[PATCH] pid: replace do/while_each_task_pid with do/while_each_pid_task
[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/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
29 static int set_task_ioprio(struct task_struct *task, int ioprio)
30 {
31         int err;
32         struct io_context *ioc;
33
34         if (task->uid != current->euid &&
35             task->uid != current->uid && !capable(CAP_SYS_NICE))
36                 return -EPERM;
37
38         err = security_task_setioprio(task, ioprio);
39         if (err)
40                 return err;
41
42         task_lock(task);
43
44         task->ioprio = ioprio;
45
46         ioc = task->io_context;
47         /* see wmb() in current_io_context() */
48         smp_read_barrier_depends();
49
50         if (ioc)
51                 ioc->ioprio_changed = 1;
52
53         task_unlock(task);
54         return 0;
55 }
56
57 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
58 {
59         int class = IOPRIO_PRIO_CLASS(ioprio);
60         int data = IOPRIO_PRIO_DATA(ioprio);
61         struct task_struct *p, *g;
62         struct user_struct *user;
63         struct pid *pgrp;
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         /*
86          * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
87          * so we can't use rcu_read_lock(). See re-copy of ->ioprio
88          * in copy_process().
89          */
90         read_lock(&tasklist_lock);
91         switch (which) {
92                 case IOPRIO_WHO_PROCESS:
93                         if (!who)
94                                 p = current;
95                         else
96                                 p = find_task_by_pid(who);
97                         if (p)
98                                 ret = set_task_ioprio(p, ioprio);
99                         break;
100                 case IOPRIO_WHO_PGRP:
101                         if (!who)
102                                 pgrp = task_pgrp(current);
103                         else
104                                 pgrp = find_pid(who);
105                         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
106                                 ret = set_task_ioprio(p, ioprio);
107                                 if (ret)
108                                         break;
109                         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
110                         break;
111                 case IOPRIO_WHO_USER:
112                         if (!who)
113                                 user = current->user;
114                         else
115                                 user = find_user(who);
116
117                         if (!user)
118                                 break;
119
120                         do_each_thread(g, p) {
121                                 if (p->uid != who)
122                                         continue;
123                                 ret = set_task_ioprio(p, ioprio);
124                                 if (ret)
125                                         goto free_uid;
126                         } while_each_thread(g, p);
127 free_uid:
128                         if (who)
129                                 free_uid(user);
130                         break;
131                 default:
132                         ret = -EINVAL;
133         }
134
135         read_unlock(&tasklist_lock);
136         return ret;
137 }
138
139 static int get_task_ioprio(struct task_struct *p)
140 {
141         int ret;
142
143         ret = security_task_getioprio(p);
144         if (ret)
145                 goto out;
146         ret = p->ioprio;
147 out:
148         return ret;
149 }
150
151 int ioprio_best(unsigned short aprio, unsigned short bprio)
152 {
153         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
154         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
155
156         if (aclass == IOPRIO_CLASS_NONE)
157                 aclass = IOPRIO_CLASS_BE;
158         if (bclass == IOPRIO_CLASS_NONE)
159                 bclass = IOPRIO_CLASS_BE;
160
161         if (aclass == bclass)
162                 return min(aprio, bprio);
163         if (aclass > bclass)
164                 return bprio;
165         else
166                 return aprio;
167 }
168
169 asmlinkage long sys_ioprio_get(int which, int who)
170 {
171         struct task_struct *g, *p;
172         struct user_struct *user;
173         struct pid *pgrp;
174         int ret = -ESRCH;
175         int tmpio;
176
177         read_lock(&tasklist_lock);
178         switch (which) {
179                 case IOPRIO_WHO_PROCESS:
180                         if (!who)
181                                 p = current;
182                         else
183                                 p = find_task_by_pid(who);
184                         if (p)
185                                 ret = get_task_ioprio(p);
186                         break;
187                 case IOPRIO_WHO_PGRP:
188                         if (!who)
189                                 pgrp = task_pgrp(current);
190                         else
191                                 pgrp = find_pid(who);
192                         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
193                                 tmpio = get_task_ioprio(p);
194                                 if (tmpio < 0)
195                                         continue;
196                                 if (ret == -ESRCH)
197                                         ret = tmpio;
198                                 else
199                                         ret = ioprio_best(ret, tmpio);
200                         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
201                         break;
202                 case IOPRIO_WHO_USER:
203                         if (!who)
204                                 user = current->user;
205                         else
206                                 user = find_user(who);
207
208                         if (!user)
209                                 break;
210
211                         do_each_thread(g, p) {
212                                 if (p->uid != user->uid)
213                                         continue;
214                                 tmpio = get_task_ioprio(p);
215                                 if (tmpio < 0)
216                                         continue;
217                                 if (ret == -ESRCH)
218                                         ret = tmpio;
219                                 else
220                                         ret = ioprio_best(ret, tmpio);
221                         } while_each_thread(g, p);
222
223                         if (who)
224                                 free_uid(user);
225                         break;
226                 default:
227                         ret = -EINVAL;
228         }
229
230         read_unlock(&tasklist_lock);
231         return ret;
232 }
233