1#ifndef IOPRIO_H
2#define IOPRIO_H
3
4#include <linux/sched.h>
5#include <linux/iocontext.h>
6
7/*
8 * Gives us 8 prio classes with 13-bits of data for each class
9 */
10#define IOPRIO_BITS		(16)
11#define IOPRIO_CLASS_SHIFT	(13)
12#define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)
13
14#define IOPRIO_PRIO_CLASS(mask)	((mask) >> IOPRIO_CLASS_SHIFT)
15#define IOPRIO_PRIO_DATA(mask)	((mask) & IOPRIO_PRIO_MASK)
16#define IOPRIO_PRIO_VALUE(class, data)	(((class) << IOPRIO_CLASS_SHIFT) | data)
17
18#define ioprio_valid(mask)	(IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
19
20/*
21 * These are the io priority groups as implemented by CFQ. RT is the realtime
22 * class, it always gets premium service. BE is the best-effort scheduling
23 * class, the default for any process. IDLE is the idle scheduling class, it
24 * is only served when no one else is using the disk.
25 */
26enum {
27	IOPRIO_CLASS_NONE,
28	IOPRIO_CLASS_RT,
29	IOPRIO_CLASS_BE,
30	IOPRIO_CLASS_IDLE,
31};
32
33/*
34 * 8 best effort priority levels are supported
35 */
36#define IOPRIO_BE_NR	(8)
37
38enum {
39	IOPRIO_WHO_PROCESS = 1,
40	IOPRIO_WHO_PGRP,
41	IOPRIO_WHO_USER,
42};
43
44/*
45 * Fallback BE priority
46 */
47#define IOPRIO_NORM	(4)
48
49/*
50 * if process has set io priority explicitly, use that. if not, convert
51 * the cpu scheduler nice value to an io priority
52 */
53static inline int task_nice_ioprio(struct task_struct *task)
54{
55	return (task_nice(task) + 20) / 5;
56}
57
58/*
59 * This is for the case where the task hasn't asked for a specific IO class.
60 * Check for idle and rt task process, and return appropriate IO class.
61 */
62static inline int task_nice_ioclass(struct task_struct *task)
63{
64	if (task->policy == SCHED_IDLE)
65		return IOPRIO_CLASS_IDLE;
66	else if (task->policy == SCHED_FIFO || task->policy == SCHED_RR)
67		return IOPRIO_CLASS_RT;
68	else
69		return IOPRIO_CLASS_BE;
70}
71
72/*
73 * For inheritance, return the highest of the two given priorities
74 */
75extern int ioprio_best(unsigned short aprio, unsigned short bprio);
76
77extern int set_task_ioprio(struct task_struct *task, int ioprio);
78
79#endif
80