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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 | if (!who) | |
115 | p = current; | |
116 | else | |
117 | p = find_task_by_vpid(who); | |
118 | if (p) | |
119 | ret = set_task_ioprio(p, ioprio); | |
120 | break; | |
121 | case IOPRIO_WHO_PGRP: | |
122 | if (!who) | |
123 | pgrp = task_pgrp(current); | |
124 | else | |
125 | pgrp = find_vpid(who); | |
126 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { | |
127 | ret = set_task_ioprio(p, ioprio); | |
128 | if (ret) | |
129 | break; | |
130 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); | |
131 | break; | |
132 | case IOPRIO_WHO_USER: | |
133 | if (!who) | |
134 | user = current_user(); | |
135 | else | |
136 | user = find_user(who); | |
137 | ||
138 | if (!user) | |
139 | break; | |
140 | ||
141 | do_each_thread(g, p) { | |
142 | if (__task_cred(p)->uid != who) | |
143 | continue; | |
144 | ret = set_task_ioprio(p, ioprio); | |
145 | if (ret) | |
146 | goto free_uid; | |
147 | } while_each_thread(g, p); | |
148 | free_uid: | |
149 | if (who) | |
150 | free_uid(user); | |
151 | break; | |
152 | default: | |
153 | ret = -EINVAL; | |
154 | } | |
155 | ||
156 | read_unlock(&tasklist_lock); | |
157 | return ret; | |
158 | } | |
159 | ||
160 | static int get_task_ioprio(struct task_struct *p) | |
161 | { | |
162 | int ret; | |
163 | ||
164 | ret = security_task_getioprio(p); | |
165 | if (ret) | |
166 | goto out; | |
167 | ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); | |
168 | if (p->io_context) | |
169 | ret = p->io_context->ioprio; | |
170 | out: | |
171 | return ret; | |
172 | } | |
173 | ||
174 | int ioprio_best(unsigned short aprio, unsigned short bprio) | |
175 | { | |
176 | unsigned short aclass = IOPRIO_PRIO_CLASS(aprio); | |
177 | unsigned short bclass = IOPRIO_PRIO_CLASS(bprio); | |
178 | ||
179 | if (aclass == IOPRIO_CLASS_NONE) | |
180 | aclass = IOPRIO_CLASS_BE; | |
181 | if (bclass == IOPRIO_CLASS_NONE) | |
182 | bclass = IOPRIO_CLASS_BE; | |
183 | ||
184 | if (aclass == bclass) | |
185 | return min(aprio, bprio); | |
186 | if (aclass > bclass) | |
187 | return bprio; | |
188 | else | |
189 | return aprio; | |
190 | } | |
191 | ||
192 | SYSCALL_DEFINE2(ioprio_get, int, which, int, who) | |
193 | { | |
194 | struct task_struct *g, *p; | |
195 | struct user_struct *user; | |
196 | struct pid *pgrp; | |
197 | int ret = -ESRCH; | |
198 | int tmpio; | |
199 | ||
200 | read_lock(&tasklist_lock); | |
201 | switch (which) { | |
202 | case IOPRIO_WHO_PROCESS: | |
203 | if (!who) | |
204 | p = current; | |
205 | else | |
206 | p = find_task_by_vpid(who); | |
207 | if (p) | |
208 | ret = get_task_ioprio(p); | |
209 | break; | |
210 | case IOPRIO_WHO_PGRP: | |
211 | if (!who) | |
212 | pgrp = task_pgrp(current); | |
213 | else | |
214 | pgrp = find_vpid(who); | |
215 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { | |
216 | tmpio = get_task_ioprio(p); | |
217 | if (tmpio < 0) | |
218 | continue; | |
219 | if (ret == -ESRCH) | |
220 | ret = tmpio; | |
221 | else | |
222 | ret = ioprio_best(ret, tmpio); | |
223 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); | |
224 | break; | |
225 | case IOPRIO_WHO_USER: | |
226 | if (!who) | |
227 | user = current_user(); | |
228 | else | |
229 | user = find_user(who); | |
230 | ||
231 | if (!user) | |
232 | break; | |
233 | ||
234 | do_each_thread(g, p) { | |
235 | if (__task_cred(p)->uid != user->uid) | |
236 | continue; | |
237 | tmpio = get_task_ioprio(p); | |
238 | if (tmpio < 0) | |
239 | continue; | |
240 | if (ret == -ESRCH) | |
241 | ret = tmpio; | |
242 | else | |
243 | ret = ioprio_best(ret, tmpio); | |
244 | } while_each_thread(g, p); | |
245 | ||
246 | if (who) | |
247 | free_uid(user); | |
248 | break; | |
249 | default: | |
250 | ret = -EINVAL; | |
251 | } | |
252 | ||
253 | read_unlock(&tasklist_lock); | |
254 | return ret; | |
255 | } |