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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/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 | } |
252 |
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