cifs: don't instantiate new dentries in readdir for inodes that need to be revalidate...
[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 (!uid_eq(tcred->uid, cred->euid) &&
41             !uid_eq(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 = 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                                 if (!uid_eq(task_uid(p), uid))
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         rcu_read_unlock();
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 = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
152         if (p->io_context)
153                 ret = p->io_context->ioprio;
154 out:
155         return ret;
156 }
157
158 int ioprio_best(unsigned short aprio, unsigned short bprio)
159 {
160         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
161         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
162
163         if (aclass == IOPRIO_CLASS_NONE)
164                 aclass = IOPRIO_CLASS_BE;
165         if (bclass == IOPRIO_CLASS_NONE)
166                 bclass = IOPRIO_CLASS_BE;
167
168         if (aclass == bclass)
169                 return min(aprio, bprio);
170         if (aclass > bclass)
171                 return bprio;
172         else
173                 return aprio;
174 }
175
176 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
177 {
178         struct task_struct *g, *p;
179         struct user_struct *user;
180         struct pid *pgrp;
181         kuid_t uid;
182         int ret = -ESRCH;
183         int tmpio;
184
185         rcu_read_lock();
186         switch (which) {
187                 case IOPRIO_WHO_PROCESS:
188                         if (!who)
189                                 p = current;
190                         else
191                                 p = find_task_by_vpid(who);
192                         if (p)
193                                 ret = get_task_ioprio(p);
194                         break;
195                 case IOPRIO_WHO_PGRP:
196                         if (!who)
197                                 pgrp = task_pgrp(current);
198                         else
199                                 pgrp = find_vpid(who);
200                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
201                                 tmpio = get_task_ioprio(p);
202                                 if (tmpio < 0)
203                                         continue;
204                                 if (ret == -ESRCH)
205                                         ret = tmpio;
206                                 else
207                                         ret = ioprio_best(ret, tmpio);
208                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
209                         break;
210                 case IOPRIO_WHO_USER:
211                         uid = make_kuid(current_user_ns(), who);
212                         if (!who)
213                                 user = current_user();
214                         else
215                                 user = find_user(uid);
216
217                         if (!user)
218                                 break;
219
220                         do_each_thread(g, p) {
221                                 if (!uid_eq(task_uid(p), user->uid))
222                                         continue;
223                                 tmpio = get_task_ioprio(p);
224                                 if (tmpio < 0)
225                                         continue;
226                                 if (ret == -ESRCH)
227                                         ret = tmpio;
228                                 else
229                                         ret = ioprio_best(ret, tmpio);
230                         } while_each_thread(g, p);
231
232                         if (who)
233                                 free_uid(user);
234                         break;
235                 default:
236                         ret = -EINVAL;
237         }
238
239         rcu_read_unlock();
240         return ret;
241 }