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Jens Axboe22e2c502005-06-27 10:55:12 +02001/*
2 * fs/ioprio.c
3 *
4 * Copyright (C) 2004 Jens Axboe <axboe@suse.de>
5 *
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;
47 if (ioc && ioc->set_ioprio)
48 ioc->set_ioprio(ioc, ioprio);
49
50 task_unlock(task);
51 return 0;
52}
53
Anton Blanchardcf366802005-07-07 17:56:13 -070054asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
Jens Axboe22e2c502005-06-27 10:55:12 +020055{
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;
60 int ret;
61
62 switch (class) {
63 case IOPRIO_CLASS_RT:
64 if (!capable(CAP_SYS_ADMIN))
65 return -EPERM;
66 /* fall through, rt has prio field too */
67 case IOPRIO_CLASS_BE:
68 if (data >= IOPRIO_BE_NR || data < 0)
69 return -EINVAL;
70
71 break;
72 case IOPRIO_CLASS_IDLE:
Linus Torvaldsf6fdd7d2005-08-20 18:51:29 -070073 if (!capable(CAP_SYS_ADMIN))
74 return -EPERM;
Jens Axboe22e2c502005-06-27 10:55:12 +020075 break;
76 default:
77 return -EINVAL;
78 }
79
80 ret = -ESRCH;
81 read_lock_irq(&tasklist_lock);
82 switch (which) {
83 case IOPRIO_WHO_PROCESS:
84 if (!who)
85 p = current;
86 else
87 p = find_task_by_pid(who);
88 if (p)
89 ret = set_task_ioprio(p, ioprio);
90 break;
91 case IOPRIO_WHO_PGRP:
92 if (!who)
93 who = process_group(current);
94 do_each_task_pid(who, PIDTYPE_PGID, p) {
95 ret = set_task_ioprio(p, ioprio);
96 if (ret)
97 break;
98 } while_each_task_pid(who, PIDTYPE_PGID, p);
99 break;
100 case IOPRIO_WHO_USER:
101 if (!who)
102 user = current->user;
103 else
104 user = find_user(who);
105
106 if (!user)
107 break;
108
109 do_each_thread(g, p) {
110 if (p->uid != who)
111 continue;
112 ret = set_task_ioprio(p, ioprio);
113 if (ret)
114 break;
115 } while_each_thread(g, p);
116
117 if (who)
118 free_uid(user);
119 break;
120 default:
121 ret = -EINVAL;
122 }
123
124 read_unlock_irq(&tasklist_lock);
125 return ret;
126}
127
Anton Blanchardcf366802005-07-07 17:56:13 -0700128asmlinkage long sys_ioprio_get(int which, int who)
Jens Axboe22e2c502005-06-27 10:55:12 +0200129{
130 struct task_struct *g, *p;
131 struct user_struct *user;
132 int ret = -ESRCH;
133
134 read_lock_irq(&tasklist_lock);
135 switch (which) {
136 case IOPRIO_WHO_PROCESS:
137 if (!who)
138 p = current;
139 else
140 p = find_task_by_pid(who);
141 if (p)
142 ret = p->ioprio;
143 break;
144 case IOPRIO_WHO_PGRP:
145 if (!who)
146 who = process_group(current);
147 do_each_task_pid(who, PIDTYPE_PGID, p) {
148 if (ret == -ESRCH)
149 ret = p->ioprio;
150 else
151 ret = ioprio_best(ret, p->ioprio);
152 } while_each_task_pid(who, PIDTYPE_PGID, p);
153 break;
154 case IOPRIO_WHO_USER:
155 if (!who)
156 user = current->user;
157 else
158 user = find_user(who);
159
160 if (!user)
161 break;
162
163 do_each_thread(g, p) {
164 if (p->uid != user->uid)
165 continue;
166 if (ret == -ESRCH)
167 ret = p->ioprio;
168 else
169 ret = ioprio_best(ret, p->ioprio);
170 } while_each_thread(g, p);
171
172 if (who)
173 free_uid(user);
174 break;
175 default:
176 ret = -EINVAL;
177 }
178
179 read_unlock_irq(&tasklist_lock);
180 return ret;
181}
182