1 files changed, 63 insertions, 5 deletions

diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
index f70f2596a6bf..4c4806e8230b 100644
--- a/include/uapi/linux/ioprio.h
+++ b/include/uapi/linux/ioprio.h
@@ -17,7 +17,7 @@
 	 ((data) & IOPRIO_PRIO_MASK))
 
 /*
- * These are the io priority groups as implemented by the BFQ and mq-deadline
+ * These are the io priority classes as implemented by the BFQ and mq-deadline
  * schedulers. RT is the realtime class, it always gets premium service. For
  * ATA disks supporting NCQ IO priority, RT class IOs will be processed using
  * high priority NCQ commands. BE is the best-effort scheduling class, the
@@ -32,11 +32,20 @@ enum {
 };
 
 /*
- * The RT and BE priority classes both support up to 8 priority levels.
+ * The RT and BE priority classes both support up to 8 priority levels that
+ * can be specified using the lower 3-bits of the priority data.
  */
-#define IOPRIO_NR_LEVELS	8
-#define IOPRIO_BE_NR		IOPRIO_NR_LEVELS
+#define IOPRIO_LEVEL_NR_BITS		3
+#define IOPRIO_NR_LEVELS		(1 << IOPRIO_LEVEL_NR_BITS)
+#define IOPRIO_LEVEL_MASK		(IOPRIO_NR_LEVELS - 1)
+#define IOPRIO_PRIO_LEVEL(ioprio)	((ioprio) & IOPRIO_LEVEL_MASK)
 
+#define IOPRIO_BE_NR			IOPRIO_NR_LEVELS
+
+/*
+ * Possible values for the "which" argument of the ioprio_get() and
+ * ioprio_set() system calls (see "man ioprio_set").
+ */
 enum {
 	IOPRIO_WHO_PROCESS = 1,
 	IOPRIO_WHO_PGRP,
@@ -44,9 +53,58 @@ enum {
 };
 
 /*
- * Fallback BE priority level.
+ * Fallback BE class priority level.
  */
 #define IOPRIO_NORM	4
 #define IOPRIO_BE_NORM	IOPRIO_NORM
 
+/*
+ * The 10 bits between the priority class and the priority level are used to
+ * optionally define I/O hints for any combination of I/O priority class and
+ * level. Depending on the kernel configuration, I/O scheduler being used and
+ * the target I/O device being used, hints can influence how I/Os are processed
+ * without affecting the I/O scheduling ordering defined by the I/O priority
+ * class and level.
+ */
+#define IOPRIO_HINT_SHIFT		IOPRIO_LEVEL_NR_BITS
+#define IOPRIO_HINT_NR_BITS		10
+#define IOPRIO_NR_HINTS			(1 << IOPRIO_HINT_NR_BITS)
+#define IOPRIO_HINT_MASK		(IOPRIO_NR_HINTS - 1)
+#define IOPRIO_PRIO_HINT(ioprio)	\
+	(((ioprio) >> IOPRIO_HINT_SHIFT) & IOPRIO_HINT_MASK)
+
+/*
+ * Alternate macro for IOPRIO_PRIO_VALUE() to define an I/O priority with
+ * a class, level and hint.
+ */
+#define IOPRIO_PRIO_VALUE_HINT(class, level, hint)		 \
+	((((class) & IOPRIO_CLASS_MASK) << IOPRIO_CLASS_SHIFT) | \
+	 (((hint) & IOPRIO_HINT_MASK) << IOPRIO_HINT_SHIFT) |	 \
+	 ((level) & IOPRIO_LEVEL_MASK))
+
+/*
+ * I/O hints.
+ */
+enum {
+	/* No hint */
+	IOPRIO_HINT_NONE = 0,
+
+	/*
+	 * Device command duration limits: indicate to the device a desired
+	 * duration limit for the commands that will be used to process an I/O.
+	 * These will currently only be effective for SCSI and ATA devices that
+	 * support the command duration limits feature. If this feature is
+	 * enabled, then the commands issued to the device to process an I/O with
+	 * one of these hints set will have the duration limit index (dld field)
+	 * set to the value of the hint.
+	 */
+	IOPRIO_HINT_DEV_DURATION_LIMIT_1 = 1,
+	IOPRIO_HINT_DEV_DURATION_LIMIT_2 = 2,
+	IOPRIO_HINT_DEV_DURATION_LIMIT_3 = 3,
+	IOPRIO_HINT_DEV_DURATION_LIMIT_4 = 4,
+	IOPRIO_HINT_DEV_DURATION_LIMIT_5 = 5,
+	IOPRIO_HINT_DEV_DURATION_LIMIT_6 = 6,
+	IOPRIO_HINT_DEV_DURATION_LIMIT_7 = 7,
+};
+
 #endif /* _UAPI_LINUX_IOPRIO_H */