Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[sfrench/cifs-2.6.git] / block / 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/cred.h>
27 #include <linux/blkdev.h>
28 #include <linux/capability.h>
29 #include <linux/sched/user.h>
30 #include <linux/sched/task.h>
31 #include <linux/syscalls.h>
32 #include <linux/security.h>
33 #include <linux/pid_namespace.h>
34
35 int set_task_ioprio(struct task_struct *task, int ioprio)
36 {
37         int err;
38         struct io_context *ioc;
39         const struct cred *cred = current_cred(), *tcred;
40
41         rcu_read_lock();
42         tcred = __task_cred(task);
43         if (!uid_eq(tcred->uid, cred->euid) &&
44             !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
45                 rcu_read_unlock();
46                 return -EPERM;
47         }
48         rcu_read_unlock();
49
50         err = security_task_setioprio(task, ioprio);
51         if (err)
52                 return err;
53
54         ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
55         if (ioc) {
56                 ioc->ioprio = ioprio;
57                 put_io_context(ioc);
58         }
59
60         return err;
61 }
62 EXPORT_SYMBOL_GPL(set_task_ioprio);
63
64 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
65 {
66         int class = IOPRIO_PRIO_CLASS(ioprio);
67         int data = IOPRIO_PRIO_DATA(ioprio);
68         struct task_struct *p, *g;
69         struct user_struct *user;
70         struct pid *pgrp;
71         kuid_t uid;
72         int ret;
73
74         switch (class) {
75                 case IOPRIO_CLASS_RT:
76                         if (!capable(CAP_SYS_ADMIN))
77                                 return -EPERM;
78                         /* fall through, rt has prio field too */
79                 case IOPRIO_CLASS_BE:
80                         if (data >= IOPRIO_BE_NR || data < 0)
81                                 return -EINVAL;
82
83                         break;
84                 case IOPRIO_CLASS_IDLE:
85                         break;
86                 case IOPRIO_CLASS_NONE:
87                         if (data)
88                                 return -EINVAL;
89                         break;
90                 default:
91                         return -EINVAL;
92         }
93
94         ret = -ESRCH;
95         rcu_read_lock();
96         switch (which) {
97                 case IOPRIO_WHO_PROCESS:
98                         if (!who)
99                                 p = current;
100                         else
101                                 p = find_task_by_vpid(who);
102                         if (p)
103                                 ret = set_task_ioprio(p, ioprio);
104                         break;
105                 case IOPRIO_WHO_PGRP:
106                         if (!who)
107                                 pgrp = task_pgrp(current);
108                         else
109                                 pgrp = find_vpid(who);
110                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
111                                 ret = set_task_ioprio(p, ioprio);
112                                 if (ret)
113                                         break;
114                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
115                         break;
116                 case IOPRIO_WHO_USER:
117                         uid = make_kuid(current_user_ns(), who);
118                         if (!uid_valid(uid))
119                                 break;
120                         if (!who)
121                                 user = current_user();
122                         else
123                                 user = find_user(uid);
124
125                         if (!user)
126                                 break;
127
128                         for_each_process_thread(g, p) {
129                                 if (!uid_eq(task_uid(p), uid) ||
130                                     !task_pid_vnr(p))
131                                         continue;
132                                 ret = set_task_ioprio(p, ioprio);
133                                 if (ret)
134                                         goto free_uid;
135                         }
136 free_uid:
137                         if (who)
138                                 free_uid(user);
139                         break;
140                 default:
141                         ret = -EINVAL;
142         }
143
144         rcu_read_unlock();
145         return ret;
146 }
147
148 static int get_task_ioprio(struct task_struct *p)
149 {
150         int ret;
151
152         ret = security_task_getioprio(p);
153         if (ret)
154                 goto out;
155         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
156         task_lock(p);
157         if (p->io_context)
158                 ret = p->io_context->ioprio;
159         task_unlock(p);
160 out:
161         return ret;
162 }
163
164 int ioprio_best(unsigned short aprio, unsigned short bprio)
165 {
166         unsigned short aclass;
167         unsigned short bclass;
168
169         if (!ioprio_valid(aprio))
170                 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
171         if (!ioprio_valid(bprio))
172                 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
173
174         aclass = IOPRIO_PRIO_CLASS(aprio);
175         bclass = IOPRIO_PRIO_CLASS(bprio);
176         if (aclass == bclass)
177                 return min(aprio, bprio);
178         if (aclass > bclass)
179                 return bprio;
180         else
181                 return aprio;
182 }
183
184 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
185 {
186         struct task_struct *g, *p;
187         struct user_struct *user;
188         struct pid *pgrp;
189         kuid_t uid;
190         int ret = -ESRCH;
191         int tmpio;
192
193         rcu_read_lock();
194         switch (which) {
195                 case IOPRIO_WHO_PROCESS:
196                         if (!who)
197                                 p = current;
198                         else
199                                 p = find_task_by_vpid(who);
200                         if (p)
201                                 ret = get_task_ioprio(p);
202                         break;
203                 case IOPRIO_WHO_PGRP:
204                         if (!who)
205                                 pgrp = task_pgrp(current);
206                         else
207                                 pgrp = find_vpid(who);
208                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
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_pid_thread(pgrp, PIDTYPE_PGID, p);
217                         break;
218                 case IOPRIO_WHO_USER:
219                         uid = make_kuid(current_user_ns(), who);
220                         if (!who)
221                                 user = current_user();
222                         else
223                                 user = find_user(uid);
224
225                         if (!user)
226                                 break;
227
228                         for_each_process_thread(g, p) {
229                                 if (!uid_eq(task_uid(p), user->uid) ||
230                                     !task_pid_vnr(p))
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                         }
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 }