block: change ioprio_valid() to an inline function

Change the ioprio_valid() macro in include/usapi/linux/ioprio.h to an
inline function declared on the kernel side in include/linux/ioprio.h.
Also improve checks on the class value by checking the upper bound
value.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Link: https://lore.kernel.org/r/20210811033702.368488-4-damien.lemoal@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/ioprio.h

@@ -8,6 +8,16 @@
 
 #include <uapi/linux/ioprio.h>
 
+/*
+ * Check that a priority value has a valid class.
+ */
+static inline bool ioprio_valid(unsigned short ioprio)
+{
+	unsigned short class = IOPRIO_PRIO_CLASS(ioprio);
+
+	return class > IOPRIO_CLASS_NONE && class <= IOPRIO_CLASS_IDLE;
+}
+
 /*
  * if process has set io priority explicitly, use that. if not, convert
  * the cpu scheduler nice value to an io priority

include/uapi/linux/ioprio.h

@@ -27,8 +27,6 @@ enum {
 	IOPRIO_CLASS_IDLE,
 };
 
-#define ioprio_valid(mask)	(IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
-
 /*
  * 8 best effort priority levels are supported
  */