include/uapi/linux/ioprio.h

Source file repositories/reference/linux-study-clean/include/uapi/linux/ioprio.h

File Facts

System
Linux kernel
Corpus path
include/uapi/linux/ioprio.h
Extension
.h
Size
4190 bytes
Lines
128
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

#ifndef _UAPI_LINUX_IOPRIO_H
#define _UAPI_LINUX_IOPRIO_H

#include <linux/stddef.h>
#include <linux/types.h>

/*
 * Gives us 8 prio classes with 13-bits of data for each class
 */
#define IOPRIO_CLASS_SHIFT	13
#define IOPRIO_NR_CLASSES	8
#define IOPRIO_CLASS_MASK	(IOPRIO_NR_CLASSES - 1)
#define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)

#define IOPRIO_PRIO_CLASS(ioprio)	\
	(((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
#define IOPRIO_PRIO_DATA(ioprio)	((ioprio) & IOPRIO_PRIO_MASK)

/*
 * These are the io priority classes as implemented by the BFQ and mq-deadline
 * schedulers. RT is the realtime class, it always gets premium service. For
 * ATA disks supporting NCQ IO priority, RT class IOs will be processed using
 * high priority NCQ commands. 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	= 0,
	IOPRIO_CLASS_RT		= 1,
	IOPRIO_CLASS_BE		= 2,
	IOPRIO_CLASS_IDLE	= 3,

	/* Special class to indicate an invalid ioprio value */
	IOPRIO_CLASS_INVALID	= 7,
};

/*
 * The RT and BE priority classes both support up to 8 priority levels that
 * can be specified using the lower 3-bits of the priority data.
 */
#define IOPRIO_LEVEL_NR_BITS		3
#define IOPRIO_NR_LEVELS		(1 << IOPRIO_LEVEL_NR_BITS)
#define IOPRIO_LEVEL_MASK		(IOPRIO_NR_LEVELS - 1)
#define IOPRIO_PRIO_LEVEL(ioprio)	((ioprio) & IOPRIO_LEVEL_MASK)

#define IOPRIO_BE_NR			IOPRIO_NR_LEVELS

/*
 * Possible values for the "which" argument of the ioprio_get() and
 * ioprio_set() system calls (see "man ioprio_set").
 */
enum {
	IOPRIO_WHO_PROCESS = 1,
	IOPRIO_WHO_PGRP,
	IOPRIO_WHO_USER,
};

/*
 * Fallback BE class priority level.
 */
#define IOPRIO_NORM	4
#define IOPRIO_BE_NORM	IOPRIO_NORM

/*
 * The 10 bits between the priority class and the priority level are used to
 * optionally define I/O hints for any combination of I/O priority class and
 * level. Depending on the kernel configuration, I/O scheduler being used and
 * the target I/O device being used, hints can influence how I/Os are processed
 * without affecting the I/O scheduling ordering defined by the I/O priority
 * class and level.
 */
#define IOPRIO_HINT_SHIFT		IOPRIO_LEVEL_NR_BITS
#define IOPRIO_HINT_NR_BITS		10
#define IOPRIO_NR_HINTS			(1 << IOPRIO_HINT_NR_BITS)
#define IOPRIO_HINT_MASK		(IOPRIO_NR_HINTS - 1)
#define IOPRIO_PRIO_HINT(ioprio)	\
	(((ioprio) >> IOPRIO_HINT_SHIFT) & IOPRIO_HINT_MASK)

/*
 * I/O hints.
 */
enum {
	/* No hint */
	IOPRIO_HINT_NONE = 0,

	/*
	 * Device command duration limits: indicate to the device a desired
	 * duration limit for the commands that will be used to process an I/O.
	 * These will currently only be effective for SCSI and ATA devices that
	 * support the command duration limits feature. If this feature is

Annotation

Implementation Notes