Merge commit 'v3.4.9' into android-t114-3.4
[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/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         int ret;
69
70         switch (class) {
71                 case IOPRIO_CLASS_RT:
72                         if (!capable(CAP_SYS_ADMIN))
73                                 return -EPERM;
74                         /* fall through, rt has prio field too */
75                 case IOPRIO_CLASS_BE:
76                         if (data >= IOPRIO_BE_NR || data < 0)
77                                 return -EINVAL;
78
79                         break;
80                 case IOPRIO_CLASS_IDLE:
81                         break;
82                 case IOPRIO_CLASS_NONE:
83                         if (data)
84                                 return -EINVAL;
85                         break;
86                 default:
87                         return -EINVAL;
88         }
89
90         ret = -ESRCH;
91         rcu_read_lock();
92         switch (which) {
93                 case IOPRIO_WHO_PROCESS:
94                         if (!who)
95                                 p = current;
96                         else
97                                 p = find_task_by_vpid(who);
98                         if (p)
99                                 ret = set_task_ioprio(p, ioprio);
100                         break;
101                 case IOPRIO_WHO_PGRP:
102                         if (!who)
103                                 pgrp = task_pgrp(current);
104                         else
105                                 pgrp = find_vpid(who);
106                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
107                                 ret = set_task_ioprio(p, ioprio);
108                                 if (ret)
109                                         break;
110                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
111                         break;
112                 case IOPRIO_WHO_USER:
113                         if (!who)
114                                 user = current_user();
115                         else
116                                 user = find_user(who);
117
118                         if (!user)
119                                 break;
120
121                         do_each_thread(g, p) {
122                                 if (__task_cred(p)->uid != who)
123                                         continue;
124                                 ret = set_task_ioprio(p, ioprio);
125                                 if (ret)
126                                         goto free_uid;
127                         } while_each_thread(g, p);
128 free_uid:
129                         if (who)
130                                 free_uid(user);
131                         break;
132                 default:
133                         ret = -EINVAL;
134         }
135
136         rcu_read_unlock();
137         return ret;
138 }
139
140 static int get_task_ioprio(struct task_struct *p)
141 {
142         int ret;
143
144         ret = security_task_getioprio(p);
145         if (ret)
146                 goto out;
147         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
148         if (p->io_context)
149                 ret = p->io_context->ioprio;
150 out:
151         return ret;
152 }
153
154 int ioprio_best(unsigned short aprio, unsigned short bprio)
155 {
156         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
157         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
158
159         if (aclass == IOPRIO_CLASS_NONE)
160                 aclass = IOPRIO_CLASS_BE;
161         if (bclass == IOPRIO_CLASS_NONE)
162                 bclass = IOPRIO_CLASS_BE;
163
164         if (aclass == bclass)
165                 return min(aprio, bprio);
166         if (aclass > bclass)
167                 return bprio;
168         else
169                 return aprio;
170 }
171
172 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
173 {
174         struct task_struct *g, *p;
175         struct user_struct *user;
176         struct pid *pgrp;
177         int ret = -ESRCH;
178         int tmpio;
179
180         rcu_read_lock();
181         switch (which) {
182                 case IOPRIO_WHO_PROCESS:
183                         if (!who)
184                                 p = current;
185                         else
186                                 p = find_task_by_vpid(who);
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_thread(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_thread(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 (__task_cred(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         rcu_read_unlock();
234         return ret;
235 }