include/linux/ioprio.h

   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  */
  26 enum {
  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
  38 enum {
  39         IOPRIO_WHO_PROCESS = 1,
  40         IOPRIO_WHO_PGRP,
  41         IOPRIO_WHO_USER,
  42 };
  43
  44 /*
  45  * if process has set io priority explicitly, use that. if not, convert
  46  * the cpu scheduler nice value to an io priority
  47  */
  48 #define IOPRIO_NORM     (4)
  49 static inline int task_ioprio(struct io_context *ioc)
  50 {
  51         if (ioprio_valid(ioc->ioprio))
  52                 return IOPRIO_PRIO_DATA(ioc->ioprio);
  53
  54         return IOPRIO_NORM;
  55 }
  56
  57 static inline int task_ioprio_class(struct io_context *ioc)
  58 {
  59         if (ioprio_valid(ioc->ioprio))
  60                 return IOPRIO_PRIO_CLASS(ioc->ioprio);
  61
  62         return IOPRIO_CLASS_BE;
  63 }
  64
  65 static inline int task_nice_ioprio(struct task_struct *task)
  66 {
  67         return (task_nice(task) + 20) / 5;
  68 }
  69
  70 /*
  71  * This is for the case where the task hasn't asked for a specific IO class.
  72  * Check for idle and rt task process, and return appropriate IO class.
  73  */
  74 static inline int task_nice_ioclass(struct task_struct *task)
  75 {
  76         if (task->policy == SCHED_IDLE)
  77                 return IOPRIO_CLASS_IDLE;
  78         else if (task->policy == SCHED_FIFO || task->policy == SCHED_RR)
  79                 return IOPRIO_CLASS_RT;
  80         else
  81                 return IOPRIO_CLASS_BE;
  82 }
  83
  84 /*
  85  * For inheritance, return the highest of the two given priorities
  86  */
  87 extern int ioprio_best(unsigned short aprio, unsigned short bprio);
  88
  89 #endif