userns: Disassociate user_struct from the user_namespace.
[linux-3.10.git] / fs / ioprio.c
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/export.h>
25 #include <linux/ioprio.h>
26 #include <linux/blkdev.h>
27 #include <linux/capability.h>
28 #include <linux/syscalls.h>
29 #include <linux/security.h>
30 #include <linux/pid_namespace.h>
31
32 int set_task_ioprio(struct task_struct *task, int ioprio)
33 {
34         int err;
35         struct io_context *ioc;
36         const struct cred *cred = current_cred(), *tcred;
37
38         rcu_read_lock();
39         tcred = __task_cred(task);
40         if (tcred->uid != cred->euid &&
41             tcred->uid != cred->uid && !capable(CAP_SYS_NICE)) {
42                 rcu_read_unlock();
43                 return -EPERM;
44         }
45         rcu_read_unlock();
46
47         err = security_task_setioprio(task, ioprio);
48         if (err)
49                 return err;
50
51         ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
52         if (ioc) {
53                 ioc_ioprio_changed(ioc, ioprio);
54                 put_io_context(ioc);
55         }
56
57         return err;
58 }
59 EXPORT_SYMBOL_GPL(set_task_ioprio);
60
61 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
62 {
63         int class = IOPRIO_PRIO_CLASS(ioprio);
64         int data = IOPRIO_PRIO_DATA(ioprio);
65         struct task_struct *p, *g;
66         struct user_struct *user;
67         struct pid *pgrp;
68         kuid_t uid;
69         int ret;
70
71         switch (class) {
72                 case IOPRIO_CLASS_RT:
73                         if (!capable(CAP_SYS_ADMIN))
74                                 return -EPERM;
75                         /* fall through, rt has prio field too */
76                 case IOPRIO_CLASS_BE:
77                         if (data >= IOPRIO_BE_NR || data < 0)
78                                 return -EINVAL;
79
80                         break;
81                 case IOPRIO_CLASS_IDLE:
82                         break;
83                 case IOPRIO_CLASS_NONE:
84                         if (data)
85                                 return -EINVAL;
86                         break;
87                 default:
88                         return -EINVAL;
89         }
90
91         ret = -ESRCH;
92         rcu_read_lock();
93         switch (which) {
94                 case IOPRIO_WHO_PROCESS:
95                         if (!who)
96                                 p = current;
97                         else
98                                 p = find_task_by_vpid(who);
99                         if (p)
100                                 ret = set_task_ioprio(p, ioprio);
101                         break;
102                 case IOPRIO_WHO_PGRP:
103                         if (!who)
104                                 pgrp = task_pgrp(current);
105                         else
106                                 pgrp = find_vpid(who);
107                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
108                                 ret = set_task_ioprio(p, ioprio);
109                                 if (ret)
110                                         break;
111                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
112                         break;
113                 case IOPRIO_WHO_USER:
114                         uid = make_kuid(current_user_ns(), who);
115                         if (!uid_valid(uid))
116                                 break;
117                         if (!who)
118                                 user = current_user();
119                         else
120                                 user = find_user(uid);
121
122                         if (!user)
123                                 break;
124
125                         do_each_thread(g, p) {
126                                 const struct cred *tcred = __task_cred(p);
127                                 kuid_t tcred_uid = make_kuid(tcred->user_ns, tcred->uid);
128                                 if (!uid_eq(tcred_uid, uid))
129                                         continue;
130                                 ret = set_task_ioprio(p, ioprio);
131                                 if (ret)
132                                         goto free_uid;
133                         } while_each_thread(g, p);
134 free_uid:
135                         if (who)
136                                 free_uid(user);
137                         break;
138                 default:
139                         ret = -EINVAL;
140         }
141
142         rcu_read_unlock();
143         return ret;
144 }
145
146 static int get_task_ioprio(struct task_struct *p)
147 {
148         int ret;
149
150         ret = security_task_getioprio(p);
151         if (ret)
152                 goto out;
153         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
154         if (p->io_context)
155                 ret = p->io_context->ioprio;
156 out:
157         return ret;
158 }
159
160 int ioprio_best(unsigned short aprio, unsigned short bprio)
161 {
162         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
163         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
164
165         if (aclass == IOPRIO_CLASS_NONE)
166                 aclass = IOPRIO_CLASS_BE;
167         if (bclass == IOPRIO_CLASS_NONE)
168                 bclass = IOPRIO_CLASS_BE;
169
170         if (aclass == bclass)
171                 return min(aprio, bprio);
172         if (aclass > bclass)
173                 return bprio;
174         else
175                 return aprio;
176 }
177
178 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
179 {
180         struct task_struct *g, *p;
181         struct user_struct *user;
182         struct pid *pgrp;
183         kuid_t uid;
184         int ret = -ESRCH;
185         int tmpio;
186
187         rcu_read_lock();
188         switch (which) {
189                 case IOPRIO_WHO_PROCESS:
190                         if (!who)
191                                 p = current;
192                         else
193                                 p = find_task_by_vpid(who);
194                         if (p)
195                                 ret = get_task_ioprio(p);
196                         break;
197                 case IOPRIO_WHO_PGRP:
198                         if (!who)
199                                 pgrp = task_pgrp(current);
200                         else
201                                 pgrp = find_vpid(who);
202                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
203                                 tmpio = get_task_ioprio(p);
204                                 if (tmpio < 0)
205                                         continue;
206                                 if (ret == -ESRCH)
207                                         ret = tmpio;
208                                 else
209                                         ret = ioprio_best(ret, tmpio);
210                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
211                         break;
212                 case IOPRIO_WHO_USER:
213                         uid = make_kuid(current_user_ns(), who);
214                         if (!who)
215                                 user = current_user();
216                         else
217                                 user = find_user(uid);
218
219                         if (!user)
220                                 break;
221
222                         do_each_thread(g, p) {
223                                 const struct cred *tcred = __task_cred(p);
224                                 kuid_t tcred_uid = make_kuid(tcred->user_ns, tcred->uid);
225                                 if (!uid_eq(tcred_uid, user->uid))
226                                         continue;
227                                 tmpio = get_task_ioprio(p);
228                                 if (tmpio < 0)
229                                         continue;
230                                 if (ret == -ESRCH)
231                                         ret = tmpio;
232                                 else
233                                         ret = ioprio_best(ret, tmpio);
234                         } while_each_thread(g, p);
235
236                         if (who)
237                                 free_uid(user);
238                         break;
239                 default:
240                         ret = -EINVAL;
241         }
242
243         rcu_read_unlock();
244         return ret;
245 }