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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/ioprio.h> | |
25 | #include <linux/blkdev.h> | |
26 | #include <linux/capability.h> | |
27 | #include <linux/syscalls.h> | |
28 | #include <linux/security.h> | |
29 | #include <linux/pid_namespace.h> | |
30 | ||
31 | int set_task_ioprio(struct task_struct *task, int ioprio) | |
32 | { | |
33 | int err; | |
34 | struct io_context *ioc; | |
35 | const struct cred *cred = current_cred(), *tcred; | |
36 | ||
37 | rcu_read_lock(); | |
38 | tcred = __task_cred(task); | |
39 | if (tcred->uid != cred->euid && | |
40 | tcred->uid != cred->uid && !capable(CAP_SYS_NICE)) { | |
41 | rcu_read_unlock(); | |
42 | return -EPERM; | |
43 | } | |
44 | rcu_read_unlock(); | |
45 | ||
46 | err = security_task_setioprio(task, ioprio); | |
47 | if (err) | |
48 | return err; | |
49 | ||
50 | task_lock(task); | |
51 | do { | |
52 | ioc = task->io_context; | |
53 | /* see wmb() in current_io_context() */ | |
54 | smp_read_barrier_depends(); | |
55 | if (ioc) | |
56 | break; | |
57 | ||
58 | ioc = alloc_io_context(GFP_ATOMIC, -1); | |
59 | if (!ioc) { | |
60 | err = -ENOMEM; | |
61 | break; | |
62 | } | |
63 | task->io_context = ioc; | |
64 | } while (1); | |
65 | ||
66 | if (!err) { | |
67 | ioc->ioprio = ioprio; | |
68 | ioc->ioprio_changed = 1; | |
69 | } | |
70 | ||
71 | task_unlock(task); | |
72 | return err; | |
73 | } | |
74 | EXPORT_SYMBOL_GPL(set_task_ioprio); | |
75 | ||
76 | SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) | |
77 | { | |
78 | int class = IOPRIO_PRIO_CLASS(ioprio); | |
79 | int data = IOPRIO_PRIO_DATA(ioprio); | |
80 | struct task_struct *p, *g; | |
81 | struct user_struct *user; | |
82 | struct pid *pgrp; | |
83 | int ret; | |
84 | ||
85 | switch (class) { | |
86 | case IOPRIO_CLASS_RT: | |
87 | if (!capable(CAP_SYS_ADMIN)) | |
88 | return -EPERM; | |
89 | /* fall through, rt has prio field too */ | |
90 | case IOPRIO_CLASS_BE: | |
91 | if (data >= IOPRIO_BE_NR || data < 0) | |
92 | return -EINVAL; | |
93 | ||
94 | break; | |
95 | case IOPRIO_CLASS_IDLE: | |
96 | break; | |
97 | case IOPRIO_CLASS_NONE: | |
98 | if (data) | |
99 | return -EINVAL; | |
100 | break; | |
101 | default: | |
102 | return -EINVAL; | |
103 | } | |
104 | ||
105 | ret = -ESRCH; | |
106 | /* | |
107 | * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic", | |
108 | * so we can't use rcu_read_lock(). See re-copy of ->ioprio | |
109 | * in copy_process(). | |
110 | */ | |
111 | read_lock(&tasklist_lock); | |
112 | switch (which) { | |
113 | case IOPRIO_WHO_PROCESS: | |
114 | rcu_read_lock(); | |
115 | if (!who) | |
116 | p = current; | |
117 | else | |
118 | p = find_task_by_vpid(who); | |
119 | if (p) | |
120 | ret = set_task_ioprio(p, ioprio); | |
121 | rcu_read_unlock(); | |
122 | break; | |
123 | case IOPRIO_WHO_PGRP: | |
124 | if (!who) | |
125 | pgrp = task_pgrp(current); | |
126 | else | |
127 | pgrp = find_vpid(who); | |
128 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { | |
129 | ret = set_task_ioprio(p, ioprio); | |
130 | if (ret) | |
131 | break; | |
132 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); | |
133 | break; | |
134 | case IOPRIO_WHO_USER: | |
135 | if (!who) | |
136 | user = current_user(); | |
137 | else | |
138 | user = find_user(who); | |
139 | ||
140 | if (!user) | |
141 | break; | |
142 | ||
143 | do_each_thread(g, p) { | |
144 | int match; | |
145 | ||
146 | rcu_read_lock(); | |
147 | match = __task_cred(p)->uid == who; | |
148 | rcu_read_unlock(); | |
149 | if (!match) | |
150 | continue; | |
151 | ret = set_task_ioprio(p, ioprio); | |
152 | if (ret) | |
153 | goto free_uid; | |
154 | } while_each_thread(g, p); | |
155 | free_uid: | |
156 | if (who) | |
157 | free_uid(user); | |
158 | break; | |
159 | default: | |
160 | ret = -EINVAL; | |
161 | } | |
162 | ||
163 | read_unlock(&tasklist_lock); | |
164 | return ret; | |
165 | } | |
166 | ||
167 | static int get_task_ioprio(struct task_struct *p) | |
168 | { | |
169 | int ret; | |
170 | ||
171 | ret = security_task_getioprio(p); | |
172 | if (ret) | |
173 | goto out; | |
174 | ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); | |
175 | if (p->io_context) | |
176 | ret = p->io_context->ioprio; | |
177 | out: | |
178 | return ret; | |
179 | } | |
180 | ||
181 | int ioprio_best(unsigned short aprio, unsigned short bprio) | |
182 | { | |
183 | unsigned short aclass = IOPRIO_PRIO_CLASS(aprio); | |
184 | unsigned short bclass = IOPRIO_PRIO_CLASS(bprio); | |
185 | ||
186 | if (aclass == IOPRIO_CLASS_NONE) | |
187 | aclass = IOPRIO_CLASS_BE; | |
188 | if (bclass == IOPRIO_CLASS_NONE) | |
189 | bclass = IOPRIO_CLASS_BE; | |
190 | ||
191 | if (aclass == bclass) | |
192 | return min(aprio, bprio); | |
193 | if (aclass > bclass) | |
194 | return bprio; | |
195 | else | |
196 | return aprio; | |
197 | } | |
198 | ||
199 | SYSCALL_DEFINE2(ioprio_get, int, which, int, who) | |
200 | { | |
201 | struct task_struct *g, *p; | |
202 | struct user_struct *user; | |
203 | struct pid *pgrp; | |
204 | int ret = -ESRCH; | |
205 | int tmpio; | |
206 | ||
207 | read_lock(&tasklist_lock); | |
208 | switch (which) { | |
209 | case IOPRIO_WHO_PROCESS: | |
210 | rcu_read_lock(); | |
211 | if (!who) | |
212 | p = current; | |
213 | else | |
214 | p = find_task_by_vpid(who); | |
215 | if (p) | |
216 | ret = get_task_ioprio(p); | |
217 | rcu_read_unlock(); | |
218 | break; | |
219 | case IOPRIO_WHO_PGRP: | |
220 | if (!who) | |
221 | pgrp = task_pgrp(current); | |
222 | else | |
223 | pgrp = find_vpid(who); | |
224 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { | |
225 | tmpio = get_task_ioprio(p); | |
226 | if (tmpio < 0) | |
227 | continue; | |
228 | if (ret == -ESRCH) | |
229 | ret = tmpio; | |
230 | else | |
231 | ret = ioprio_best(ret, tmpio); | |
232 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); | |
233 | break; | |
234 | case IOPRIO_WHO_USER: | |
235 | if (!who) | |
236 | user = current_user(); | |
237 | else | |
238 | user = find_user(who); | |
239 | ||
240 | if (!user) | |
241 | break; | |
242 | ||
243 | do_each_thread(g, p) { | |
244 | int match; | |
245 | ||
246 | rcu_read_lock(); | |
247 | match = __task_cred(p)->uid == user->uid; | |
248 | rcu_read_unlock(); | |
249 | if (!match) | |
250 | continue; | |
251 | tmpio = get_task_ioprio(p); | |
252 | if (tmpio < 0) | |
253 | continue; | |
254 | if (ret == -ESRCH) | |
255 | ret = tmpio; | |
256 | else | |
257 | ret = ioprio_best(ret, tmpio); | |
258 | } while_each_thread(g, p); | |
259 | ||
260 | if (who) | |
261 | free_uid(user); | |
262 | break; | |
263 | default: | |
264 | ret = -EINVAL; | |
265 | } | |
266 | ||
267 | read_unlock(&tasklist_lock); | |
268 | return ret; | |
269 | } |