Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input
[platform/adaptation/renesas_rcar/renesas_kernel.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 (tcred->uid != cred->euid &&
41             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         task_lock(task);
52         do {
53                 ioc = task->io_context;
54                 /* see wmb() in current_io_context() */
55                 smp_read_barrier_depends();
56                 if (ioc)
57                         break;
58
59                 ioc = alloc_io_context(GFP_ATOMIC, -1);
60                 if (!ioc) {
61                         err = -ENOMEM;
62                         break;
63                 }
64                 task->io_context = ioc;
65         } while (1);
66
67         if (!err) {
68                 ioc->ioprio = ioprio;
69                 ioc->ioprio_changed = 1;
70         }
71
72         task_unlock(task);
73         return err;
74 }
75 EXPORT_SYMBOL_GPL(set_task_ioprio);
76
77 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
78 {
79         int class = IOPRIO_PRIO_CLASS(ioprio);
80         int data = IOPRIO_PRIO_DATA(ioprio);
81         struct task_struct *p, *g;
82         struct user_struct *user;
83         struct pid *pgrp;
84         int ret;
85
86         switch (class) {
87                 case IOPRIO_CLASS_RT:
88                         if (!capable(CAP_SYS_ADMIN))
89                                 return -EPERM;
90                         /* fall through, rt has prio field too */
91                 case IOPRIO_CLASS_BE:
92                         if (data >= IOPRIO_BE_NR || data < 0)
93                                 return -EINVAL;
94
95                         break;
96                 case IOPRIO_CLASS_IDLE:
97                         break;
98                 case IOPRIO_CLASS_NONE:
99                         if (data)
100                                 return -EINVAL;
101                         break;
102                 default:
103                         return -EINVAL;
104         }
105
106         ret = -ESRCH;
107         rcu_read_lock();
108         switch (which) {
109                 case IOPRIO_WHO_PROCESS:
110                         if (!who)
111                                 p = current;
112                         else
113                                 p = find_task_by_vpid(who);
114                         if (p)
115                                 ret = set_task_ioprio(p, ioprio);
116                         break;
117                 case IOPRIO_WHO_PGRP:
118                         if (!who)
119                                 pgrp = task_pgrp(current);
120                         else
121                                 pgrp = find_vpid(who);
122                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
123                                 ret = set_task_ioprio(p, ioprio);
124                                 if (ret)
125                                         break;
126                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
127                         break;
128                 case IOPRIO_WHO_USER:
129                         if (!who)
130                                 user = current_user();
131                         else
132                                 user = find_user(who);
133
134                         if (!user)
135                                 break;
136
137                         do_each_thread(g, p) {
138                                 if (__task_cred(p)->uid != who)
139                                         continue;
140                                 ret = set_task_ioprio(p, ioprio);
141                                 if (ret)
142                                         goto free_uid;
143                         } while_each_thread(g, p);
144 free_uid:
145                         if (who)
146                                 free_uid(user);
147                         break;
148                 default:
149                         ret = -EINVAL;
150         }
151
152         rcu_read_unlock();
153         return ret;
154 }
155
156 static int get_task_ioprio(struct task_struct *p)
157 {
158         int ret;
159
160         ret = security_task_getioprio(p);
161         if (ret)
162                 goto out;
163         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
164         if (p->io_context)
165                 ret = p->io_context->ioprio;
166 out:
167         return ret;
168 }
169
170 int ioprio_best(unsigned short aprio, unsigned short bprio)
171 {
172         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
173         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
174
175         if (aclass == IOPRIO_CLASS_NONE)
176                 aclass = IOPRIO_CLASS_BE;
177         if (bclass == IOPRIO_CLASS_NONE)
178                 bclass = IOPRIO_CLASS_BE;
179
180         if (aclass == bclass)
181                 return min(aprio, bprio);
182         if (aclass > bclass)
183                 return bprio;
184         else
185                 return aprio;
186 }
187
188 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
189 {
190         struct task_struct *g, *p;
191         struct user_struct *user;
192         struct pid *pgrp;
193         int ret = -ESRCH;
194         int tmpio;
195
196         rcu_read_lock();
197         switch (which) {
198                 case IOPRIO_WHO_PROCESS:
199                         if (!who)
200                                 p = current;
201                         else
202                                 p = find_task_by_vpid(who);
203                         if (p)
204                                 ret = get_task_ioprio(p);
205                         break;
206                 case IOPRIO_WHO_PGRP:
207                         if (!who)
208                                 pgrp = task_pgrp(current);
209                         else
210                                 pgrp = find_vpid(who);
211                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
212                                 tmpio = get_task_ioprio(p);
213                                 if (tmpio < 0)
214                                         continue;
215                                 if (ret == -ESRCH)
216                                         ret = tmpio;
217                                 else
218                                         ret = ioprio_best(ret, tmpio);
219                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
220                         break;
221                 case IOPRIO_WHO_USER:
222                         if (!who)
223                                 user = current_user();
224                         else
225                                 user = find_user(who);
226
227                         if (!user)
228                                 break;
229
230                         do_each_thread(g, p) {
231                                 if (__task_cred(p)->uid != user->uid)
232                                         continue;
233                                 tmpio = get_task_ioprio(p);
234                                 if (tmpio < 0)
235                                         continue;
236                                 if (ret == -ESRCH)
237                                         ret = tmpio;
238                                 else
239                                         ret = ioprio_best(ret, tmpio);
240                         } while_each_thread(g, p);
241
242                         if (who)
243                                 free_uid(user);
244                         break;
245                 default:
246                         ret = -EINVAL;
247         }
248
249         rcu_read_unlock();
250         return ret;
251 }