xfs: validate acl count
[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/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
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
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
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
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
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 }