lorenzo.stoakes@oracle.com> <5861f8f6-cf5a-4d82-a062-139fb3f9cddb@lucifer.local> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6438A1A0006 X-Stat-Signature: aykrs99r78dppx37s5uatxedxss7xexp X-Rspam-User: X-HE-Tag: 1750621173-172581 X-HE-Meta: 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 8qGcij0U J80z+2swEZGcA22aIHYJwumDXbx25fYi/4r6+CtkwcdZjmf7qhQQ5DACMX7k+2dGCDRz+2oPw5MzMiJvxPNIuGZ2ByZclaXamoGu+OhI4Gv0joXvqmakZq2YZRFjHWPkJz6cq09zUWWQ1mINz4vIFZl+Axwx53Kt8iiqCmQUMtkiUbY6t/lq+DK0Ok06dZTPG1FAk9wm34esKMw6p4ellC9fSchCwmoaBwiKahtzdJD2uZ9gZnkhgVav3Mqdkozyi1ttWgYIkeaPZyfzaGl7t8gJj4whW2pbCCLDNXrdYQ9I4xss= 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 Fri, 20 Jun 2025 13:48:09 +0100 Lorenzo Stoakes wrote: > Hi Andrew, > > Sending a fix-patch for this commit due to a reported syzbot issue which > highlighted a bug in the implementation. > > I discuss the syzbot report at [0]. > > [0]: https://lore.kernel.org/all/a55beb72-4288-4356-9642-76ab35a2a07c@lucifer.local/ > > There's a very minor conflict around the map->vm_flags vs. map->flags change, > easily resolvable, but if you need a respin let me know. I actually saw 4 conflicts, fixed various things up and... > @@ -2487,6 +2496,11 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap) > if (error) > goto free_iter_vma; > > + if (!map->check_ksm_early) { > + update_ksm_flags(map); > + vm_flags_init(vma, map->vm_flags); > + } > + Guessing map->flags was intended here, I made that change then unmade it in the later mm-update-core-kernel-code-to-use-vm_flags_t-consistently.patch. I'll do a full rebuild at a couple of bisection points, please check that all landed OK.