linux/block/ioprio.c

// SPDX-License-Identifier: GPL-2.0
/*
 * fs/ioprio.c
 *
 * Copyright (C) 2004 Jens Axboe <[email protected]>
 *
 * Helper functions for setting/querying io priorities of processes. The
 * system calls closely mimmick getpriority/setpriority, see the man page for
 * those. The prio argument is a composite of prio class and prio data, where
 * the data argument has meaning within that class. The standard scheduling
 * classes have 8 distinct prio levels, with 0 being the highest prio and 7
 * being the lowest.
 *
 * IOW, setting BE scheduling class with prio 2 is done ala:
 *
 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
 *
 * ioprio_set(PRIO_PROCESS, pid, prio);
 *
 * See also Documentation/block/ioprio.rst
 *
 */
#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/ioprio.h>
#include <linux/cred.h>
#include <linux/blkdev.h>
#include <linux/capability.h>
#include <linux/syscalls.h>
#include <linux/security.h>
#include <linux/pid_namespace.h>

int ioprio_check_cap(int ioprio)
{ … }

SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
{ … }

static int get_task_ioprio(struct task_struct *p)
{ … }

/*
 * Return raw IO priority value as set by userspace. We use this for
 * ioprio_get(pid, IOPRIO_WHO_PROCESS) so that we keep historical behavior and
 * also so that userspace can distinguish unset IO priority (which just gets
 * overriden based on task's nice value) from IO priority set to some value.
 */
static int get_task_raw_ioprio(struct task_struct *p)
{ … }

static int ioprio_best(unsigned short aprio, unsigned short bprio)
{ … }

SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
{ … }