do not integrate with kread
[linux-2.6.git] / fs / ioprio.c
1 /*
2  * fs/ioprio.c
3  *
4  * Copyright (C) 2004 Jens Axboe <axboe@suse.de>
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/vs_base.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 && ioc->set_ioprio)
52                 ioc->set_ioprio(ioc, ioprio);
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         int ret;
65
66         switch (class) {
67                 case IOPRIO_CLASS_RT:
68                         if (!capable(CAP_SYS_ADMIN))
69                                 return -EPERM;
70                         /* fall through, rt has prio field too */
71                 case IOPRIO_CLASS_BE:
72                         if (data >= IOPRIO_BE_NR || data < 0)
73                                 return -EINVAL;
74
75                         break;
76                 case IOPRIO_CLASS_IDLE:
77                         if (!capable(CAP_SYS_ADMIN))
78                                 return -EPERM;
79                         break;
80                 default:
81                         return -EINVAL;
82         }
83
84         ret = -ESRCH;
85         read_lock_irq(&tasklist_lock);
86         switch (which) {
87                 case IOPRIO_WHO_PROCESS:
88                         if (!who)
89                                 p = current;
90                         else
91                                 p = find_task_by_pid(who);
92                         if (p)
93                                 ret = set_task_ioprio(p, ioprio);
94                         break;
95                 case IOPRIO_WHO_PGRP:
96                         if (!who)
97                                 who = process_group(current);
98                         do_each_task_pid(who, PIDTYPE_PGID, p) {
99                                 ret = set_task_ioprio(p, ioprio);
100                                 if (ret)
101                                         break;
102                         } while_each_task_pid(who, PIDTYPE_PGID, p);
103                         break;
104                 case IOPRIO_WHO_USER:
105                         if (!who)
106                                 user = current->user;
107                         else
108                                 user = find_user(vx_current_xid(), who);
109
110                         if (!user)
111                                 break;
112
113                         do_each_thread(g, p) {
114                                 if (p->uid != who)
115                                         continue;
116                                 ret = set_task_ioprio(p, ioprio);
117                                 if (ret)
118                                         goto free_uid;
119                         } while_each_thread(g, p);
120 free_uid:
121                         if (who)
122                                 free_uid(user);
123                         break;
124                 default:
125                         ret = -EINVAL;
126         }
127
128         read_unlock_irq(&tasklist_lock);
129         return ret;
130 }
131
132 static int get_task_ioprio(struct task_struct *p)
133 {
134         int ret;
135
136         ret = security_task_getioprio(p);
137         if (ret)
138                 goto out;
139         ret = p->ioprio;
140 out:
141         return ret;
142 }
143
144 int ioprio_best(unsigned short aprio, unsigned short bprio)
145 {
146         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
147         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
148
149         if (!ioprio_valid(aprio))
150                 return bprio;
151         if (!ioprio_valid(bprio))
152                 return aprio;
153
154         if (aclass == IOPRIO_CLASS_NONE)
155                 aclass = IOPRIO_CLASS_BE;
156         if (bclass == IOPRIO_CLASS_NONE)
157                 bclass = IOPRIO_CLASS_BE;
158
159         if (aclass == bclass)
160                 return min(aprio, bprio);
161         if (aclass > bclass)
162                 return bprio;
163         else
164                 return aprio;
165 }
166
167 asmlinkage long sys_ioprio_get(int which, int who)
168 {
169         struct task_struct *g, *p;
170         struct user_struct *user;
171         int ret = -ESRCH;
172         int tmpio;
173
174         read_lock_irq(&tasklist_lock);
175         switch (which) {
176                 case IOPRIO_WHO_PROCESS:
177                         if (!who)
178                                 p = current;
179                         else
180                                 p = find_task_by_pid(who);
181                         if (p)
182                                 ret = get_task_ioprio(p);
183                         break;
184                 case IOPRIO_WHO_PGRP:
185                         if (!who)
186                                 who = process_group(current);
187                         do_each_task_pid(who, PIDTYPE_PGID, p) {
188                                 tmpio = get_task_ioprio(p);
189                                 if (tmpio < 0)
190                                         continue;
191                                 if (ret == -ESRCH)
192                                         ret = tmpio;
193                                 else
194                                         ret = ioprio_best(ret, tmpio);
195                         } while_each_task_pid(who, PIDTYPE_PGID, p);
196                         break;
197                 case IOPRIO_WHO_USER:
198                         if (!who)
199                                 user = current->user;
200                         else
201                                 user = find_user(vx_current_xid(), who);
202
203                         if (!user)
204                                 break;
205
206                         do_each_thread(g, p) {
207                                 if (p->uid != user->uid)
208                                         continue;
209                                 tmpio = get_task_ioprio(p);
210                                 if (tmpio < 0)
211                                         continue;
212                                 if (ret == -ESRCH)
213                                         ret = tmpio;
214                                 else
215                                         ret = ioprio_best(ret, tmpio);
216                         } while_each_thread(g, p);
217
218                         if (who)
219                                 free_uid(user);
220                         break;
221                 default:
222                         ret = -EINVAL;
223         }
224
225         read_unlock_irq(&tasklist_lock);
226         return ret;
227 }
228