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