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

[Hannes Reinecke <hare@suse.de>]

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?
Weird. We'll get notified about this eventually anyway (aborting
I/Os etc).
I'd be more interested to get notified if the device becomes
_available_ again, ie when entering RUNNING state. That's really
hard to figure out without polling.

Care to add the 'change_evt' thing to the SDEV_RUNNING case
statement, too?

Or am I missing something?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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