1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef IOPRIO_H
3 #define IOPRIO_H
4 
5 #include <linux/sched.h>
6 #include <linux/sched/rt.h>
7 #include <linux/iocontext.h>
8 
9 /*
10  * Gives us 8 prio classes with 13-bits of data for each class
11  */
12 #define IOPRIO_CLASS_SHIFT	(13)
13 #define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)
14 
15 #define IOPRIO_PRIO_CLASS(mask)	((mask) >> IOPRIO_CLASS_SHIFT)
16 #define IOPRIO_PRIO_DATA(mask)	((mask) & IOPRIO_PRIO_MASK)
17 #define IOPRIO_PRIO_VALUE(class, data)	(((class) << IOPRIO_CLASS_SHIFT) | data)
18 
19 #define ioprio_valid(mask)	(IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
20 
21 /*
22  * These are the io priority groups as implemented by CFQ. RT is the realtime
23  * class, it always gets premium service. BE is the best-effort scheduling
24  * class, the default for any process. IDLE is the idle scheduling class, it
25  * is only served when no one else is using the disk.
26  */
27 enum {
28 	IOPRIO_CLASS_NONE,
29 	IOPRIO_CLASS_RT,
30 	IOPRIO_CLASS_BE,
31 	IOPRIO_CLASS_IDLE,
32 };
33 
34 /*
35  * 8 best effort priority levels are supported
36  */
37 #define IOPRIO_BE_NR	(8)
38 
39 enum {
40 	IOPRIO_WHO_PROCESS = 1,
41 	IOPRIO_WHO_PGRP,
42 	IOPRIO_WHO_USER,
43 };
44 
45 /*
46  * Fallback BE priority
47  */
48 #define IOPRIO_NORM	(4)
49 
50 /*
51  * if process has set io priority explicitly, use that. if not, convert
52  * the cpu scheduler nice value to an io priority
53  */
task_nice_ioprio(struct task_struct * task)54 static inline int task_nice_ioprio(struct task_struct *task)
55 {
56 	return (task_nice(task) + 20) / 5;
57 }
58 
59 /*
60  * This is for the case where the task hasn't asked for a specific IO class.
61  * Check for idle and rt task process, and return appropriate IO class.
62  */
task_nice_ioclass(struct task_struct * task)63 static inline int task_nice_ioclass(struct task_struct *task)
64 {
65 	if (task->policy == SCHED_IDLE)
66 		return IOPRIO_CLASS_IDLE;
67 	else if (task_is_realtime(task))
68 		return IOPRIO_CLASS_RT;
69 	else
70 		return IOPRIO_CLASS_BE;
71 }
72 
73 /*
74  * For inheritance, return the highest of the two given priorities
75  */
76 extern int ioprio_best(unsigned short aprio, unsigned short bprio);
77 
78 extern int set_task_ioprio(struct task_struct *task, int ioprio);
79 
80 #ifdef CONFIG_BLOCK
81 extern int ioprio_check_cap(int ioprio);
82 #else
ioprio_check_cap(int ioprio)83 static inline int ioprio_check_cap(int ioprio)
84 {
85 	return -ENOTBLK;
86 }
87 #endif /* CONFIG_BLOCK */
88 
89 #endif
90