1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
  2#ifndef _LINUX_IOPRIO_H
  3#define _LINUX_IOPRIO_H
  4
  5#include <linux/stddef.h>
  6#include <linux/types.h>
  7
  8/*
  9 * Gives us 8 prio classes with 13-bits of data for each class
 10 */
 11#define IOPRIO_CLASS_SHIFT	13
 12#define IOPRIO_NR_CLASSES	8
 13#define IOPRIO_CLASS_MASK	(IOPRIO_NR_CLASSES - 1)
 14#define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)
 15
 16#define IOPRIO_PRIO_CLASS(ioprio)	\
 17	(((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
 18#define IOPRIO_PRIO_DATA(ioprio)	((ioprio) & IOPRIO_PRIO_MASK)
 19
 20/*
 21 * These are the io priority classes as implemented by the BFQ and mq-deadline
 22 * schedulers. RT is the realtime class, it always gets premium service. For
 23 * ATA disks supporting NCQ IO priority, RT class IOs will be processed using
 24 * high priority NCQ commands. BE is the best-effort scheduling class, the
 25 * default for any process. IDLE is the idle scheduling class, it is only
 26 * served when no one else is using the disk.
 27 */
 28enum {
 29	IOPRIO_CLASS_NONE	= 0,
 30	IOPRIO_CLASS_RT		= 1,
 31	IOPRIO_CLASS_BE		= 2,
 32	IOPRIO_CLASS_IDLE	= 3,
 33
 34	/* Special class to indicate an invalid ioprio value */
 35	IOPRIO_CLASS_INVALID	= 7,
 36};
 37
 38/*
 39 * The RT and BE priority classes both support up to 8 priority levels that
 40 * can be specified using the lower 3-bits of the priority data.
 41 */
 42#define IOPRIO_LEVEL_NR_BITS		3
 43#define IOPRIO_NR_LEVELS		(1 << IOPRIO_LEVEL_NR_BITS)
 44#define IOPRIO_LEVEL_MASK		(IOPRIO_NR_LEVELS - 1)
 45#define IOPRIO_PRIO_LEVEL(ioprio)	((ioprio) & IOPRIO_LEVEL_MASK)
 46
 47#define IOPRIO_BE_NR			IOPRIO_NR_LEVELS
 48
 49/*
 50 * Possible values for the "which" argument of the ioprio_get() and
 51 * ioprio_set() system calls (see "man ioprio_set").
 52 */
 53enum {
 54	IOPRIO_WHO_PROCESS = 1,
 55	IOPRIO_WHO_PGRP,
 56	IOPRIO_WHO_USER,
 57};
 58
 59/*
 60 * Fallback BE class priority level.
 61 */
 62#define IOPRIO_NORM	4
 63#define IOPRIO_BE_NORM	IOPRIO_NORM
 64
 65/*
 66 * The 10 bits between the priority class and the priority level are used to
 67 * optionally define I/O hints for any combination of I/O priority class and
 68 * level. Depending on the kernel configuration, I/O scheduler being used and
 69 * the target I/O device being used, hints can influence how I/Os are processed
 70 * without affecting the I/O scheduling ordering defined by the I/O priority
 71 * class and level.
 72 */
 73#define IOPRIO_HINT_SHIFT		IOPRIO_LEVEL_NR_BITS
 74#define IOPRIO_HINT_NR_BITS		10
 75#define IOPRIO_NR_HINTS			(1 << IOPRIO_HINT_NR_BITS)
 76#define IOPRIO_HINT_MASK		(IOPRIO_NR_HINTS - 1)
 77#define IOPRIO_PRIO_HINT(ioprio)	\
 78	(((ioprio) >> IOPRIO_HINT_SHIFT) & IOPRIO_HINT_MASK)
 79
 80/*
 81 * I/O hints.
 82 */
 83enum {
 84	/* No hint */
 85	IOPRIO_HINT_NONE = 0,
 86
 87	/*
 88	 * Device command duration limits: indicate to the device a desired
 89	 * duration limit for the commands that will be used to process an I/O.
 90	 * These will currently only be effective for SCSI and ATA devices that
 91	 * support the command duration limits feature. If this feature is
 92	 * enabled, then the commands issued to the device to process an I/O with
 93	 * one of these hints set will have the duration limit index (dld field)
 94	 * set to the value of the hint.
 95	 */
 96	IOPRIO_HINT_DEV_DURATION_LIMIT_1 = 1,
 97	IOPRIO_HINT_DEV_DURATION_LIMIT_2 = 2,
 98	IOPRIO_HINT_DEV_DURATION_LIMIT_3 = 3,
 99	IOPRIO_HINT_DEV_DURATION_LIMIT_4 = 4,
100	IOPRIO_HINT_DEV_DURATION_LIMIT_5 = 5,
101	IOPRIO_HINT_DEV_DURATION_LIMIT_6 = 6,
102	IOPRIO_HINT_DEV_DURATION_LIMIT_7 = 7,
103};
104
105#define IOPRIO_BAD_VALUE(val, max) ((val) < 0 || (val) >= (max))
106
107/*
108 * Return an I/O priority value based on a class, a level and a hint.
109 */
110static __always_inline __u16 ioprio_value(int prioclass, int priolevel,
111					  int priohint)
112{
113	if (IOPRIO_BAD_VALUE(prioclass, IOPRIO_NR_CLASSES) ||
114	    IOPRIO_BAD_VALUE(priolevel, IOPRIO_NR_LEVELS) ||
115	    IOPRIO_BAD_VALUE(priohint, IOPRIO_NR_HINTS))
116		return IOPRIO_CLASS_INVALID << IOPRIO_CLASS_SHIFT;
117
118	return (prioclass << IOPRIO_CLASS_SHIFT) |
119		(priohint << IOPRIO_HINT_SHIFT) | priolevel;
120}
121
122#define IOPRIO_PRIO_VALUE(prioclass, priolevel)			\
123	ioprio_value(prioclass, priolevel, IOPRIO_HINT_NONE)
124#define IOPRIO_PRIO_VALUE_HINT(prioclass, priolevel, priohint)	\
125	ioprio_value(prioclass, priolevel, priohint)
126
127#endif /* _LINUX_IOPRIO_H */