4 * Copyright (C) 2004 Jens Axboe <axboe@suse.de>
6 * Helper functions for setting/querying io priorities of processes. The
7 * system calls closely mimmick getpriority/setpriority, see the man page for
8 * those. The prio argument is a composite of prio class and prio data, where
9 * the data argument has meaning within that class. The standard scheduling
10 * classes have 8 distinct prio levels, with 0 being the highest prio and 7
13 * IOW, setting BE scheduling class with prio 2 is done ala:
15 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
17 * ioprio_set(PRIO_PROCESS, pid, prio);
19 * See also Documentation/block/ioprio.txt
22 #include <linux/kernel.h>
23 #include <linux/ioprio.h>
24 #include <linux/blkdev.h>
26 static int set_task_ioprio(struct task_struct *task, int ioprio)
28 struct io_context *ioc;
30 if (task->uid != current->euid &&
31 task->uid != current->uid && !capable(CAP_SYS_NICE))
36 task->ioprio = ioprio;
38 ioc = task->io_context;
39 if (ioc && ioc->set_ioprio)
40 ioc->set_ioprio(ioc, ioprio);
46 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
48 int class = IOPRIO_PRIO_CLASS(ioprio);
49 int data = IOPRIO_PRIO_DATA(ioprio);
50 struct task_struct *p, *g;
51 struct user_struct *user;
56 if (!capable(CAP_SYS_ADMIN))
58 /* fall through, rt has prio field too */
60 if (data >= IOPRIO_BE_NR || data < 0)
64 case IOPRIO_CLASS_IDLE:
71 read_lock_irq(&tasklist_lock);
73 case IOPRIO_WHO_PROCESS:
77 p = find_task_by_pid(who);
79 ret = set_task_ioprio(p, ioprio);
83 who = process_group(current);
84 do_each_task_pid(who, PIDTYPE_PGID, p) {
85 ret = set_task_ioprio(p, ioprio);
88 } while_each_task_pid(who, PIDTYPE_PGID, p);
94 user = find_user(who);
99 do_each_thread(g, p) {
102 ret = set_task_ioprio(p, ioprio);
105 } while_each_thread(g, p);
114 read_unlock_irq(&tasklist_lock);
118 asmlinkage long sys_ioprio_get(int which, int who)
120 struct task_struct *g, *p;
121 struct user_struct *user;
124 read_lock_irq(&tasklist_lock);
126 case IOPRIO_WHO_PROCESS:
130 p = find_task_by_pid(who);
134 case IOPRIO_WHO_PGRP:
136 who = process_group(current);
137 do_each_task_pid(who, PIDTYPE_PGID, p) {
141 ret = ioprio_best(ret, p->ioprio);
142 } while_each_task_pid(who, PIDTYPE_PGID, p);
144 case IOPRIO_WHO_USER:
146 user = current->user;
148 user = find_user(who);
153 do_each_thread(g, p) {
154 if (p->uid != user->uid)
159 ret = ioprio_best(ret, p->ioprio);
160 } while_each_thread(g, p);
169 read_unlock_irq(&tasklist_lock);