cciss: Add usage_count attribute to each logical drive in /sys

Add usage_count attribute to each logical drive at
/sys/devices/<dev>/ccissX/cXdY/usage_count for controller X,
logical drive Y.  The usage count is the number of times
the device has currently been opened.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-pci-devices-cciss b/Documentation/ABI/testing/sysfs-bus-pci-devices-cciss
index 8d0260256168..4f29e5f1ebfa 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-devices-cciss
+++ b/Documentation/ABI/testing/sysfs-bus-pci-devices-cciss
@@ -52,3 +52,10 @@ Kernel Version: 2.6.31
 Contact:        iss_storagedev@hp.com
 Description:    Displays the RAID level of logical drive Y of
                 controller X.
+
+Where:          /sys/bus/pci/devices/<dev>/ccissX/cXdY/usage_count
+Date:           August 2009
+Kernel Version: 2.6.31
+Contact:        iss_storagedev@hp.com
+Description:    Displays the usage count (number of opens) of logical drive Y
+                of controller X.
diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 063e8b0834da..b808e9287b73 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -626,6 +626,25 @@ static ssize_t cciss_show_raid_level(struct device *dev,
 }
 DEVICE_ATTR(raid_level, S_IRUGO, cciss_show_raid_level, NULL);
 
+static ssize_t cciss_show_usage_count(struct device *dev,
+                                      struct device_attribute *attr, char *buf)
+{
+        drive_info_struct *drv = dev_get_drvdata(dev);
+        struct ctlr_info *h = to_hba(drv->dev->parent);
+        unsigned long flags;
+        int count;
+
+        spin_lock_irqsave(CCISS_LOCK(h->ctlr), flags);
+        if (h->busy_configuring) {
+                spin_unlock_irqrestore(CCISS_LOCK(h->ctlr), flags);
+                return -EBUSY;
+        }
+        count = drv->usage_count;
+        spin_unlock_irqrestore(CCISS_LOCK(h->ctlr), flags);
+        return snprintf(buf, 20, "%d\n", count);
+}
+DEVICE_ATTR(usage_count, S_IRUGO, cciss_show_usage_count, NULL);
+
 static struct attribute *cciss_host_attrs[] = {
         &dev_attr_rescan.attr,
         NULL
@@ -653,6 +672,7 @@ static struct attribute *cciss_dev_attrs[] = {
         &dev_attr_rev.attr,
         &dev_attr_lunid.attr,
         &dev_attr_raid_level.attr,
+        &dev_attr_usage_count.attr,
         NULL
 };