xref: /openbmc/linux/include/uapi/linux/ioprio.h (revision c7b4b23b)
1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2 #ifndef _UAPI_LINUX_IOPRIO_H
3 #define _UAPI_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  */
28 enum {
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  */
53 enum {
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  */
83 enum {
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  */
ioprio_value(int prioclass,int priolevel,int priohint)110 static __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 /* _UAPI_LINUX_IOPRIO_H */
128