173 lines
3.5 KiB
C
173 lines
3.5 KiB
C
/*
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* fs/ioprio.c
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*
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* Copyright (C) 2004 Jens Axboe <axboe@suse.de>
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*
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* Helper functions for setting/querying io priorities of processes. The
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* system calls closely mimmick getpriority/setpriority, see the man page for
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* those. The prio argument is a composite of prio class and prio data, where
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* the data argument has meaning within that class. The standard scheduling
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* classes have 8 distinct prio levels, with 0 being the highest prio and 7
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* being the lowest.
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*
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* IOW, setting BE scheduling class with prio 2 is done ala:
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*
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* unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
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*
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* ioprio_set(PRIO_PROCESS, pid, prio);
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*
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* See also Documentation/block/ioprio.txt
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*
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*/
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#include <linux/kernel.h>
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#include <linux/ioprio.h>
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#include <linux/blkdev.h>
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static int set_task_ioprio(struct task_struct *task, int ioprio)
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{
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struct io_context *ioc;
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if (task->uid != current->euid &&
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task->uid != current->uid && !capable(CAP_SYS_NICE))
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return -EPERM;
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task_lock(task);
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task->ioprio = ioprio;
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ioc = task->io_context;
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if (ioc && ioc->set_ioprio)
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ioc->set_ioprio(ioc, ioprio);
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task_unlock(task);
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return 0;
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}
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asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
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{
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int class = IOPRIO_PRIO_CLASS(ioprio);
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int data = IOPRIO_PRIO_DATA(ioprio);
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struct task_struct *p, *g;
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struct user_struct *user;
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int ret;
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switch (class) {
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case IOPRIO_CLASS_RT:
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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/* fall through, rt has prio field too */
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case IOPRIO_CLASS_BE:
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if (data >= IOPRIO_BE_NR || data < 0)
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return -EINVAL;
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break;
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case IOPRIO_CLASS_IDLE:
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break;
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default:
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return -EINVAL;
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}
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ret = -ESRCH;
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read_lock_irq(&tasklist_lock);
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switch (which) {
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case IOPRIO_WHO_PROCESS:
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if (!who)
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p = current;
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else
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p = find_task_by_pid(who);
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if (p)
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ret = set_task_ioprio(p, ioprio);
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break;
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case IOPRIO_WHO_PGRP:
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if (!who)
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who = process_group(current);
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do_each_task_pid(who, PIDTYPE_PGID, p) {
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ret = set_task_ioprio(p, ioprio);
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if (ret)
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break;
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} while_each_task_pid(who, PIDTYPE_PGID, p);
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break;
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case IOPRIO_WHO_USER:
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if (!who)
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user = current->user;
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else
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user = find_user(who);
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if (!user)
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break;
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do_each_thread(g, p) {
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if (p->uid != who)
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continue;
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ret = set_task_ioprio(p, ioprio);
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if (ret)
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break;
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} while_each_thread(g, p);
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if (who)
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free_uid(user);
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break;
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default:
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ret = -EINVAL;
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}
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read_unlock_irq(&tasklist_lock);
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return ret;
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}
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asmlinkage long sys_ioprio_get(int which, int who)
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{
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struct task_struct *g, *p;
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struct user_struct *user;
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int ret = -ESRCH;
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read_lock_irq(&tasklist_lock);
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switch (which) {
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case IOPRIO_WHO_PROCESS:
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if (!who)
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p = current;
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else
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p = find_task_by_pid(who);
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if (p)
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ret = p->ioprio;
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break;
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case IOPRIO_WHO_PGRP:
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if (!who)
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who = process_group(current);
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do_each_task_pid(who, PIDTYPE_PGID, p) {
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if (ret == -ESRCH)
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ret = p->ioprio;
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else
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ret = ioprio_best(ret, p->ioprio);
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} while_each_task_pid(who, PIDTYPE_PGID, p);
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break;
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case IOPRIO_WHO_USER:
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if (!who)
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user = current->user;
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else
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user = find_user(who);
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if (!user)
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break;
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do_each_thread(g, p) {
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if (p->uid != user->uid)
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continue;
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if (ret == -ESRCH)
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ret = p->ioprio;
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else
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ret = ioprio_best(ret, p->ioprio);
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} while_each_thread(g, p);
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if (who)
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free_uid(user);
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break;
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default:
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ret = -EINVAL;
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}
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read_unlock_irq(&tasklist_lock);
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return ret;
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}
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