From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1C209396B91; Mon, 9 Mar 2026 11:50:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773057049; cv=none; b=NteKaSaA2wS2XIsOJPjs1bjYifrQ9U+xpYa5nedtH9hz04zLIHDqeiRC6gWEo7YcWpFfQsmK/mZXR/PhlsbmOMTj/a0+uFmGsjM0MfFtbCE2roHE6ePie62YqyIkcLYZF8xjIf5HWktKd4sYHmwVepBxlzhymXmk05pt2o96qPw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773057049; c=relaxed/simple; bh=MKDoMhatF/8bmNy6+4wMS5v8ebUxjWldeMUyNsD//UI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NdtbEumfnRERw/103lpxuhDIIAPn8CduGyB7l6pBgwRKgZ4NzX3Cf6XJiHZ3rreNTJz0ExkE/NdlLbM9pSUSjmaUryH9UjpFeR46OmO0D/Q4WPYErIQFVUGYE3Nf0nu7t9gdBIpRNUq0TcpAvsHRqVOTAYpXBDQMzQY6LmfDabc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=doD57pDQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="doD57pDQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B42C9C4CEF7; Mon, 9 Mar 2026 11:50:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773057048; bh=MKDoMhatF/8bmNy6+4wMS5v8ebUxjWldeMUyNsD//UI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=doD57pDQPBLH+3BvqxHLNZmaR1BBbeo4If0RPfIqWfW5Z9lEi02liWOf9Tv5JUrie ufUKiMb9aOonEeLiXnITDfuCrjFo2knisrJoDRPa2HHhr6g8Q34rbFcr5+o53EhB8M 16h/9igRBjHnzQ2hS7sn2zNZnATj63YIOQZ9kLADwIU6Gp/u4v3jiTIak7wA7mfvvN H7N6uwroorzCmuYVAqpQkgzQ1JId2xSIUTWrqXr+DUUMeugtAo2SA2Td2567bFhNnl 1sq4SYFMELF9394s1kh9A7kMe7MT5K7PVP5Tgmp8NnZFRSLsW3fP9GfdtSjasR6HXT Cf1PYT7f1gP3A== Message-ID: <577c4725-7eda-4693-a55a-413572541161@kernel.org> Date: Mon, 9 Mar 2026 12:50:36 +0100 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v3 1/4] KVM: guest_memfd: Track amount of memory allocated on inode To: Ackerley Tng , Paolo Bonzini , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Shuah Khan , Jonathan Corbet , Alexander Viro , Christian Brauner , Jan Kara , seanjc@google.com, rientjes@google.com, rick.p.edgecombe@intel.com, yan.y.zhao@intel.com, fvdl@google.com, jthoughton@google.com, vannapurve@google.com, shivankg@amd.com, michael.roth@amd.com, pratyush@kernel.org, pasha.tatashin@soleen.com, kalyazin@amazon.com, tabba@google.com, Vlastimil Babka Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org References: <20260309-gmem-st-blocks-v3-0-815f03d9653e@google.com> <20260309-gmem-st-blocks-v3-1-815f03d9653e@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: <20260309-gmem-st-blocks-v3-1-815f03d9653e@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/9/26 10:53, Ackerley Tng wrote: > The guest memfd currently does not update the inode's i_blocks and i_bytes > count when memory is allocated or freed. Hence, st_blocks returned from > fstat() is always 0. > > Introduce byte accounting for guest memfd inodes. When a new folio is > added to the filemap, add the folio's size. Use the .invalidate_folio() > callback to subtract the folio's size from inode fields when folios are > truncated and removed from the filemap. > > Signed-off-by: Ackerley Tng > --- > virt/kvm/guest_memfd.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 462c5c5cb602a..77219551056a7 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -136,6 +136,9 @@ static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index) > mapping_gfp_mask(inode->i_mapping), policy); > mpol_cond_put(policy); > > + if (!IS_ERR(folio)) > + inode_add_bytes(inode, folio_size(folio)); > + Can't we have two concurrent calls to __filemap_get_folio_mpol(), and we don't really know whether our call allocated the folio or simply found one (the other caller allocated) in the pagecache? -- Cheers, David