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 <decui@xxxxxxxxxxxxx> > --- > 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
