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>
25 #include <linux/capability.h>
26 #include <linux/syscalls.h>
27 #include <linux/security.h>
29 static int set_task_ioprio(struct task_struct *task, int ioprio)
32 struct io_context *ioc;
34 if (task->uid != current->euid &&
35 task->uid != current->uid && !capable(CAP_SYS_NICE))
38 err = security_task_setioprio(task, ioprio);
44 task->ioprio = ioprio;
46 ioc = task->io_context;
47 if (ioc && ioc->set_ioprio)
48 ioc->set_ioprio(ioc, ioprio);
54 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
56 int class = IOPRIO_PRIO_CLASS(ioprio);
57 int data = IOPRIO_PRIO_DATA(ioprio);
58 struct task_struct *p, *g;
59 struct user_struct *user;
64 if (!capable(CAP_SYS_ADMIN))
66 /* fall through, rt has prio field too */
68 if (data >= IOPRIO_BE_NR || data < 0)
72 case IOPRIO_CLASS_IDLE:
73 if (!capable(CAP_SYS_ADMIN))
81 read_lock_irq(&tasklist_lock);
83 case IOPRIO_WHO_PROCESS:
87 p = find_task_by_pid(who);
89 ret = set_task_ioprio(p, ioprio);
93 who = process_group(current);
94 do_each_task_pid(who, PIDTYPE_PGID, p) {
95 ret = set_task_ioprio(p, ioprio);
98 } while_each_task_pid(who, PIDTYPE_PGID, p);
100 case IOPRIO_WHO_USER:
102 user = current->user;
104 user = find_user(who);
109 do_each_thread(g, p) {
112 ret = set_task_ioprio(p, ioprio);
115 } while_each_thread(g, p);
124 read_unlock_irq(&tasklist_lock);
128 asmlinkage long sys_ioprio_get(int which, int who)
130 struct task_struct *g, *p;
131 struct user_struct *user;
134 read_lock_irq(&tasklist_lock);
136 case IOPRIO_WHO_PROCESS:
140 p = find_task_by_pid(who);
144 case IOPRIO_WHO_PGRP:
146 who = process_group(current);
147 do_each_task_pid(who, PIDTYPE_PGID, p) {
151 ret = ioprio_best(ret, p->ioprio);
152 } while_each_task_pid(who, PIDTYPE_PGID, p);
154 case IOPRIO_WHO_USER:
156 user = current->user;
158 user = find_user(who);
163 do_each_thread(g, p) {
164 if (p->uid != user->uid)
169 ret = ioprio_best(ret, p->ioprio);
170 } while_each_thread(g, p);
179 read_unlock_irq(&tasklist_lock);