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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 | } |
256 |
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