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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0AF60C001B0 for ; Fri, 11 Aug 2023 03:09:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6B2F66B0074; Thu, 10 Aug 2023 23:09:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 663706B0078; Thu, 10 Aug 2023 23:09:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 52B986B007B; Thu, 10 Aug 2023 23:09:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 4438B6B0074 for ; Thu, 10 Aug 2023 23:09:03 -0400 (EDT) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id E9182120356 for ; Fri, 11 Aug 2023 03:09:02 +0000 (UTC) X-FDA: 81110342124.18.B8D0A89 Received: from mail-lj1-f176.google.com (mail-lj1-f176.google.com [209.85.208.176]) by imf13.hostedemail.com (Postfix) with ESMTP id 0AF1F2001F for ; Fri, 11 Aug 2023 03:08:59 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=yl5y7atS; spf=pass (imf13.hostedemail.com: domain of yosryahmed@google.com designates 209.85.208.176 as permitted sender) smtp.mailfrom=yosryahmed@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1691723340; 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=G8YBwS2ISUNabVdCBzJa481Mq/UZwGsjfMQseGixYF4=; b=o8ZxxPjU4PBC99lR1BRCBWGsl0PEVb72EXNXnbFEP+V1l/3BUsCLY/K9ZlyVoeX7za9cy7 Pj3cYn/galOX7Rj6etjo3HbFcUwBYTwaw99UL/EMoBeghoIb15jbduL78auz4K4Wz/VCPD 0DSK17BYuNzBaSX5mOekxhu1LFtCd1M= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1691723340; a=rsa-sha256; cv=none; b=qSrAyNAKPqygGJUx+ZtM7SG3UZ+/r1RaTkmm8uC0FPTcvPM9E+tDfgJR5794Lm9qTx2u1x zCnZwcr4sL9wq2m2i+knPYvnFa/VuKiDaCsWvDnWoCE6lHafLpztCtD4X/1+FTSJD6gq5q 6UKefr0rinv59NO7G9nzeyN8nm3ZyMs= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=yl5y7atS; spf=pass (imf13.hostedemail.com: domain of yosryahmed@google.com designates 209.85.208.176 as permitted sender) smtp.mailfrom=yosryahmed@google.com; dmarc=pass (policy=reject) header.from=google.com Received: by mail-lj1-f176.google.com with SMTP id 38308e7fff4ca-2b9c0391749so25043841fa.0 for ; Thu, 10 Aug 2023 20:08:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1691723338; x=1692328138; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=G8YBwS2ISUNabVdCBzJa481Mq/UZwGsjfMQseGixYF4=; b=yl5y7atSLvHgslxn5DdrVFFFhDFyeJHAP17+Smr6lD4lKwlVZcIK8cXbuMIZ3WJr/r ZqnHN6HESHmyah2XWJRyDQuMS6mOjgEwOtSyPN9e5zwbjcLC06Y1R/Z5oLNjemjfZ0+u Q10cVSD783Is0uhcV/LPkWnABSXXlvwpY8CZ+m8ErenHw/fzCP0Y0OW8581T+hatckk+ Q1ZyVaSHYNbQZ8HMj0xfNaLHmmImDdSst/GyiZEQ23xeyuCSCOFKo9tcIC84R2MZlfx5 zVHRjNAHoCMVPQZlnECnA+l12Gj0tEeqsvcacUr5AjbJdqtiIDKXXYJcfpD9uOzTDfGV ECLw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691723338; x=1692328138; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=G8YBwS2ISUNabVdCBzJa481Mq/UZwGsjfMQseGixYF4=; b=jByd1qdGtRtwmronWeaaOJXu+MzrzzToUp//4I3xIFLD5WweQnVp7nkBQj/cry3yRy edMexCU5G543J29/EJuKs/zPtflARDx2hUfgLnX8nT0on/57ZqwbAtWSRjKNJPKWyq+K Jl6nlkDbi7h72XQaXt7J3hXvMoWQOUGCqdZVu4xb7KOCLaKGJj4m+qWyXqSitJKeOz9Z PPSrk23gHCMwoadEYTXGsUaO1yxXfeDNFc8wL106CYTvsX7eBW6C5bWX2nKJlC9WJcXY VKFIwKsECL5SM9nVLuPYAZ3fNpwsinWT55pElIxQD/vKcNpTt3nej2bFEajAc7qR++2W TmBw== X-Gm-Message-State: AOJu0YzwNZG6HKBTjcDN4/qwzd2mXGNVqvpTpKraC9I+o+ODS4Iz1SpQ Cwo4B8fsuCly1U8kSZLJzotYaoqMOVkQPCgefAaozQ== X-Google-Smtp-Source: AGHT+IHQPkbTXHw+6XYaWn9vCzZud7FF2o+bd6fiUGfcTHI+FwRMti3zGpdYSaTaDNnAsBra68w15NIqlwjg6tSZ3MU= X-Received: by 2002:a2e:9d88:0:b0:2ba:5ca7:2311 with SMTP id c8-20020a2e9d88000000b002ba5ca72311mr644539ljj.41.1691723337822; Thu, 10 Aug 2023 20:08:57 -0700 (PDT) MIME-Version: 1.0 References: <20230810095652.3905184-1-fengwei.yin@intel.com> <26949c92-95a0-414f-918a-8b8cc11e3e9c@intel.com> <3732dd16-148d-4ac6-8295-86a12f89365b@intel.com> <6cc1654a-460c-474a-864c-04a53ca1ca05@intel.com> In-Reply-To: From: Yosry Ahmed Date: Thu, 10 Aug 2023 20:08:20 -0700 Message-ID: Subject: Re: [PATCH] zswap: don't warn if none swapcache folio is passed to zswap_load To: Yu Zhao Cc: "Yin, Fengwei" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, willy@infradead.org, hannes@cmpxchg.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: pmawgs8jebgwkr7dqf1wr3utqashyeur X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0AF1F2001F X-Rspam-User: X-HE-Tag: 1691723339-670951 X-HE-Meta: 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 LPAPPjdh Zil+tbQY/2K+oEFaXEknJuqf+ovXsOyXIK9NCXe/u4WAjMu4ZrFNgUXYZ8agpRsNWxLeTuvwWqkQHLtDNGtIu2OMAGtMZdRcZIT4N08O7zhnBfpPvYc/ZqIhtO26ihBrxr+I2q3FAA6AlUGIdVNuwXDoTRN4HLi+fzBm5AYlw+UFyiuwmvNBK29IvjpKEicVIKUzrYANH3CbZGqcEFrXF07aiSnexJuvcwuF6eToQfMcdumfdN94shO8TmxOypAUrV+9WqmAHRDLLYlu77s1S9O2PFN4p35HF2CmyOU16y4PfeSLxvtrZ1sdYXCSZgfQlQVvv 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: On Thu, Aug 10, 2023 at 8:03=E2=80=AFPM Yu Zhao wrote: > > On Thu, Aug 10, 2023 at 6:37=E2=80=AFPM Yin, Fengwei wrote: > > > > > > > > On 8/11/2023 7:43 AM, Yu Zhao wrote: > > > On Thu, Aug 10, 2023 at 5:31=E2=80=AFPM Yin, Fengwei wrote: > > >> > > >> > > >> > > >> On 8/11/2023 7:15 AM, Yosry Ahmed wrote: > > >>> On Thu, Aug 10, 2023 at 4:09=E2=80=AFPM Yin, Fengwei wrote: > > >>>> > > >>>> > > >>>> > > >>>> On 8/11/2023 2:44 AM, Yu Zhao wrote: > > >>>>> On Thu, Aug 10, 2023 at 3:58=E2=80=AFAM Yin Fengwei wrote: > > >>>>>> > > >>>>>> With mm-unstable branch, if trigger swap activity and it's possi= ble > > >>>>>> see following warning: > > >>>>>> [ 178.093511][ T651] WARNING: CPU: 2 PID: 651 at mm/zswap.c:13= 87 zswap_load+0x67/0x570 > > >>>>>> [ 178.095155][ T651] Modules linked in: > > >>>>>> [ 178.096103][ T651] CPU: 2 PID: 651 Comm: gmain Not tainted 6= .5.0-rc4-00492-gad3232df3e41 #148 > > >>>>>> [ 178.098372][ T651] Hardware name: QEMU Standard PC (i440FX += PIIX,1996), BIOS 1.14.0-2 04/01/2014 > > >>>>>> [ 178.101114][ T651] RIP: 0010:zswap_load+0x67/0x570 > > >>>>>> [ 178.102359][ T651] Code: a0 78 4b 85 e8 ea db ff ff 48 8b 00= a8 01 0f 84 84 04 00 00 48 89 df e8 d7 db ff ff 48 8b 00 a9 00 00 08 00 0f= 85 c4 > > >>>>>> [ 178.106376][ T651] RSP: 0018:ffffc900011b3760 EFLAGS: 000102= 46 > > >>>>>> [ 178.107675][ T651] RAX: 0017ffffc0080001 RBX: ffffea0004a991= c0 RCX:ffffc900011b37dc > > >>>>>> [ 178.109242][ T651] RDX: 0000000000000000 RSI: 00000000000000= 01 RDI:ffffea0004a991c0 > > >>>>>> [ 178.110916][ T651] RBP: ffffea0004a991c0 R08: 00000000000002= 43 R09:00000000c9a1aafc > > >>>>>> [ 178.112377][ T651] R10: 00000000c9657db3 R11: 000000003c9657= db R12:0000000000014b9c > > >>>>>> [ 178.113698][ T651] R13: ffff88813501e710 R14: ffff88810d5910= 00 R15:0000000000000000 > > >>>>>> [ 178.115008][ T651] FS: 00007fb21a9ff700(0000) GS:ffff88813b= c80000(0000) knlGS:0000000000000000 > > >>>>>> [ 178.116423][ T651] CS: 0010 DS: 0000 ES: 0000 CR0: 00000000= 80050033 > > >>>>>> [ 178.117421][ T651] CR2: 00005632cbfc81f6 CR3: 00000001314500= 02 CR4:0000000000370ee0 > > >>>>>> [ 178.118683][ T651] DR0: 0000000000000000 DR1: 00000000000000= 00 DR2:0000000000000000 > > >>>>>> [ 178.119894][ T651] DR3: 0000000000000000 DR6: 00000000fffe0f= f0 DR7:0000000000000400 > > >>>>>> [ 178.121087][ T651] Call Trace: > > >>>>>> [ 178.121654][ T651] > > >>>>>> [ 178.122109][ T651] ? zswap_load+0x67/0x570 > > >>>>>> [ 178.122658][ T651] ? __warn+0x81/0x170 > > >>>>>> [ 178.123119][ T651] ? zswap_load+0x67/0x570 > > >>>>>> [ 178.123608][ T651] ? report_bug+0x167/0x190 > > >>>>>> [ 178.124150][ T651] ? handle_bug+0x3c/0x70 > > >>>>>> [ 178.124615][ T651] ? exc_invalid_op+0x13/0x60 > > >>>>>> [ 178.125192][ T651] ? asm_exc_invalid_op+0x16/0x20 > > >>>>>> [ 178.125753][ T651] ? zswap_load+0x67/0x570 > > >>>>>> [ 178.126231][ T651] ? lock_acquire+0xbb/0x290 > > >>>>>> [ 178.126745][ T651] ? folio_add_lru+0x40/0x1c0 > > >>>>>> [ 178.127261][ T651] ? find_held_lock+0x2b/0x80 > > >>>>>> [ 178.127776][ T651] swap_readpage+0xc7/0x5c0 > > >>>>>> [ 178.128273][ T651] do_swap_page+0x86d/0xf50 > > >>>>>> [ 178.128770][ T651] ? __pte_offset_map+0x3e/0x290 > > >>>>>> [ 178.129321][ T651] ? __pte_offset_map+0x1c4/0x290 > > >>>>>> [ 178.129883][ T651] __handle_mm_fault+0x6ad/0xca0 > > >>>>>> [ 178.130419][ T651] handle_mm_fault+0x18b/0x410 > > >>>>>> [ 178.130992][ T651] do_user_addr_fault+0x1f1/0x820 > > >>>>>> [ 178.132076][ T651] exc_page_fault+0x63/0x1a0 > > >>>>>> [ 178.132599][ T651] asm_exc_page_fault+0x22/0x30 > > >>>>>> > > >>>>>> It's possible that swap_readpage() is called with none swapcache= folio > > >>>>>> in do_swap_page() and trigger this warning. So we shouldn't assu= me > > >>>>>> zswap_load() always takes swapcache folio. > > >>>>> > > >>>>> Did you use a bdev with QUEUE_FLAG_SYNCHRONOUS? Otherwise it soun= ds > > >>>>> like a bug to me. > > >>>> I hit this warning with zram which has QUEUE_FLAG_SYNCHRONOUS set.= Thanks. > > >>> > > >>> Does it make sense to keep the warning and instead change it to che= ck > > >>> SWP_SYNCHRONOUS_IO as well? Something like: > > >>> > > >>> VM_WARN_ON_ONCE(!folio_test_swapcache(folio) && > > >>> !swap_type_to_swap_info(type)->flags && SWP_SYNCHRONOUS_IO); > > >>> > > >>> Of course this is too ugly, so perhaps we want a helper to check if= a > > >>> swapfile is synchronous. > > >> My understanding was that the WARN here is zswap_load() doesn't expe= ct > > >> a folio not in swapcache. With zram, swap_readpage() must accept the > > >> folio not in swapcache. So this warn should not be there. > > >> > > >> But your comment make more sense to me. I will update the patch not > > >> to remove this WARN. Thanks. > > > > > > That can cause another warning. > > My understanding is that WARN may be wanted by zswap code. > > > > > > > > Please don't overegineer. > > The original patch looks good to me. What Yosry suggested seems not > only overengineered but also can cause a new KCSAN warning. I suppose that can be easily mitigated with data_race(), similar to do_swap_page(). Anyway, I don't feel strongly about it, if you do then we can go with the current patch :) It just feels odd to me to drop a warning from zswap due to an interaction with zram, which should not be happening in practice.