Re: [PATCH 4/4] SCSI: send KOBJ_CHANGE when device is set to running v2

[Mike Christie <michaelc@cs.wisc.edu>]

On 05/21/2012 10:32 AM, Mike Christie wrote:
> On 05/21/2012 06:45 AM, Hannes Reinecke wrote:
>> On 05/18/2012 06:56 AM, michaelc@cs.wisc.edu wrote:
>>> From: Mike Christie <michaelc@cs.wisc.edu>
>>>
>>> If a device goes offline while the device is opened then closed
>>> while it is still offline, udev will remove the /dev/disk/by-id
>>> link. If the device comes back and is set to running, userspace
>>> is not notified, and the by-id link will not get remade.
>>>
>>> This patch has scsi-ml send a KOBJ_CHANGE event so tools like udev
>>> will know that it can being to use the device again. With this patch
>>> udev see the KOBJ_CHANGE event and will reprobe the device and recreate
>>> a /dev/disk/by-id link.
>>>
>>> v2
>>> - Added SDEV_EVT_STATE_RUNNING evt type.
>>>
>>> Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
>>> ---
>>>  drivers/scsi/scsi_lib.c    |    9 +++++++++
>>>  include/scsi/scsi_device.h |    2 ++
>>>  2 files changed, 11 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>>> index d15b243..b54030d 100644
>>> --- a/drivers/scsi/scsi_lib.c
>>> +++ b/drivers/scsi/scsi_lib.c
>>> @@ -2061,6 +2061,7 @@ int
>>>  scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
>>>  {
>>>  	enum scsi_device_state oldstate = sdev->sdev_state;
>>> +	int change_evt = 0;
>>>  
>>>  	if (state == oldstate)
>>>  		return 0;
>>> @@ -2079,6 +2080,11 @@ scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
>>>  		switch (oldstate) {
>>>  		case SDEV_OFFLINE:
>>>  		case SDEV_TRANSPORT_OFFLINE:
>>> +			/*
>>> +			 * Notify userspace we can accept IO by sending
>>> +			 * change event.
>>> +			 */
>>> +			change_evt = 1;
>>>  		case SDEV_QUIESCE:
>>>  		case SDEV_BLOCK:
>>>  		case SDEV_CREATED:
>>> @@ -2160,6 +2166,8 @@ scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
>>>  
>>>  	}
>>>  	sdev->sdev_state = state;
>>> +	if (change_evt)
>>> +		sdev_evt_send_simple(sdev, SDEV_EVT_STATE_RUNNING, GFP_ATOMIC);
>>>  	return 0;
>>>  
>>>   illegal:
>>> @@ -2283,6 +2291,7 @@ struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
>>>  	/* evt_type-specific initialization, if any */
>>>  	switch (evt_type) {
>>>  	case SDEV_EVT_MEDIA_CHANGE:
>>> +	case SDEV_EVT_STATE_RUNNING:
>>>  	default:
>>>  		/* do nothing */
>>>  		break;
>> Hmm. So we're only getting notified if the device switched to OFFLINE?
> 
> No from one of the offlines to running.
> 

I think I know what happened. Maybe you did not reivew all the patches
at the same time. With all patches in the set applied we have this:


scsi_device_set_state()
......

        case SDEV_RUNNING:	<- so we are going into running
                switch (oldstate) {
                case SDEV_OFFLINE:    <- we were in one of the offlines
                case SDEV_TRANSPORT_OFFLINE:
                        /*
                         * Notify userspace we can accept IO by sending
                         * change event.
                         */
                        change_evt = 1;   <- so we send evt for *offline
to running transistions