genirq/proc: Return proper error code when irq_set_affinity() fails

write_irq_affinity() returns the number of written bytes, which means
success, unconditionally whether the actual irq_set_affinity() call
succeeded or not.

Add proper error handling and pass the error code returned from
irq_set_affinity() back to user space in case of failure.

[ tglx: Fixed coding style and massaged changelog ]

Signed-off-by: Wen Yang <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Jiang Biao <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

Author: taskset

kernel/irq/proc.c

@@ -154,8 +154,9 @@ static ssize_t write_irq_affinity(int type, struct file *file,
 		 */
 		err = irq_select_affinity_usr(irq) ? -EINVAL : count;
 	} else {
-		irq_set_affinity(irq, new_value);
-		err = count;
+		err = irq_set_affinity(irq, new_value);
+		if (!err)
+			err = count;
 	}
 
 free_cpumask: