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[23.128.96.18]) by mx.google.com with ESMTP id k5si3031156ejc.134.2021.03.11.18.10.14; Thu, 11 Mar 2021 18:10:36 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=oh8MxH0r; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229636AbhCLCJJ (ORCPT + 99 others); Thu, 11 Mar 2021 21:09:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40802 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229470AbhCLCIj (ORCPT ); Thu, 11 Mar 2021 21:08:39 -0500 Received: from mail-pg1-x533.google.com (mail-pg1-x533.google.com [IPv6:2607:f8b0:4864:20::533]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63F2CC061574; Thu, 11 Mar 2021 18:08:39 -0800 (PST) Received: by mail-pg1-x533.google.com with SMTP id t26so14862803pgv.3; Thu, 11 Mar 2021 18:08:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=79YGAxuRyjMyQxyWZDF0TDTD3u6wj5U3ba9TjFbFALE=; b=oh8MxH0rBZ4t/PYi7xql3NLChmO2awCHSlfRylSHYGzVEWArBCmCnPnwCRZuGcxWex +AM+/cg/AUJYzzsuGeOUlH2xz/oX7XIWnOht02gJm0Si1bwltVznkBJ5q0guii/cxyPh xxQNJTQ5W+nj6WYgyTJWDnZpEZRPwOvV4s0Ji2VbMXBqAP07WalbkMxUzt4HMX1izwO5 EgO1jx8XafdOgjAEp5jKPAVcyioI33P3HEaorhUVt0u1jkFl6ylai062QYqSLAtmShcI OH6hseSjVBBvgeuMAminZ42nYpKG2aYxog1Wr2sRkSVxDJXdX7Ypz8MCvjFpzsWx1xiS NfYw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=79YGAxuRyjMyQxyWZDF0TDTD3u6wj5U3ba9TjFbFALE=; b=SGO2C/yYzKVhQOe4Q8NwRe592LSE6tGuzCe9ElDCWsS7rn816I+j6y36wd+EBaLafB /kJNJBBvagfAKrPNxD2q+VOfY5DbjLPxb/+uX/Vea7Q4N5tQ/u+AbAbfkMLzHqf9jq6R zvWFU0VNgkM5eB00qBVLkORA4rjKQmz7AOBGyZc/cLvj8muEUOA0vdlpFJN9kZ41b9+X tcBgvtCHOgBjN7Emifmri+D54HyFA8CZt4f0JMlHz0RSI7Hafi1eq1TSwbk6rOBixVIT ncfwDiO2w1phjamV501cjSNglBrMvz6N+fI8kUB0Y5GSC3ZL7kH+NGV+43CdvCgxDGPi fmag== X-Gm-Message-State: AOAM531Ge40mkmi6X2c5UAkEHK+diY1yULUBZbemONNhTjiyQIMJekw6 XrCmgoM7hNqejhzowMqty4k= X-Received: by 2002:a62:43:0:b029:1cd:2de2:5a24 with SMTP id 64-20020a6200430000b02901cd2de25a24mr9972822pfa.27.1615514918709; Thu, 11 Mar 2021 18:08:38 -0800 (PST) Received: from google.com ([2620:15c:211:201:64cb:74c7:f2c:e5e0]) by smtp.gmail.com with ESMTPSA id r16sm3646887pfq.211.2021.03.11.18.08.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Mar 2021 18:08:37 -0800 (PST) Sender: Minchan Kim Date: Thu, 11 Mar 2021 18:08:35 -0800 From: Minchan Kim To: Luis Chamberlain Cc: ngupta@vflare.org, sergey.senozhatsky.work@gmail.com, axboe@kernel.dk, mbenes@suse.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] zram: fix crashes due to use of cpu hotplug multistate Message-ID: References: <20210306022035.11266-1-mcgrof@kernel.org> <20210306022035.11266-2-mcgrof@kernel.org> <20210310131115.GQ4332@42.do-not-panic.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210310131115.GQ4332@42.do-not-panic.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 10, 2021 at 01:11:15PM +0000, Luis Chamberlain wrote: > On Mon, Mar 08, 2021 at 06:55:30PM -0800, Minchan Kim wrote: > > On Sat, Mar 06, 2021 at 02:20:34AM +0000, Luis Chamberlain wrote: > > > The zram driver makes use of cpu hotplug multistate support, > > > whereby it associates a zram compression stream per CPU. To > > > support CPU hotplug multistate a callback enabled to allow > > > the driver to do what it needs when a CPU hotplugs. > > > > > > It is however currently possible to end up removing the > > > zram driver callback prior to removing the zram compression > > > streams per CPU. This would leave these compression streams > > > hanging. > > > > > > We need to fix ordering for driver load / removal, zram > > > device additions, in light of the driver's use of cpu > > > hotplug multistate. Since the zram driver exposes many > > > sysfs attribute which can also muck with the comrpession > > > streams this also means we can hit page faults today easily. > > > > Hi Luis, > > > > First of all, thanks for reporting the ancient bugs. > > > > Looks like you found several bugs and I am trying to digest them > > from your description to understand more clear. I need to ask > > stupid questions, first. > > > > If I understand correctly, bugs you found were related to module > > unloading race while the zram are still working. > > If so, couldn't we fix the bug like this(it's not a perfect > > patch but just wanted to show close module unloading race)? > > (I might miss other pieces here. Let me know. Thanks!) > > > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > > index a711a2e2a794..646ae9e0b710 100644 > > --- a/drivers/block/zram/zram_drv.c > > +++ b/drivers/block/zram/zram_drv.c > > @@ -1696,6 +1696,8 @@ static void zram_reset_device(struct zram *zram) > > return; > > } > > > > + module_put(THIS_MODULE); > > + > > comp = zram->comp; > > disksize = zram->disksize; > > zram->disksize = 0; > > @@ -1744,13 +1746,19 @@ static ssize_t disksize_store(struct device *dev, > > goto out_free_meta; > > } > > > > + if (!try_module_get(THIS_MODULE)) > > + goto out_free_zcomp; > > + > > zram->comp = comp; > > zram->disksize = disksize; > > + > > set_capacity_and_notify(zram->disk, zram->disksize >> SECTOR_SHIFT); > > up_write(&zram->init_lock); > > > > return len; > > > > +out_free_zcomp: > > + zcomp_destroy(comp); > > out_free_meta: > > zram_meta_free(zram, disksize); > > out_unlock: > > This still allows for a crash on the driver by running the zram02.sh script twice. > > Mar 09 14:52:19 kdevops-blktests-block-dev kernel: zram0: detected capacity change from 209715200 to 0 > Mar 09 14:52:19 kdevops-blktests-block-dev kernel: BUG: unable to handle page fault for address: ffffba7db7904008 > Mar 09 14:52:19 kdevops-blktests-block-dev kernel: #PF: supervisor read access in kernel mode > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: #PF: error_code(0x0000) - not-present page > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: PGD 100000067 P4D 100000067 PUD 100311067 PMD 14cd2f067 PTE 0 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: Oops: 0000 [#1] SMP NOPTI > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: CPU: 0 PID: 2137 Comm: zram02.sh Tainted: G E 5.12.0-rc1-next-20210304+ #4 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RIP: 0010:zram_free_page+0x1b/0xf0 [zram] > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: Code: 1f 44 00 00 48 89 c8 c3 0f 1f 80 00 00 00 00 0f 1f 44 00 00 41 54 49 89 f4 55 89 f5 53 48 8b 17 48 c1 e5 04 48 89 f> > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RSP:0018:ffffba7d808f3d88 EFLAGS: 00010286 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RAX: 0000000000000000 RBX: ffff9eee5317d200 RCX: 0000000000000000 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RDX: ffffba7db7904000 RSI: 0000000000000000 RDI: ffff9eee5317d200 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RBP: 0000000000000000 R08: 00000008f78bb1d3 R09: 0000000000000000 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: R10: 0000000000000008 R11: 0000000000000000 R12: 0000000000000000 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: R13: ffff9eee53d4cb00 R14: ffff9eee5317d220 R15: ffff9eee70508b80 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: FS: 00007f4bb1482580(0000) GS:ffff9eef77c00000(0000) knlGS:0000000000000000 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: CR2: ffffba7db7904008 CR3: 0000000107e9c000 CR4: 0000000000350ef0 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: Call Trace: > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: zram_reset_device+0xe9/0x150 [zram] > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: reset_store+0x9a/0x100 [zram] > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: kernfs_fop_write_iter+0x124/0x1b0 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: new_sync_write+0x11c/0x1b0 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: vfs_write+0x1c2/0x260 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: ksys_write+0x5f/0xe0 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: do_syscall_64+0x33/0x80 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: entry_SYSCALL_64_after_hwframe+0x44/0xae > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RIP: 0033:0x7f4bb13aaf33 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: Code: 8b 15 61 ef 0c 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 64 8b 04 25 18 00 > 00 00 85 c0 75 14 b8 01 00 0> > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RSP: 002b:00007ffce0090d88 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RAX: ffffffffffffffda RBX: 000055a17c4a14b0 RCX: 00007f4bb13aaf33 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RDX: 0000000000000002 RSI: 000055a17c4a14b0 RDI: 0000000000000001 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: RBP: 0000000000000002 R08: 000055a17c48a1d0 R09: 0000000000000000 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: R10: 000055a17c48a1d1 R11: 0000000000000246 R12: 0000000000000001 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: R13: 0000000000000002 R14: 7fffffffffffffff R15: 0000000000000000 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: Modules linked in: zram(E) zsmalloc(E) xfs(E) crct10dif_pclmul(E) crc32_pclmul(E) ghash_clmulni_intel(E) joydev(E) evdev(> > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: zram0: detected capacity change from 0 to 209715200 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: CR2: ffffba7db7904008 > Mar 09 14:52:20 kdevops-blktests-block-dev kernel: ---[ end trace 534ee1d0b880dd90 ]--- > > I can try to modify it to include second patch first, as that is > required. There are two separate bugs here. Or was your goalt to > try to address both with only one patch? I am trying to understand problem first.