include/linux/ioprio.h

   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  */
  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  */
  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 #endif