linux/include/linux/ioprio.h
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   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
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