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