s390/cio: fix ccw_device_start_timeout API

There are cases a device driver can't start IO because the device is
currently in use by cio. In this case the device driver is notified
when the device is usable again.

Using ccw_device_start_timeout we would set the timeout (and change
an existing timeout) before we test for internal usage. Worst case
this could lead to an unexpected timer deletion.

Fix this by setting the timeout after we test for internal usage.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/device_ops.c

@@ -159,7 +159,7 @@ int ccw_device_clear(struct ccw_device *cdev, unsigned long intparm)
 }
 
 /**
- * ccw_device_start_key() - start a s390 channel program with key
+ * ccw_device_start_timeout_key() - start a s390 channel program with timeout and key
  * @cdev: target ccw device
  * @cpa: logical start address of channel program
  * @intparm: user specific interruption parameter; will be presented back to
@@ -170,10 +170,15 @@ int ccw_device_clear(struct ccw_device *cdev, unsigned long intparm)
  * @key: storage key to be used for the I/O
  * @flags: additional flags; defines the action to be performed for I/O
  *	   processing.
+ * @expires: timeout value in jiffies
  *
  * Start a S/390 channel program. When the interrupt arrives, the
  * IRQ handler is called, either immediately, delayed (dev-end missing,
  * or sense required) or never (no IRQ handler registered).
+ * This function notifies the device driver if the channel program has not
+ * completed during the time specified by @expires. If a timeout occurs, the
+ * channel program is terminated via xsch, hsch or csch, and the device's
+ * interrupt handler will be called with an irb containing ERR_PTR(-%ETIMEDOUT).
  * Returns:
  *  %0, if the operation was successful;
  *  -%EBUSY, if the device is busy, or status pending;
@@ -182,9 +187,9 @@ int ccw_device_clear(struct ccw_device *cdev, unsigned long intparm)
  * Context:
  *  Interrupts disabled, ccw device lock held
  */
-int ccw_device_start_key(struct ccw_device *cdev, struct ccw1 *cpa,
-			 unsigned long intparm, __u8 lpm, __u8 key,
-			 unsigned long flags)
+int ccw_device_start_timeout_key(struct ccw_device *cdev, struct ccw1 *cpa,
+				 unsigned long intparm, __u8 lpm, __u8 key,
+				 unsigned long flags, int expires)
 {
 	struct subchannel *sch;
 	int ret;
@@ -224,6 +229,8 @@ int ccw_device_start_key(struct ccw_device *cdev, struct ccw1 *cpa,
 	switch (ret) {
 	case 0:
 		cdev->private->intparm = intparm;
+		if (expires)
+			ccw_device_set_timeout(cdev, expires);
 		break;
 	case -EACCES:
 	case -ENODEV:
@@ -234,7 +241,7 @@ int ccw_device_start_key(struct ccw_device *cdev, struct ccw1 *cpa,
 }
 
 /**
- * ccw_device_start_timeout_key() - start a s390 channel program with timeout and key
+ * ccw_device_start_key() - start a s390 channel program with key
  * @cdev: target ccw device
  * @cpa: logical start address of channel program
  * @intparm: user specific interruption parameter; will be presented back to
@@ -245,15 +252,10 @@ int ccw_device_start_key(struct ccw_device *cdev, struct ccw1 *cpa,
  * @key: storage key to be used for the I/O
  * @flags: additional flags; defines the action to be performed for I/O
  *	   processing.
- * @expires: timeout value in jiffies
  *
  * Start a S/390 channel program. When the interrupt arrives, the
  * IRQ handler is called, either immediately, delayed (dev-end missing,
  * or sense required) or never (no IRQ handler registered).
- * This function notifies the device driver if the channel program has not
- * completed during the time specified by @expires. If a timeout occurs, the
- * channel program is terminated via xsch, hsch or csch, and the device's
- * interrupt handler will be called with an irb containing ERR_PTR(-%ETIMEDOUT).
  * Returns:
  *  %0, if the operation was successful;
  *  -%EBUSY, if the device is busy, or status pending;
@@ -262,19 +264,12 @@ int ccw_device_start_key(struct ccw_device *cdev, struct ccw1 *cpa,
  * Context:
  *  Interrupts disabled, ccw device lock held
  */
-int ccw_device_start_timeout_key(struct ccw_device *cdev, struct ccw1 *cpa,
-				 unsigned long intparm, __u8 lpm, __u8 key,
-				 unsigned long flags, int expires)
+int ccw_device_start_key(struct ccw_device *cdev, struct ccw1 *cpa,
+			 unsigned long intparm, __u8 lpm, __u8 key,
+			 unsigned long flags)
 {
-	int ret;
-
-	if (!cdev)
-		return -ENODEV;
-	ccw_device_set_timeout(cdev, expires);
-	ret = ccw_device_start_key(cdev, cpa, intparm, lpm, key, flags);
-	if (ret != 0)
-		ccw_device_set_timeout(cdev, 0);
-	return ret;
+	return ccw_device_start_timeout_key(cdev, cpa, intparm, lpm, key,
+					    flags, 0);
 }
 
 /**
@@ -489,18 +484,20 @@ void ccw_device_get_id(struct ccw_device *cdev, struct ccw_dev_id *dev_id)
 EXPORT_SYMBOL(ccw_device_get_id);
 
 /**
- * ccw_device_tm_start_key() - perform start function
+ * ccw_device_tm_start_timeout_key() - perform start function
  * @cdev: ccw device on which to perform the start function
  * @tcw: transport-command word to be started
  * @intparm: user defined parameter to be passed to the interrupt handler
  * @lpm: mask of paths to use
  * @key: storage key to use for storage access
+ * @expires: time span in jiffies after which to abort request
  *
  * Start the tcw on the given ccw device. Return zero on success, non-zero
  * otherwise.
  */
-int ccw_device_tm_start_key(struct ccw_device *cdev, struct tcw *tcw,
-			    unsigned long intparm, u8 lpm, u8 key)
+int ccw_device_tm_start_timeout_key(struct ccw_device *cdev, struct tcw *tcw,
+				    unsigned long intparm, u8 lpm, u8 key,
+				    int expires)
 {
 	struct subchannel *sch;
 	int rc;
@@ -527,37 +524,32 @@ int ccw_device_tm_start_key(struct ccw_device *cdev, struct tcw *tcw,
 			return -EACCES;
 	}
 	rc = cio_tm_start_key(sch, tcw, lpm, key);
-	if (rc == 0)
+	if (rc == 0) {
 		cdev->private->intparm = intparm;
+		if (expires)
+			ccw_device_set_timeout(cdev, expires);
+	}
 	return rc;
 }
-EXPORT_SYMBOL(ccw_device_tm_start_key);
+EXPORT_SYMBOL(ccw_device_tm_start_timeout_key);
 
 /**
- * ccw_device_tm_start_timeout_key() - perform start function
+ * ccw_device_tm_start_key() - perform start function
  * @cdev: ccw device on which to perform the start function
  * @tcw: transport-command word to be started
  * @intparm: user defined parameter to be passed to the interrupt handler
  * @lpm: mask of paths to use
  * @key: storage key to use for storage access
- * @expires: time span in jiffies after which to abort request
  *
  * Start the tcw on the given ccw device. Return zero on success, non-zero
  * otherwise.
  */
-int ccw_device_tm_start_timeout_key(struct ccw_device *cdev, struct tcw *tcw,
-				    unsigned long intparm, u8 lpm, u8 key,
-				    int expires)
+int ccw_device_tm_start_key(struct ccw_device *cdev, struct tcw *tcw,
+			    unsigned long intparm, u8 lpm, u8 key)
 {
-	int ret;
-
-	ccw_device_set_timeout(cdev, expires);
-	ret = ccw_device_tm_start_key(cdev, tcw, intparm, lpm, key);
-	if (ret != 0)
-		ccw_device_set_timeout(cdev, 0);
-	return ret;
+	return ccw_device_tm_start_timeout_key(cdev, tcw, intparm, lpm, key, 0);
 }
-EXPORT_SYMBOL(ccw_device_tm_start_timeout_key);
+EXPORT_SYMBOL(ccw_device_tm_start_key);
 
 /**
  * ccw_device_tm_start() - perform start function