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 B7BD9C61DBD for ; Wed, 26 Aug 2026 08:35:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AB23A6B008C; Wed, 26 Aug 2026 04:35:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A62B06B0092; Wed, 26 Aug 2026 04:35:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 978386B0096; Wed, 26 Aug 2026 04:35:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 6BCF56B008C for ; Wed, 26 Aug 2026 04:35:48 -0400 (EDT) Received: from smtpin06.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id E0EBF1402D5 for ; Wed, 26 Aug 2026 08:35:47 +0000 (UTC) X-FDA: 85142762334.06.5933D2F Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf18.hostedemail.com (Postfix) with ESMTP id 508BC1C0006 for ; Wed, 26 Aug 2026 08:35:46 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=UIMIbuVi; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf18.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787733346; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=77HcB1kud9ZQLGTOBXm8D/IPatt20bqt7WcnuYLsxnw=; b=o0Dh/X1E3jeFvCdax6P/IiWwVDQc7eNFQavAhgJckPUMi/NrHXouSN7yLGWuQqk5uAmYQj iSJTkv3IrG1g95MgLdIM0W7Okm5UGOjODQ5zzuMK4QYATnVl5FbSy2ssFaWg1vsWg3qovq V5VXW86i5KyVVxmVtYAsNd5Jna/9rKA= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=UIMIbuVi; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf18.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787733346; b=6vpUj8ccvGme6KReMmdbDAIcO/rQhVMQau/IFkZMSzD0wSJfzALNlw3W7MkBRw3V6WuDZk Y7O1tSkhT/kSVCedVjkaLlk0WixOurkHYJZTPZKVsLKwjSKc1y5sx69fB/IvEX/Wz3K5mr qnDoYZKJRH38eh+dSluMNXzd6uNwtiA= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 5761760A5C; Wed, 26 Aug 2026 08:35:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9274F1F000E9; Wed, 26 Aug 2026 08:35:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787733345; bh=77HcB1kud9ZQLGTOBXm8D/IPatt20bqt7WcnuYLsxnw=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=UIMIbuVicIoSiAAGWpoipJ+A4fWtYWgCwo1Ax/57fBrKhMb/kTfwyKH/nvzE+dDm5 22svvHl7hnd7BnokCEJrA4QsJjQ1TfoN9LY/lTmC07NROJeFbQelbqXkmjJIDLb/fK YB6hcym6o463vUIu2Dbri4qeJ6KVfRlrIhbpfGcZ6hcJa1CkNKPBJD4OCmzvWMWVtv my1sGLHZNNK2a6shTrF3tQG4FL1vqOQ89D4WgyOMxXrjYJnSD/xEf00C2VLLIhqVGX CUS0xhzW6shZ1SWWyGjz2TjtSLChnhTAOhwu5NuYXMJxTdOzpM5cMVlS5f5WDwyvdD oL0YKWmxACJ3w== Date: Wed, 26 Aug 2026 09:35:38 +0100 From: "Lorenzo Stoakes (ARM)" To: "David Hildenbrand (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 Subject: Re: [PATCH v3 1/3] mm: khugepaged: fix swap entry value to folio_pfn() Message-ID: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49aa013f-f613-42be-bc58-35956ef189de@kernel.org> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 508BC1C0006 X-Stat-Signature: aas7tcgs3j7ptuau144ieikjqbbt7zgr X-Rspam-User: X-HE-Tag: 1787733346-336092 X-HE-Meta: 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 KQMNM1rR Zk5vNVZBbB2AwhIahVjD+OOEb13GMXfJRxehOJ4X0zy/YFHS7z5j7JRtqTLIdbT767GMUwLdnXUiCd44/DkdszeG5hSKNVBZICS2lVtqruCbij0l2BJXcihRDEbXS1RJJUrX/kSXTd3EoQlf1Nw6RgJ8yd9pAp+BVGvCLUYLVYS0G2LEXZyVkjjPxCJ6r0ToYK8rj1rKwL+WNT3r+tiHzwzZhLjrAlyncVsHGwEsRXob7CmjaWSEbwlGLfpRjLu6fCrDYP1XSOm+Xiw1mQFC0hRD5cQ65fI4+LqgUJCxC7o2AmeU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 26, 2026 at 10:24:56AM +0200, David Hildenbrand (Arm) wrote: > On 8/26/26 10:16, David Hildenbrand (Arm) wrote: > > On 8/26/26 10:11, Lorenzo Stoakes (ARM) wrote: > >> On Wed, Aug 26, 2026 at 10:08:58AM +0200, David Hildenbrand (Arm) wrote: > >>> > >>> Elaborate. > >> > >> It's overly long, I read it and am confused as to what is 'problematic' or not, > >> it reads weirdly in English and pfn_xxx is the usual convention for naming of > >> pfn's anyway. > > > > 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; } -- Cheers, Lorenzo