text: #ifndef IOPRIO_H
  #define IOPRIO_H
  
  /* Minimal 'sanitized' version of Linux' linux/ioprio.h header file - licence compatible as per information at
   * http://elinux.org/Legal_Issues#Use_of_kernel_header_files_in_user-space  */
  
  #include <sys/syscall.h>
  #include <unistd.h>
  
  /*
   * Gives us 8 prio classes with 13-bits of data for each class
   */
  #define IOPRIO_BITS             (16)
  #define IOPRIO_CLASS_SHIFT      (13)
  #define IOPRIO_PRIO_MASK        ((1UL << IOPRIO_CLASS_SHIFT) - 1)
  
  #define IOPRIO_PRIO_CLASS(mask) ((mask) >> IOPRIO_CLASS_SHIFT)
  #define IOPRIO_PRIO_DATA(mask)  ((mask) & IOPRIO_PRIO_MASK)
  #define IOPRIO_PRIO_VALUE(class, data)  (((class) << IOPRIO_CLASS_SHIFT) | data)
  
  #define ioprio_valid(mask)      (IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
  
  /*
   * These are the io priority groups as implemented by CFQ. RT is the realtime
   * class, it always gets premium service. BE is the best-effort scheduling
   * class, the default for any process. IDLE is the idle scheduling class, it
   * is only served when no one else is using the disk.
   */
  enum {
          IOPRIO_CLASS_NONE,
          IOPRIO_CLASS_RT,
          IOPRIO_CLASS_BE,
          IOPRIO_CLASS_IDLE,
  };
  
  /*
   * 8 best effort priority levels are supported
   */
  #define IOPRIO_BE_NR    (8)
  
  enum {
          IOPRIO_WHO_PROCESS = 1,
          IOPRIO_WHO_PGRP,
          IOPRIO_WHO_USER,
  };
  
  #endif
  