include/linux/ioprio.h

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