Merge git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched
[linux-2.6] / 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                 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);
132 free_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
144 static 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;
152 out:
153         return ret;
154 }
155
156 int 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
174 asmlinkage 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