On 02/11/2016 09:33 PM, Ewan Milne wrote:
> On Mon, 2016-02-08 at 15:34 +0100, Hannes Reinecke wrote:
>> Add an 'access_state' attribute to struct scsi_device to
>> display the asymmetric LUN access state.
>>
>> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
>> Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
>> ---
>> drivers/scsi/scsi_scan.c | 1 +
>> drivers/scsi/scsi_sysfs.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++
>> include/scsi/scsi_device.h | 1 +
>> include/scsi/scsi_proto.h | 13 ++++++++++++
>> 4 files changed, 64 insertions(+)
>>
>> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
>> index 97074c9..5bf3945 100644
>> --- a/drivers/scsi/scsi_scan.c
>> +++ b/drivers/scsi/scsi_scan.c
>> @@ -231,6 +231,7 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
>> sdev->lun = lun;
>> sdev->channel = starget->channel;
>> sdev->sdev_state = SDEV_CREATED;
>> + sdev->access_state = SCSI_ACCESS_STATE_UNKNOWN;
>> INIT_LIST_HEAD(&sdev->siblings);
>> INIT_LIST_HEAD(&sdev->same_target_siblings);
>> INIT_LIST_HEAD(&sdev->cmd_list);
>> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
>> index 4f18a85..8d154ed 100644
>> --- a/drivers/scsi/scsi_sysfs.c
>> +++ b/drivers/scsi/scsi_sysfs.c
>> @@ -81,6 +81,34 @@ const char *scsi_host_state_name(enum scsi_host_state state)
>> return name;
>> }
>>
>> +static const struct {
>> + enum scsi_access_state value;
>> + char *name;
>> +} sdev_access_states[] = {
>> + { SCSI_ACCESS_STATE_OPTIMAL, "active/optimized" },
>> + { SCSI_ACCESS_STATE_ACTIVE, "active/non-optimized" },
>> + { SCSI_ACCESS_STATE_STANDBY, "standby" },
>> + { SCSI_ACCESS_STATE_UNAVAILABLE, "unavailable" },
>> + { SCSI_ACCESS_STATE_LBA, "lba-dependent" },
>> + { SCSI_ACCESS_STATE_OFFLINE, "offline" },
>> + { SCSI_ACCESS_STATE_TRANSITIONING, "transitioning" },
>> + { SCSI_ACCESS_STATE_UNKNOWN, "unknown" },
>> +};
>> +
>> +const char *scsi_access_state_name(enum scsi_access_state state)
>> +{
>> + int i;
>> + char *name = NULL;
>> +
>> + for (i = 0; i < ARRAY_SIZE(sdev_access_states); i++) {
>> + if (sdev_access_states[i].value == state) {
>> + name = sdev_access_states[i].name;
>> + break;
>> + }
>> + }
>> + return name;
>> +}
>> +
>> static int check_set(unsigned long long *val, char *src)
>> {
>> char *last;
>> @@ -973,6 +1001,26 @@ sdev_store_dh_state(struct device *dev, struct device_attribute *attr,
>>
>> static DEVICE_ATTR(dh_state, S_IRUGO | S_IWUSR, sdev_show_dh_state,
>> sdev_store_dh_state);
>> +
>> +static ssize_t
>> +sdev_show_access_state(struct device *dev,
>> + struct device_attribute *attr,
>> + char *buf)
>> +{
>> + struct scsi_device *sdev = to_scsi_device(dev);
>> + enum scsi_access_state access_state;
>> + bool pref = false;
>> +
>> + if (sdev->access_state & SCSI_ACCESS_STATE_PREFERRED)
>> + pref = true;
>> +
>> + access_state = (sdev->access_state & SCSI_ACCESS_STATE_MASK);
>
> I personally think it is a mistake to stick an extra bit in the
> top of a variable declared as an enum like this. It opens up
> the possibility of subtle bugs if someone changes the code in
> the future and does not take care to preserve your extra bit.
>
But I felt even more stupid adding yet another bit to the
scsi_device structure ...
>> +
>> + return snprintf(buf, 32, "%s%s\n",
>> + scsi_access_state_name(access_state),
>> + pref ? " preferred" : "");
>> +}
>> +static DEVICE_ATTR(access_state, S_IRUGO, sdev_show_access_state, NULL);
>> #endif
>>
>> static ssize_t
>> @@ -1047,6 +1095,7 @@ static struct attribute *scsi_sdev_attrs[] = {
>> &dev_attr_wwid.attr,
>> #ifdef CONFIG_SCSI_DH
>> &dev_attr_dh_state.attr,
>> + &dev_attr_access_state.attr,
>> #endif
>> &dev_attr_queue_ramp_up_period.attr,
>> REF_EVT(media_change),
>> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
>> index 4af2b24..af16a0d 100644
>> --- a/include/scsi/scsi_device.h
>> +++ b/include/scsi/scsi_device.h
>> @@ -201,6 +201,7 @@ struct scsi_device {
>> struct scsi_device_handler *handler;
>> void *handler_data;
>>
>> + enum scsi_access_state access_state;
>> enum scsi_device_state sdev_state;
>> unsigned long sdev_data[0];
>> } __attribute__((aligned(sizeof(unsigned long))));
>> diff --git a/include/scsi/scsi_proto.h b/include/scsi/scsi_proto.h
>> index a9fbf1b..80e85e7 100644
>> --- a/include/scsi/scsi_proto.h
>> +++ b/include/scsi/scsi_proto.h
>> @@ -277,5 +277,18 @@ struct scsi_lun {
>> __u8 scsi_lun[8];
>> };
>>
>> +/* SPC asymmetric access states */
>> +enum scsi_access_state {
>> + SCSI_ACCESS_STATE_OPTIMAL = 0,
>> + SCSI_ACCESS_STATE_ACTIVE,
>> + SCSI_ACCESS_STATE_STANDBY,
>> + SCSI_ACCESS_STATE_UNAVAILABLE,
>> + SCSI_ACCESS_STATE_LBA,
>> + SCSI_ACCESS_STATE_OFFLINE = 0xe,
>> + SCSI_ACCESS_STATE_TRANSITIONING = 0xf,
>> + SCSI_ACCESS_STATE_UNKNOWN = 0x70,
>> +};
>
> Given that these values are defined by the T10 spec and their values
> matter, I think it would be prudent to assign specific values to each
> enum constant, rather than just let the compiler do that.
>
Fair point.
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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