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Jens Axboe22e2c502005-06-27 10:55:12 +02001/*
2 * fs/ioprio.c
3 *
Jens Axboe0fe23472006-09-04 15:41:16 +02004 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
Jens Axboe22e2c502005-06-27 10:55:12 +02005 *
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
11 * being the lowest.
12 *
13 * IOW, setting BE scheduling class with prio 2 is done ala:
14 *
15 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
16 *
17 * ioprio_set(PRIO_PROCESS, pid, prio);
18 *
19 * See also Documentation/block/ioprio.txt
20 *
21 */
22#include <linux/kernel.h>
23#include <linux/ioprio.h>
24#include <linux/blkdev.h>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080025#include <linux/capability.h>
Adrian Bunk9abdc4c2005-11-08 16:57:02 +010026#include <linux/syscalls.h>
James Morris03e68062006-06-23 02:03:58 -070027#include <linux/security.h>
Jens Axboe22e2c502005-06-27 10:55:12 +020028
29static int set_task_ioprio(struct task_struct *task, int ioprio)
30{
James Morris03e68062006-06-23 02:03:58 -070031 int err;
Jens Axboe22e2c502005-06-27 10:55:12 +020032 struct io_context *ioc;
33
34 if (task->uid != current->euid &&
35 task->uid != current->uid && !capable(CAP_SYS_NICE))
36 return -EPERM;
37
James Morris03e68062006-06-23 02:03:58 -070038 err = security_task_setioprio(task, ioprio);
39 if (err)
40 return err;
41
Jens Axboe22e2c502005-06-27 10:55:12 +020042 task_lock(task);
43
44 task->ioprio = ioprio;
45
46 ioc = task->io_context;
Oleg Nesterov9f83e452006-08-21 08:34:15 +020047 /* see wmb() in current_io_context() */
48 smp_read_barrier_depends();
49
Jens Axboefc463792006-08-29 09:05:44 +020050 if (ioc)
51 ioc->ioprio_changed = 1;
Jens Axboe22e2c502005-06-27 10:55:12 +020052
53 task_unlock(task);
54 return 0;
55}
56
Anton Blanchardcf366802005-07-07 17:56:13 -070057asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
Jens Axboe22e2c502005-06-27 10:55:12 +020058{
59 int class = IOPRIO_PRIO_CLASS(ioprio);
60 int data = IOPRIO_PRIO_DATA(ioprio);
61 struct task_struct *p, *g;
62 struct user_struct *user;
63 int ret;
64
65 switch (class) {
66 case IOPRIO_CLASS_RT:
67 if (!capable(CAP_SYS_ADMIN))
68 return -EPERM;
69 /* fall through, rt has prio field too */
70 case IOPRIO_CLASS_BE:
71 if (data >= IOPRIO_BE_NR || data < 0)
72 return -EINVAL;
73
74 break;
75 case IOPRIO_CLASS_IDLE:
Linus Torvaldsf6fdd7d2005-08-20 18:51:29 -070076 if (!capable(CAP_SYS_ADMIN))
77 return -EPERM;
Jens Axboe22e2c502005-06-27 10:55:12 +020078 break;
79 default:
80 return -EINVAL;
81 }
82
83 ret = -ESRCH;
Oleg Nesterovcf342e52006-08-29 09:17:41 +020084 /*
85 * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
86 * so we can't use rcu_read_lock(). See re-copy of ->ioprio
87 * in copy_process().
88 */
89 read_lock(&tasklist_lock);
Jens Axboe22e2c502005-06-27 10:55:12 +020090 switch (which) {
91 case IOPRIO_WHO_PROCESS:
92 if (!who)
93 p = current;
94 else
95 p = find_task_by_pid(who);
96 if (p)
97 ret = set_task_ioprio(p, ioprio);
98 break;
99 case IOPRIO_WHO_PGRP:
100 if (!who)
101 who = process_group(current);
102 do_each_task_pid(who, PIDTYPE_PGID, p) {
103 ret = set_task_ioprio(p, ioprio);
104 if (ret)
105 break;
106 } while_each_task_pid(who, PIDTYPE_PGID, p);
107 break;
108 case IOPRIO_WHO_USER:
109 if (!who)
110 user = current->user;
111 else
112 user = find_user(who);
113
114 if (!user)
115 break;
116
117 do_each_thread(g, p) {
118 if (p->uid != who)
119 continue;
120 ret = set_task_ioprio(p, ioprio);
121 if (ret)
Oleg Nesterov78bd4d42006-08-21 08:33:23 +0200122 goto free_uid;
Jens Axboe22e2c502005-06-27 10:55:12 +0200123 } while_each_thread(g, p);
Oleg Nesterov78bd4d42006-08-21 08:33:23 +0200124free_uid:
Jens Axboe22e2c502005-06-27 10:55:12 +0200125 if (who)
126 free_uid(user);
127 break;
128 default:
129 ret = -EINVAL;
130 }
131
Oleg Nesterovcf342e52006-08-29 09:17:41 +0200132 read_unlock(&tasklist_lock);
Jens Axboe22e2c502005-06-27 10:55:12 +0200133 return ret;
134}
135
David Quigleya1836a42006-06-30 01:55:49 -0700136static int get_task_ioprio(struct task_struct *p)
137{
138 int ret;
139
140 ret = security_task_getioprio(p);
141 if (ret)
142 goto out;
143 ret = p->ioprio;
144out:
145 return ret;
146}
147
Oleg Nesterove014ff82006-08-21 10:02:50 +0200148int ioprio_best(unsigned short aprio, unsigned short bprio)
149{
150 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
151 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
152
153 if (!ioprio_valid(aprio))
154 return bprio;
155 if (!ioprio_valid(bprio))
156 return aprio;
157
158 if (aclass == IOPRIO_CLASS_NONE)
159 aclass = IOPRIO_CLASS_BE;
160 if (bclass == IOPRIO_CLASS_NONE)
161 bclass = IOPRIO_CLASS_BE;
162
163 if (aclass == bclass)
164 return min(aprio, bprio);
165 if (aclass > bclass)
166 return bprio;
167 else
168 return aprio;
169}
170
Anton Blanchardcf366802005-07-07 17:56:13 -0700171asmlinkage long sys_ioprio_get(int which, int who)
Jens Axboe22e2c502005-06-27 10:55:12 +0200172{
173 struct task_struct *g, *p;
174 struct user_struct *user;
175 int ret = -ESRCH;
David Quigleya1836a42006-06-30 01:55:49 -0700176 int tmpio;
Jens Axboe22e2c502005-06-27 10:55:12 +0200177
Oleg Nesterovcf342e52006-08-29 09:17:41 +0200178 read_lock(&tasklist_lock);
Jens Axboe22e2c502005-06-27 10:55:12 +0200179 switch (which) {
180 case IOPRIO_WHO_PROCESS:
181 if (!who)
182 p = current;
183 else
184 p = find_task_by_pid(who);
185 if (p)
David Quigleya1836a42006-06-30 01:55:49 -0700186 ret = get_task_ioprio(p);
Jens Axboe22e2c502005-06-27 10:55:12 +0200187 break;
188 case IOPRIO_WHO_PGRP:
189 if (!who)
190 who = process_group(current);
191 do_each_task_pid(who, PIDTYPE_PGID, p) {
David Quigleya1836a42006-06-30 01:55:49 -0700192 tmpio = get_task_ioprio(p);
193 if (tmpio < 0)
194 continue;
Jens Axboe22e2c502005-06-27 10:55:12 +0200195 if (ret == -ESRCH)
David Quigleya1836a42006-06-30 01:55:49 -0700196 ret = tmpio;
Jens Axboe22e2c502005-06-27 10:55:12 +0200197 else
David Quigleya1836a42006-06-30 01:55:49 -0700198 ret = ioprio_best(ret, tmpio);
Jens Axboe22e2c502005-06-27 10:55:12 +0200199 } while_each_task_pid(who, PIDTYPE_PGID, p);
200 break;
201 case IOPRIO_WHO_USER:
202 if (!who)
203 user = current->user;
204 else
205 user = find_user(who);
206
207 if (!user)
208 break;
209
210 do_each_thread(g, p) {
211 if (p->uid != user->uid)
212 continue;
David Quigleya1836a42006-06-30 01:55:49 -0700213 tmpio = get_task_ioprio(p);
214 if (tmpio < 0)
215 continue;
Jens Axboe22e2c502005-06-27 10:55:12 +0200216 if (ret == -ESRCH)
David Quigleya1836a42006-06-30 01:55:49 -0700217 ret = tmpio;
Jens Axboe22e2c502005-06-27 10:55:12 +0200218 else
David Quigleya1836a42006-06-30 01:55:49 -0700219 ret = ioprio_best(ret, tmpio);
Jens Axboe22e2c502005-06-27 10:55:12 +0200220 } while_each_thread(g, p);
221
222 if (who)
223 free_uid(user);
224 break;
225 default:
226 ret = -EINVAL;
227 }
228
Oleg Nesterovcf342e52006-08-29 09:17:41 +0200229 read_unlock(&tasklist_lock);
Jens Axboe22e2c502005-06-27 10:55:12 +0200230 return ret;
231}
232