pid namespaces: changes to show virtual ids to user
[linux-2.6.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/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
30 static 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
58 asmlinkage 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                 default:
82                         return -EINVAL;
83         }
84
85         ret = -ESRCH;
86         /*
87          * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
88          * so we can't use rcu_read_lock(). See re-copy of ->ioprio
89          * in copy_process().
90          */
91         read_lock(&tasklist_lock);
92         switch (which) {
93                 case IOPRIO_WHO_PROCESS:
94                         if (!who)
95                                 p = current;
96                         else
97                                 p = find_task_by_pid_ns(who,
98                                                 current->nsproxy->pid_ns);
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_task(pgrp, PIDTYPE_PGID, p) {
108                                 ret = set_task_ioprio(p, ioprio);
109                                 if (ret)
110                                         break;
111                         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
112                         break;
113                 case IOPRIO_WHO_USER:
114                         if (!who)
115                                 user = current->user;
116                         else
117                                 user = find_user(who);
118
119                         if (!user)
120                                 break;
121
122                         do_each_thread(g, p) {
123                                 if (p->uid != who)
124                                         continue;
125                                 ret = set_task_ioprio(p, ioprio);
126                                 if (ret)
127                                         goto free_uid;
128                         } while_each_thread(g, p);
129 free_uid:
130                         if (who)
131                                 free_uid(user);
132                         break;
133                 default:
134                         ret = -EINVAL;
135         }
136
137         read_unlock(&tasklist_lock);
138         return ret;
139 }
140
141 static int get_task_ioprio(struct task_struct *p)
142 {
143         int ret;
144
145         ret = security_task_getioprio(p);
146         if (ret)
147                 goto out;
148         ret = p->ioprio;
149 out:
150         return ret;
151 }
152
153 int ioprio_best(unsigned short aprio, unsigned short bprio)
154 {
155         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
156         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
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
171 asmlinkage long sys_ioprio_get(int which, int who)
172 {
173         struct task_struct *g, *p;
174         struct user_struct *user;
175         struct pid *pgrp;
176         int ret = -ESRCH;
177         int tmpio;
178
179         read_lock(&tasklist_lock);
180         switch (which) {
181                 case IOPRIO_WHO_PROCESS:
182                         if (!who)
183                                 p = current;
184                         else
185                                 p = find_task_by_pid_ns(who,
186                                                 current->nsproxy->pid_ns);
187                         if (p)
188                                 ret = get_task_ioprio(p);
189                         break;
190                 case IOPRIO_WHO_PGRP:
191                         if (!who)
192                                 pgrp = task_pgrp(current);
193                         else
194                                 pgrp = find_vpid(who);
195                         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
196                                 tmpio = get_task_ioprio(p);
197                                 if (tmpio < 0)
198                                         continue;
199                                 if (ret == -ESRCH)
200                                         ret = tmpio;
201                                 else
202                                         ret = ioprio_best(ret, tmpio);
203                         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
204                         break;
205                 case IOPRIO_WHO_USER:
206                         if (!who)
207                                 user = current->user;
208                         else
209                                 user = find_user(who);
210
211                         if (!user)
212                                 break;
213
214                         do_each_thread(g, p) {
215                                 if (p->uid != user->uid)
216                                         continue;
217                                 tmpio = get_task_ioprio(p);
218                                 if (tmpio < 0)
219                                         continue;
220                                 if (ret == -ESRCH)
221                                         ret = tmpio;
222                                 else
223                                         ret = ioprio_best(ret, tmpio);
224                         } while_each_thread(g, p);
225
226                         if (who)
227                                 free_uid(user);
228                         break;
229                 default:
230                         ret = -EINVAL;
231         }
232
233         read_unlock(&tasklist_lock);
234         return ret;
235 }
236