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Linux kernel mirror (for testing)
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kernel
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linux
1/*
2 * fs/ioprio.c
3 *
4 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
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>
25#include <linux/capability.h>
26#include <linux/syscalls.h>
27#include <linux/security.h>
28#include <linux/pid_namespace.h>
29
30static int set_task_ioprio(struct task_struct *task, int ioprio)
31{
32 int err;
33 struct io_context *ioc;
34
35 if (task->uid != current->euid &&
36 task->uid != current->uid && !capable(CAP_SYS_NICE))
37 return -EPERM;
38
39 err = security_task_setioprio(task, ioprio);
40 if (err)
41 return err;
42
43 task_lock(task);
44
45 task->ioprio = ioprio;
46
47 ioc = task->io_context;
48 /* see wmb() in current_io_context() */
49 smp_read_barrier_depends();
50
51 if (ioc)
52 ioc->ioprio_changed = 1;
53
54 task_unlock(task);
55 return 0;
56}
57
58asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
59{
60 int class = IOPRIO_PRIO_CLASS(ioprio);
61 int data = IOPRIO_PRIO_DATA(ioprio);
62 struct task_struct *p, *g;
63 struct user_struct *user;
64 struct pid *pgrp;
65 int ret;
66
67 switch (class) {
68 case IOPRIO_CLASS_RT:
69 if (!capable(CAP_SYS_ADMIN))
70 return -EPERM;
71 /* fall through, rt has prio field too */
72 case IOPRIO_CLASS_BE:
73 if (data >= IOPRIO_BE_NR || data < 0)
74 return -EINVAL;
75
76 break;
77 case IOPRIO_CLASS_IDLE:
78 if (!capable(CAP_SYS_ADMIN))
79 return -EPERM;
80 break;
81 case IOPRIO_CLASS_NONE:
82 if (data)
83 return -EINVAL;
84 break;
85 default:
86 return -EINVAL;
87 }
88
89 ret = -ESRCH;
90 /*
91 * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
92 * so we can't use rcu_read_lock(). See re-copy of ->ioprio
93 * in copy_process().
94 */
95 read_lock(&tasklist_lock);
96 switch (which) {
97 case IOPRIO_WHO_PROCESS:
98 if (!who)
99 p = current;
100 else
101 p = find_task_by_vpid(who);
102 if (p)
103 ret = set_task_ioprio(p, ioprio);
104 break;
105 case IOPRIO_WHO_PGRP:
106 if (!who)
107 pgrp = task_pgrp(current);
108 else
109 pgrp = find_vpid(who);
110 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
111 ret = set_task_ioprio(p, ioprio);
112 if (ret)
113 break;
114 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
115 break;
116 case IOPRIO_WHO_USER:
117 if (!who)
118 user = current->user;
119 else
120 user = find_user(who);
121
122 if (!user)
123 break;
124
125 do_each_thread(g, p) {
126 if (p->uid != who)
127 continue;
128 ret = set_task_ioprio(p, ioprio);
129 if (ret)
130 goto free_uid;
131 } while_each_thread(g, p);
132free_uid:
133 if (who)
134 free_uid(user);
135 break;
136 default:
137 ret = -EINVAL;
138 }
139
140 read_unlock(&tasklist_lock);
141 return ret;
142}
143
144static int get_task_ioprio(struct task_struct *p)
145{
146 int ret;
147
148 ret = security_task_getioprio(p);
149 if (ret)
150 goto out;
151 ret = p->ioprio;
152out:
153 return ret;
154}
155
156int ioprio_best(unsigned short aprio, unsigned short bprio)
157{
158 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
159 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
160
161 if (aclass == IOPRIO_CLASS_NONE)
162 aclass = IOPRIO_CLASS_BE;
163 if (bclass == IOPRIO_CLASS_NONE)
164 bclass = IOPRIO_CLASS_BE;
165
166 if (aclass == bclass)
167 return min(aprio, bprio);
168 if (aclass > bclass)
169 return bprio;
170 else
171 return aprio;
172}
173
174asmlinkage long sys_ioprio_get(int which, int who)
175{
176 struct task_struct *g, *p;
177 struct user_struct *user;
178 struct pid *pgrp;
179 int ret = -ESRCH;
180 int tmpio;
181
182 read_lock(&tasklist_lock);
183 switch (which) {
184 case IOPRIO_WHO_PROCESS:
185 if (!who)
186 p = current;
187 else
188 p = find_task_by_vpid(who);
189 if (p)
190 ret = get_task_ioprio(p);
191 break;
192 case IOPRIO_WHO_PGRP:
193 if (!who)
194 pgrp = task_pgrp(current);
195 else
196 pgrp = find_vpid(who);
197 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
198 tmpio = get_task_ioprio(p);
199 if (tmpio < 0)
200 continue;
201 if (ret == -ESRCH)
202 ret = tmpio;
203 else
204 ret = ioprio_best(ret, tmpio);
205 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
206 break;
207 case IOPRIO_WHO_USER:
208 if (!who)
209 user = current->user;
210 else
211 user = find_user(who);
212
213 if (!user)
214 break;
215
216 do_each_thread(g, p) {
217 if (p->uid != user->uid)
218 continue;
219 tmpio = get_task_ioprio(p);
220 if (tmpio < 0)
221 continue;
222 if (ret == -ESRCH)
223 ret = tmpio;
224 else
225 ret = ioprio_best(ret, tmpio);
226 } while_each_thread(g, p);
227
228 if (who)
229 free_uid(user);
230 break;
231 default:
232 ret = -EINVAL;
233 }
234
235 read_unlock(&tasklist_lock);
236 return ret;
237}
238