linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 * fs/ioprio.c

 *

 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>

 *

 * 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.txt

 *

 */

#include <linux/gfp.h>

#include <linux/kernel.h>

#include <linux/export.h>

#include <linux/ioprio.h>

#include <linux/cred.h>

#include <linux/blkdev.h>

#include <linux/capability.h>

#include <linux/sched/user.h>

#include <linux/sched/task.h>

#include <linux/syscalls.h>

#include <linux/security.h>

#include <linux/pid_namespace.h>

​

int set_task_ioprio(struct task_struct *task, int ioprio)

{

    int err;

    struct io_context *ioc;

    const struct cred *cred = current_cred(), *tcred;

​

    rcu_read_lock();

    tcred = __task_cred(task);

    if (!uid_eq(tcred->uid, cred->euid) &&

        !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {

        rcu_read_unlock();

        return -EPERM;

    }

    rcu_read_unlock();

​

    err = security_task_setioprio(task, ioprio);

    if (err)

        return err;

​

    ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);

    if (ioc) {

        ioc->ioprio = ioprio;

        put_io_context(ioc);

    }

​

    return err;

}

EXPORT_SYMBOL_GPL(set_task_ioprio);