From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3F3EBC61DC2 for ; Wed, 26 Aug 2026 09:10:48 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 34D246B0096; Wed, 26 Aug 2026 05:10:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2FE7A6B0098; Wed, 26 Aug 2026 05:10:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1EE436B009B; Wed, 26 Aug 2026 05:10:47 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id ED5DF6B0096 for ; Wed, 26 Aug 2026 05:10:46 -0400 (EDT) Received: from smtpin29.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 7B2911202EE for ; Wed, 26 Aug 2026 09:10:46 +0000 (UTC) X-FDA: 85142850492.29.67DEDD3 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf27.hostedemail.com (Postfix) with ESMTP id 9BADE4000A for ; Wed, 26 Aug 2026 09:10:44 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=S9xyIhYe; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787735444; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=j3Se6vqnwz9wr7Aaoob8u5/g7nY4GxqOyEJVx124RT0=; b=fVAxzhWtEJbxYlVDW6DnnCAVfGBvSlVQ77Kfbk6suLDu+Mv/pnNPplKIFos8dr0aki+xbk rEVe5YLQCbIanG0I6/MQDpilNfC2uWc3hB7+drJJ5tJHBopyNbMGgULWFwzsTO5Blor8tx E0l2LduRA3O3PROU432CwUGo8PNlfkk= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787735444; b=TfZe315vpu3Ja12uqN45DiNuAP6OpSvLHN5dqhMa3XQSrPqcDaYYWNhk1IhnEtN7asFmxK Q8f3+NcT7uNkCLOQIF3/xmTNMdQ03XPIT977IjFjc5eFwsqJBaZiDxQ1878csuNtPARVMl mE7rh5Sg+jW8ULHwgqUVtUl+DfoDJ/8= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=S9xyIhYe; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id B87674092B; Wed, 26 Aug 2026 09:10:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 17AA61F000E9; Wed, 26 Aug 2026 09:10:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787735443; bh=j3Se6vqnwz9wr7Aaoob8u5/g7nY4GxqOyEJVx124RT0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=S9xyIhYe4imNUTEKw6+1shliq7P+QfPGrpzYLo8R2UykC5vV7VVD9WqqJGSdNoDZO m9ODscYqd1hFS5y/w4ef246uekUGi0pR4CBlKTPv64G9R91E0BZr2IVOEUoVJfbKG8 Tm/p/430vyQyn0ZgEeAFiNwaADtzO/JG0D38mXmxU60PLSgCcbcsKh9xk/TATdeFez f6MbiGPTwQhxrJaPQy5JViTs7WIFyfbaqjBcj2XwVSqj7ZT7spEGkHOqGWBfXwk6i3 qC4LWSz6xVmCH8vkhx4iKFbotldMVfe7B806ZQPcno5nCieHUp92Z/mDdSBO3+VES1 2LkR9BmZaGhcg== Message-ID: Date: Wed, 26 Aug 2026 11:10:37 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/3] mm: khugepaged: fix swap entry value to folio_pfn() To: "Lorenzo Stoakes (ARM)" Cc: Vernon Yang , akpm@linux-foundation.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, zokeefe@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, Vernon Yang References: <20260824092935.73892-1-vernon2gm@gmail.com> <20260824092935.73892-2-vernon2gm@gmail.com> <6a9c2369-5589-4f2a-bcfe-c6e3b46a1ccd@gmail.com> <42695df0-3962-4126-9afb-9a1905d096a0@kernel.org> <49aa013f-f613-42be-bc58-35956ef189de@kernel.org> 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: 7bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 9BADE4000A X-Stat-Signature: nzh3xi7x9tx3u867ib53qn6jh3pwnhua X-HE-Tag: 1787735444-820579 X-HE-Meta: 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 brePmNFF TKW0+ZGxdg2ug1Mcd3hKxTD6cvKpIbNQZTWC51F/7/CXHbBsfnB9ifUEiF0kGxt82BFbW9slgmKtdm9LPVWXwmlwFA2vxYT/2iPswMyntMsvPu4eucYMKxwrVuWbWtMX9Cy8beLEquzIvFNV87+asalDxQtlaMFjuqOzIVuwtoGk5YNrKX5IdR1/2BB+TevB4PLpT1aCicNpHh4mhdFjrfslb0rWzqoD/94+1uqMGLT274lrEi3HSt3DK97jVbm/Tv/wjYdQ5PUnu7taVduDmOhmDc22FZzyJkLK2eV2f9PCxvCq9rCRBLkhkXQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/26/26 10:35, Lorenzo Stoakes (ARM) wrote: > On Wed, Aug 26, 2026 at 10:24:56AM +0200, David Hildenbrand (Arm) wrote: >> On 8/26/26 10:16, David Hildenbrand (Arm) wrote: >>> >>> Excuse me, what? Are you now just making up arguments? >> To clarify, we have various users of "xxx_pfn" in the tree and I fail to see how >> "this is a problematic pfn" -> "problematic_pfn" is odd and why >> "pfn_problematic" would be any clearer. >> >> I do agree with the "problematic" aspect. "failed" might indeed be nicer. > > Right yeah. Mostly the push back is on the word being a bit confusing. Fair > enough on the pfn thing, failed_pfn is actually the nicest name suggested so far > :) > > I still think: > > if (result == SCAN_SUCCEED) { > ... > trace_mm_khugepaged_scan_file(mm, -1, file, present, swap, result); > } else { > trace_mm_khugepaged_scan_file(mm, failed_pfn, file, present, > swap, result); > } > > Is a little neater as then it's only on the failure path that we trace the > failed pfn, and otherwise we explicitly -1. > > But it's not exactly a show stopper this :) > > Very rough edit of your patch - if you're happy then let's go with this, if not > then edit it + post so Vernon has a clear direction. I'm not feeling super > strongly on this so don't want to block anything: > > ----8<---- > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 75639298efc27..371ee0b16d10c 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2683,6 +2683,7 @@ static enum scan_result collapse_scan_file(struct > mm_struct *mm, > int present, swap; > int node = NUMA_NO_NODE; > enum scan_result result = SCAN_SUCCEED; > + unsigned long failed_pfn = -1; > > present = 0; > swap = 0; > @@ -2714,6 +2715,7 @@ static enum scan_result collapse_scan_file(struct > mm_struct *mm, > } > > if (is_pmd_order(folio_order(folio))) { > + failed_pfn = folio_pfn(folio); > result = SCAN_PTE_MAPPED_HUGEPAGE; > /* > * PMD-sized THP implies that we can only try > @@ -2725,6 +2727,7 @@ static enum scan_result collapse_scan_file(struct > mm_struct *mm, > > node = folio_nid(folio); > if (collapse_scan_abort(node, cc)) { > + failed_pfn = folio_pfn(folio); > result = SCAN_SCAN_ABORT; > folio_put(folio); > break; > @@ -2732,12 +2735,14 @@ static enum scan_result collapse_scan_file(struct > mm_struct *mm, > cc->node_load[node]++; > > if (!folio_test_lru(folio)) { > + failed_pfn = folio_pfn(folio); > result = SCAN_PAGE_LRU; > folio_put(folio); > break; > } > > if (folio_expected_ref_count(folio) + 1 != folio_ref_count(folio)) { > + failed_pfn = folio_pfn(folio); > result = SCAN_PAGE_COUNT; > folio_put(folio); > break; > @@ -2773,7 +2778,7 @@ static enum scan_result collapse_scan_file(struct > mm_struct *mm, > } > - } > - trace_mm_khugepaged_scan_file(mm, folio, file, present, swap, result); > + trace_mm_khugepaged_scan_file(mm, -1, file, present, swap, > + SCAN_SUCCEED); > + } else { > + trace_mm_khugepaged_scan_file(mm, failed_pfn, file, present, > + swap, result); > + } > + > return result; > } That looks good to me, thanks. My memory is bad this week, so I have to ask with the fear of having asked before: is tracing the PFN of any value? What can someone tracing this on userspace reasonably do with the PFN? Inspect kpageflags? I'd assume someone actually doing that is quite ... rare. -- Cheers, David