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Wed, 22 Apr 2020 01:28:30 +0000 (UTC) Received: from T590 (ovpn-8-28.pek2.redhat.com [10.72.8.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4818EB3A7E; Wed, 22 Apr 2020 01:28:19 +0000 (UTC) Date: Wed, 22 Apr 2020 09:28:14 +0800 From: Ming Lei To: Dexuan Cui Cc: jejb@linux.ibm.com, martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, hch@lst.de, bvanassche@acm.org, hare@suse.de, mikelley@microsoft.com, longli@microsoft.com, linux-hyperv@vger.kernel.org, wei.liu@kernel.org, sthemmin@microsoft.com, haiyangz@microsoft.com, kys@microsoft.com Subject: Re: [PATCH] scsi: storvsc: Fix a panic in the hibernation procedure Message-ID: <20200422012814.GB299948@T590> References: <1587514644-47058-1-git-send-email-decui@microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1587514644-47058-1-git-send-email-decui@microsoft.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On Tue, Apr 21, 2020 at 05:17:24PM -0700, Dexuan Cui wrote: > During hibernation, the sdevs are suspended automatically in > drivers/scsi/scsi_pm.c before storvsc_suspend(), so after > storvsc_suspend(), there is no disk I/O from the file systems, but there > can still be disk I/O from the kernel space, e.g. disk_check_events() -> > sr_block_check_events() -> cdrom_check_events() can still submit I/O > to the storvsc driver, which causes a paic of NULL pointer dereference, > since storvsc has closed the vmbus channel in storvsc_suspend(): refer > to the below links for more info: > https://lkml.org/lkml/2020/4/10/47 > https://lkml.org/lkml/2020/4/17/1103 > > Fix the panic by blocking/unblocking all the I/O queues properly. > > Note: this patch depends on another patch "scsi: core: Allow the state > change from SDEV_QUIESCE to SDEV_BLOCK" (refer to the second link above). > > Fixes: 56fb10585934 ("scsi: storvsc: Add the support of hibernation") > Signed-off-by: Dexuan Cui > --- > drivers/scsi/storvsc_drv.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c > index fb41636519ee..fd51d2f03778 100644 > --- a/drivers/scsi/storvsc_drv.c > +++ b/drivers/scsi/storvsc_drv.c > @@ -1948,6 +1948,11 @@ static int storvsc_suspend(struct hv_device *hv_dev) > struct storvsc_device *stor_device = hv_get_drvdata(hv_dev); > struct Scsi_Host *host = stor_device->host; > struct hv_host_device *host_dev = shost_priv(host); > + int ret; > + > + ret = scsi_host_block(host); > + if (ret) > + return ret; > > storvsc_wait_to_drain(stor_device); > > @@ -1968,10 +1973,15 @@ static int storvsc_suspend(struct hv_device *hv_dev) > > static int storvsc_resume(struct hv_device *hv_dev) > { > + struct storvsc_device *stor_device = hv_get_drvdata(hv_dev); > + struct Scsi_Host *host = stor_device->host; > int ret; > > ret = storvsc_connect_to_vsp(hv_dev, storvsc_ringbuffer_size, > hv_dev_is_fc(hv_dev)); > + if (!ret) > + ret = scsi_host_unblock(host, SDEV_RUNNING); > + > return ret; > } scsi_host_block() is actually too heavy for just avoiding scsi internal command, which can be done simply by one atomic variable. Not mention scsi_host_block() is implemented too clumsy because nr_luns * synchronize_rcu() are required in scsi_host_block(), which should have been optimized to just one. Also scsi_device_quiesce() is heavy too, still takes 2 synchronize_rcu() for one LUN. That is said SCSI suspend may take (3 * nr_luns) sysnchronize_rcu() in case that the HBA's suspend handler needs scsi_host_block(). Thanks, Ming