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Subject[PATCH] scsi: storvsc: Fix a panic in the hibernation procedure
Date
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@microsoft.com>
---
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;
}

--
2.19.1
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