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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AF69BC43219 for ; Fri, 11 Nov 2022 00:48:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230505AbiKKAsm (ORCPT ); Thu, 10 Nov 2022 19:48:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230208AbiKKAsi (ORCPT ); Thu, 10 Nov 2022 19:48:38 -0500 Received: from mail-pf1-x430.google.com (mail-pf1-x430.google.com [IPv6:2607:f8b0:4864:20::430]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8E0B1E725 for ; Thu, 10 Nov 2022 16:48:37 -0800 (PST) Received: by mail-pf1-x430.google.com with SMTP id i3so3531013pfc.11 for ; Thu, 10 Nov 2022 16:48:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=/gUNRy1qZIXrqUZUL7883/f/GJegibYfXZQZVngW38U=; b=VWZwrH2WTLZH7q/x1ZgpdvYSrGqwsN5f7i9ypcQ7UreI7sa/e03yNK6qv9VxqDlXP8 i04ZhlEljAEqFDY6vjaYs/QXE3J3167rQ2D69YQqoO8AcyVoep415lPw40kShPC8NBdV 9bzPkkL603xzDjwINJOebgWujA4I8bQIIWYOA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=/gUNRy1qZIXrqUZUL7883/f/GJegibYfXZQZVngW38U=; b=qCPwe1hT3uzgFutGN+IwljCbKlb4Cf790Z+XKmRuqLzIwHtfQBGC2TuBz3Se6dTRYw sUeWYfgztIvRLaEjVwaU2k+nHDsJLQYOOKeqCSuv5/CaLQFTkeosOpYS5S+3OUpgVqRh zuz6DXBaFuQ1H89hHrPJ+0+tW3rejNzZbSzwf+VqHW8JCZVu8p8vwkyV5hKNy+GBCH+y 9EAHkNpXPccbdIYkY+zq/Z23lGVc3KNa+JwDwbHqF95wgMz7Nj+busw/gp/KNxeVmLae 4pLPgIUmMh1ujK0brNArO1jTqSo+FuJ5o/sQcTNRVofh7sj89rQksoXtWLDmflCJk6tb fvdA== X-Gm-Message-State: ACrzQf0WzEFepZqxoItlawlHdDKXcf0q6TYXoLb4Bb99cMHXIX/+IZqX xQ2Mpt9szfUBzCGs/IzhzyVR9Q== X-Google-Smtp-Source: AMsMyM7sIWgS/0TfYwBT7X/dzMu66eUOL/4N1tpn2UCyic5dZmo1cMUhDUlzUKuzT+rqzDYvi7knxQ== X-Received: by 2002:a63:fc14:0:b0:43c:2e57:97df with SMTP id j20-20020a63fc14000000b0043c2e5797dfmr3852168pgi.189.1668127717205; Thu, 10 Nov 2022 16:48:37 -0800 (PST) Received: from google.com ([240f:75:7537:3187:8d55:c60d:579d:741c]) by smtp.gmail.com with ESMTPSA id g6-20020a632006000000b004388ba7e5a9sm221005pgg.49.2022.11.10.16.48.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Nov 2022 16:48:36 -0800 (PST) Date: Fri, 11 Nov 2022 09:48:31 +0900 From: Sergey Senozhatsky To: Martin Doucha Cc: Minchan Kim , Petr Vorel , ltp@lists.linux.it, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Nitin Gupta , Sergey Senozhatsky , Jens Axboe , OGAWA Hirofumi , Yang Xu Subject: Re: [PATCH 0/1] Possible bug in zram on ppc64le on vfat Message-ID: References: <20221107191136.18048-1-pvorel@suse.cz> <3ac740c0-954b-5e68-b413-0adc7bc5a2b5@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3ac740c0-954b-5e68-b413-0adc7bc5a2b5@suse.cz> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (22/11/10 15:29), Martin Doucha wrote: > New version of LTP test zram01 found a sysfile issue with zram devices > mounted using VFAT filesystem. When when all available space is filled, e.g. > by `dd if=/dev/zero of=/mnt/zram0/file`, the corresponding sysfile > /sys/block/zram0/mm_stat will report that the compressed data size on the > device is 0 and total memory usage is also 0. LTP test zram01 uses these > values to calculate compression ratio, which results in division by zero. > > The issue is specific to PPC64LE architecture and the VFAT filesystem. No > other tested filesystem has this issue and I could not reproduce it on other > archs (s390 not tested). The issue appears randomly about every 3 test runs > on SLE-15SP2 and 15SP3 (kernel 5.3). It appears less frequently on SLE-12SP5 > (kernel 4.12). Other SLE version were not tested with the new test version > yet. The previous version of the test did not check the VFAT filesystem on > zram devices. Whoooaa... > I've tried to debug the issue and collected some interesting data (all > values come from zram device with 25M size limit and zstd compression > algorithm): > - mm_stat values are correct after mkfs.vfat: > 65536 220 65536 26214400 65536 0 0 0 > > - mm_stat values stay correct after mount: > 65536 220 65536 26214400 65536 0 0 0 > > - the bug is triggered by filling the filesystem to capacity (using dd): > 4194304 0 0 26214400 327680 64 0 0 Can you try using /dev/urandom for dd, not /dev/zero? Do you still see zeroes in sysfs output or some random values?