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/gfp.h>
23 #include <linux/kernel.h>
24 #include <linux/ioprio.h>
25 #include <linux/blkdev.h>
26 #include <linux/capability.h>
27 #include <linux/syscalls.h>
28 #include <linux/security.h>
29 #include <linux/pid_namespace.h>
30
set_task_ioprio(struct task_struct * task,int ioprio)31 int set_task_ioprio(struct task_struct *task, int ioprio)
32 {
33 int err;
34 struct io_context *ioc;
35 const struct cred *cred = current_cred(), *tcred;
36
37 rcu_read_lock();
38 tcred = __task_cred(task);
39 if (tcred->uid != cred->euid &&
40 tcred->uid != cred->uid && !capable(CAP_SYS_NICE)) {
41 rcu_read_unlock();
42 return -EPERM;
43 }
44 rcu_read_unlock();
45
46 err = security_task_setioprio(task, ioprio);
47 if (err)
48 return err;
49
50 task_lock(task);
51 do {
52 ioc = task->io_context;
53 /* see wmb() in current_io_context() */
54 smp_read_barrier_depends();
55 if (ioc)
56 break;
57
58 ioc = alloc_io_context(GFP_ATOMIC, -1);
59 if (!ioc) {
60 err = -ENOMEM;
61 break;
62 }
63 task->io_context = ioc;
64 } while (1);
65
66 if (!err) {
67 ioc->ioprio = ioprio;
68 ioc->ioprio_changed = 1;
69 }
70
71 task_unlock(task);
72 return err;
73 }
74 EXPORT_SYMBOL_GPL(set_task_ioprio);
75
SYSCALL_DEFINE3(ioprio_set,int,which,int,who,int,ioprio)76 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
77 {
78 int class = IOPRIO_PRIO_CLASS(ioprio);
79 int data = IOPRIO_PRIO_DATA(ioprio);
80 struct task_struct *p, *g;
81 struct user_struct *user;
82 struct pid *pgrp;
83 int ret;
84
85 switch (class) {
86 case IOPRIO_CLASS_RT:
87 if (!capable(CAP_SYS_ADMIN))
88 return -EPERM;
89 /* fall through, rt has prio field too */
90 case IOPRIO_CLASS_BE:
91 if (data >= IOPRIO_BE_NR || data < 0)
92 return -EINVAL;
93
94 break;
95 case IOPRIO_CLASS_IDLE:
96 break;
97 case IOPRIO_CLASS_NONE:
98 if (data)
99 return -EINVAL;
100 break;
101 default:
102 return -EINVAL;
103 }
104
105 ret = -ESRCH;
106 rcu_read_lock();
107 switch (which) {
108 case IOPRIO_WHO_PROCESS:
109 if (!who)
110 p = current;
111 else
112 p = find_task_by_vpid(who);
113 if (p)
114 ret = set_task_ioprio(p, ioprio);
115 break;
116 case IOPRIO_WHO_PGRP:
117 if (!who)
118 pgrp = task_pgrp(current);
119 else
120 pgrp = find_vpid(who);
121 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
122 ret = set_task_ioprio(p, ioprio);
123 if (ret)
124 break;
125 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
126 break;
127 case IOPRIO_WHO_USER:
128 if (!who)
129 user = current_user();
130 else
131 user = find_user(who);
132
133 if (!user)
134 break;
135
136 do_each_thread(g, p) {
137 if (__task_cred(p)->uid != who)
138 continue;
139 ret = set_task_ioprio(p, ioprio);
140 if (ret)
141 goto free_uid;
142 } while_each_thread(g, p);
143 free_uid:
144 if (who)
145 free_uid(user);
146 break;
147 default:
148 ret = -EINVAL;
149 }
150
151 rcu_read_unlock();
152 return ret;
153 }
154
get_task_ioprio(struct task_struct * p)155 static int get_task_ioprio(struct task_struct *p)
156 {
157 int ret;
158
159 ret = security_task_getioprio(p);
160 if (ret)
161 goto out;
162 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
163 if (p->io_context)
164 ret = p->io_context->ioprio;
165 out:
166 return ret;
167 }
168
ioprio_best(unsigned short aprio,unsigned short bprio)169 int ioprio_best(unsigned short aprio, unsigned short bprio)
170 {
171 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
172 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
173
174 if (aclass == IOPRIO_CLASS_NONE)
175 aclass = IOPRIO_CLASS_BE;
176 if (bclass == IOPRIO_CLASS_NONE)
177 bclass = IOPRIO_CLASS_BE;
178
179 if (aclass == bclass)
180 return min(aprio, bprio);
181 if (aclass > bclass)
182 return bprio;
183 else
184 return aprio;
185 }
186
SYSCALL_DEFINE2(ioprio_get,int,which,int,who)187 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
188 {
189 struct task_struct *g, *p;
190 struct user_struct *user;
191 struct pid *pgrp;
192 int ret = -ESRCH;
193 int tmpio;
194
195 rcu_read_lock();
196 switch (which) {
197 case IOPRIO_WHO_PROCESS:
198 if (!who)
199 p = current;
200 else
201 p = find_task_by_vpid(who);
202 if (p)
203 ret = get_task_ioprio(p);
204 break;
205 case IOPRIO_WHO_PGRP:
206 if (!who)
207 pgrp = task_pgrp(current);
208 else
209 pgrp = find_vpid(who);
210 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
211 tmpio = get_task_ioprio(p);
212 if (tmpio < 0)
213 continue;
214 if (ret == -ESRCH)
215 ret = tmpio;
216 else
217 ret = ioprio_best(ret, tmpio);
218 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
219 break;
220 case IOPRIO_WHO_USER:
221 if (!who)
222 user = current_user();
223 else
224 user = find_user(who);
225
226 if (!user)
227 break;
228
229 do_each_thread(g, p) {
230 if (__task_cred(p)->uid != user->uid)
231 continue;
232 tmpio = get_task_ioprio(p);
233 if (tmpio < 0)
234 continue;
235 if (ret == -ESRCH)
236 ret = tmpio;
237 else
238 ret = ioprio_best(ret, tmpio);
239 } while_each_thread(g, p);
240
241 if (who)
242 free_uid(user);
243 break;
244 default:
245 ret = -EINVAL;
246 }
247
248 rcu_read_unlock();
249 return ret;
250 }
251