Cc'ing lee.
On 10/5/21 11:31 PM, Mike Christie wrote:
> This fixes a regression added with:
>
> commit f0f82e2476f6 ("scsi: core: Fix capacity set to zero after
> offlinining device")
>
> The problem is that after iSCSI recovery, iscsid will call into the kernel
> to set the dev's state to running, and with that patch we now call
> scsi_rescan_device with the state_mutex held. If the scsi error handler
> thread is just starting to test the device in scsi_send_eh_cmnd then it's
> going to try to grab the state_mutex.
>
> We are then stuck, because when scsi_rescan_device tries to send its IO
> scsi_queue_rq calls -> scsi_host_queue_ready -> scsi_host_in_recovery
> will return true (the host state is still in recovery) and IO will just be
> requeued. scsi_send_eh_cmnd will then never be able to grab the
> state_mutex to finish error handling.
>
> This just moves the scsi_rescan_device call to after we drop the
> state_mutex.
I want to maybe nak my own patch. There is still a problem where if one
of the rescan IOs hits an issue then userspace is stuck waiting for
however long it takes to perform recovery. For iscsid, this will cause
problems because it sets the device state from its main thread. So
while scsi_rescan_device is hung then iscsid can't do anything for
any session.
I think we either want to:
1. Do the patch below, but Lee will need to change iscsid so it sets
the dev state from a worker thread.
2. Have the kernel kick off the rescan from a workqueue. This seems
easiest but I'm not sure if it will cause issues for lijinlin's use
case.
>
> Fixes: f0f82e2476f6 ("scsi: core: Fix capacity set to zero after
> offlinining device")
> Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
> ---
> drivers/scsi/scsi_sysfs.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 86793259e541..5b63407c3a3f 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -788,6 +788,7 @@ store_state_field(struct device *dev, struct device_attribute *attr,
> int i, ret;
> struct scsi_device *sdev = to_scsi_device(dev);
> enum scsi_device_state state = 0;
> + bool rescan_dev = false;
>
> for (i = 0; i < ARRAY_SIZE(sdev_states); i++) {
> const int len = strlen(sdev_states[i].name);
> @@ -817,10 +818,13 @@ store_state_field(struct device *dev, struct device_attribute *attr,
> */
> if (ret == 0 && state == SDEV_RUNNING) {
> blk_mq_run_hw_queues(sdev->request_queue, true);
> - scsi_rescan_device(dev);
> + rescan_dev = true;
> }
> mutex_unlock(&sdev->state_mutex);
>
> + if (rescan_dev)
> + scsi_rescan_device(dev);
> +
> return ret == 0 ? count : -EINVAL;
> }
>
>
