Fix nasty ncpfs symlink handling bug.
[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
26 static int set_task_ioprio(struct task_struct *task, int ioprio)
27 {
28         struct io_context *ioc;
29
30         if (task->uid != current->euid &&
31             task->uid != current->uid && !capable(CAP_SYS_NICE))
32                 return -EPERM;
33
34         task_lock(task);
35
36         task->ioprio = ioprio;
37
38         ioc = task->io_context;
39         if (ioc && ioc->set_ioprio)
40                 ioc->set_ioprio(ioc, ioprio);
41
42         task_unlock(task);
43         return 0;
44 }
45
46 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
47 {
48         int class = IOPRIO_PRIO_CLASS(ioprio);
49         int data = IOPRIO_PRIO_DATA(ioprio);
50         struct task_struct *p, *g;
51         struct user_struct *user;
52         int ret;
53
54         switch (class) {
55                 case IOPRIO_CLASS_RT:
56                         if (!capable(CAP_SYS_ADMIN))
57                                 return -EPERM;
58                         /* fall through, rt has prio field too */
59                 case IOPRIO_CLASS_BE:
60                         if (data >= IOPRIO_BE_NR || data < 0)
61                                 return -EINVAL;
62
63                         break;
64                 case IOPRIO_CLASS_IDLE:
65                         break;
66                 default:
67                         return -EINVAL;
68         }
69
70         ret = -ESRCH;
71         read_lock_irq(&tasklist_lock);
72         switch (which) {
73                 case IOPRIO_WHO_PROCESS:
74                         if (!who)
75                                 p = current;
76                         else
77                                 p = find_task_by_pid(who);
78                         if (p)
79                                 ret = set_task_ioprio(p, ioprio);
80                         break;
81                 case IOPRIO_WHO_PGRP:
82                         if (!who)
83                                 who = process_group(current);
84                         do_each_task_pid(who, PIDTYPE_PGID, p) {
85                                 ret = set_task_ioprio(p, ioprio);
86                                 if (ret)
87                                         break;
88                         } while_each_task_pid(who, PIDTYPE_PGID, p);
89                         break;
90                 case IOPRIO_WHO_USER:
91                         if (!who)
92                                 user = current->user;
93                         else
94                                 user = find_user(who);
95
96                         if (!user)
97                                 break;
98
99                         do_each_thread(g, p) {
100                                 if (p->uid != who)
101                                         continue;
102                                 ret = set_task_ioprio(p, ioprio);
103                                 if (ret)
104                                         break;
105                         } while_each_thread(g, p);
106
107                         if (who)
108                                 free_uid(user);
109                         break;
110                 default:
111                         ret = -EINVAL;
112         }
113
114         read_unlock_irq(&tasklist_lock);
115         return ret;
116 }
117
118 asmlinkage long sys_ioprio_get(int which, int who)
119 {
120         struct task_struct *g, *p;
121         struct user_struct *user;
122         int ret = -ESRCH;
123
124         read_lock_irq(&tasklist_lock);
125         switch (which) {
126                 case IOPRIO_WHO_PROCESS:
127                         if (!who)
128                                 p = current;
129                         else
130                                 p = find_task_by_pid(who);
131                         if (p)
132                                 ret = p->ioprio;
133                         break;
134                 case IOPRIO_WHO_PGRP:
135                         if (!who)
136                                 who = process_group(current);
137                         do_each_task_pid(who, PIDTYPE_PGID, p) {
138                                 if (ret == -ESRCH)
139                                         ret = p->ioprio;
140                                 else
141                                         ret = ioprio_best(ret, p->ioprio);
142                         } while_each_task_pid(who, PIDTYPE_PGID, p);
143                         break;
144                 case IOPRIO_WHO_USER:
145                         if (!who)
146                                 user = current->user;
147                         else
148                                 user = find_user(who);
149
150                         if (!user)
151                                 break;
152
153                         do_each_thread(g, p) {
154                                 if (p->uid != user->uid)
155                                         continue;
156                                 if (ret == -ESRCH)
157                                         ret = p->ioprio;
158                                 else
159                                         ret = ioprio_best(ret, p->ioprio);
160                         } while_each_thread(g, p);
161
162                         if (who)
163                                 free_uid(user);
164                         break;
165                 default:
166                         ret = -EINVAL;
167         }
168
169         read_unlock_irq(&tasklist_lock);
170         return ret;
171 }
172