From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7DA0F4AD7E0; Fri, 11 Sep 2026 17:52:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789149169; cv=none; b=V/F29lZRyB36GfcQF1lxA+x8wWnvwdHkZGKVS+Ev3w+PYgQCMRBKcVYkUN+wWijexRVQ2DQ9y16MfPOZWNT9hc9jUBKQaxTTwoWhM84ya8JdcARmbNn7D82Ix3BmLJcwWNElq9osyDwRaU6UsNqxp5/pc2eqtWWtGFAwEqBLJWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789149169; c=relaxed/simple; bh=0zc27GoCKWrFtSsA2UdRwu5+iVQ7K9sCnP+jlIM2HqQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OuaLKIPfe2dlQEiWI77LSmrKvmjhzWqSlD/x1+nJde8m2JtLQ+KYzD9hhviZyfOgD+WJ/+cIHzR4Q/pkh67T+IaRCR/hXToDlUV0SstHMUfmjPZR9GCEHrDuO61sowwikzzD+O7LR9YFccUXd21bO76LvtZ7ahH0e93VMvYCdCw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iOz351Q/; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iOz351Q/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96D4F1F000FF; Fri, 11 Sep 2026 17:52:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789149166; bh=iVpZfsXMVEGiEUfVriw9pLF8pscFPyVWyCdcfJ25DGc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=iOz351Q/hnr3UJVmku9z13YS0k8WM/um8sWugkCDEQ3q8R8SlKuwrn1Y9lnc1yzMe 4FriItsqCkS5TYFvlF64mmdFpYcVXCQjR9wpBEZe7Kf2QhLpFWQynplSJmn3agr/fx PXiAeZgHdkJ/fmy8vLoM69lSaQXBV+UnzEcxamARhjEObcJrBsx2TkXcX62YwzMjxL SwrGn7bW/qrJphLTeoAyqj9cFf6u636d3MhMHvM0MKKVPNKSGUWOgaQ5yPdx+ib9Ej b6JAzN+cbNoOlbrLwew+3sDhnK/dI5sD2FRfSKXwg93F5F4n9x3RWHQtfDdv0dmPDQ O/NBvf81QRXzw== Message-ID: Date: Fri, 11 Sep 2026 19:52:38 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/7] proc/task_mmu: clarify shmem mapping walk conditions in smap_gather_stats() To: Suren Baghdasaryan , "Lorenzo Stoakes (ARM)" Cc: akpm@linux-foundation.org, liam@infradead.org, vbabka@kernel.org, willy@infradead.org, jannh@google.com, paulmck@kernel.org, pfalcato@suse.de, xueyuan.chen21@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20260910234737.1340642-1-surenb@google.com> <20260910234737.1340642-4-surenb@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 9/11/26 19:39, Suren Baghdasaryan wrote: > On Fri, Sep 11, 2026 at 10:10 AM Lorenzo Stoakes (ARM) wrote: >> >> On Fri, Sep 11, 2026 at 04:58:40PM +0000, Suren Baghdasaryan wrote: >>> >>> Well, the "other" Lorenzo does not agree with you and suggested this >>> approach in [1]. Specifically, see the comment: >>> ``` >>> I also don't love that 0 is taken to be 'start from vma->vm_start' and I >>> also don't love that the code in smap_gather_stats() actually special cases >>> this... >> >> I'm not sure what part of this is disagreement? >> >> It's saying passing 0 is a hack, which is one that is still in place and which >> this patch makes worse, because instead of explicitly calling out the invalid >> value, you're treating it as if it were valid. >> >>> >>> How about passing last_vma_end and making smap_gather_stats() more sane? In >>> the other invocation of smap_gather_stats() we could pass vma->vm_start >>> here. >> >> Yup, well me of 3 months ago should have suggested what I suggested re: wrapper >> (I think you cut that suggestion out of my reply). >> >>> ``` >>> >>> [1] https://lore.kernel.org/all/aifO_rCurVhFRTcl@lucifer/ >> >>> >>> >>> See [1]. This is exactly how you wrote it at the end of that reply. >> >> Assuming you passed vma->vm_start, not 0? Passing 0 makes it really strange. > > Ah! Now I see the problem you are pointing out. Ok, in v2 [2] this was > done correctly and that's the way you want it! > Okay, I agree this split was incorrect. I think I'll move is_partial > conversion completely into the next patch and this one will only > update the comment and use vma_is_cow_mapping() instead of open-coding > it. Ah, that makes sense, I missed that as I was mostly focusing on the cow stuff only. -- Cheers, David