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22e2c507 JA |
1 | /* |
2 | * fs/ioprio.c | |
3 | * | |
0fe23479 | 4 | * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk> |
22e2c507 JA |
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 | */ | |
5a0e3ad6 | 22 | #include <linux/gfp.h> |
22e2c507 JA |
23 | #include <linux/kernel.h> |
24 | #include <linux/ioprio.h> | |
25 | #include <linux/blkdev.h> | |
16f7e0fe | 26 | #include <linux/capability.h> |
9abdc4cd | 27 | #include <linux/syscalls.h> |
03e68060 | 28 | #include <linux/security.h> |
b488893a | 29 | #include <linux/pid_namespace.h> |
22e2c507 | 30 | |
b3881f74 | 31 | int set_task_ioprio(struct task_struct *task, int ioprio) |
22e2c507 | 32 | { |
03e68060 | 33 | int err; |
22e2c507 | 34 | struct io_context *ioc; |
c69e8d9c | 35 | const struct cred *cred = current_cred(), *tcred; |
22e2c507 | 36 | |
c69e8d9c DH |
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(); | |
22e2c507 | 42 | return -EPERM; |
c69e8d9c DH |
43 | } |
44 | rcu_read_unlock(); | |
22e2c507 | 45 | |
03e68060 JM |
46 | err = security_task_setioprio(task, ioprio); |
47 | if (err) | |
48 | return err; | |
49 | ||
22e2c507 | 50 | task_lock(task); |
fd0928df JA |
51 | do { |
52 | ioc = task->io_context; | |
53 | /* see wmb() in current_io_context() */ | |
54 | smp_read_barrier_depends(); | |
55 | if (ioc) | |
56 | break; | |
22e2c507 | 57 | |
fd0928df JA |
58 | ioc = alloc_io_context(GFP_ATOMIC, -1); |
59 | if (!ioc) { | |
60 | err = -ENOMEM; | |
61 | break; | |
62 | } | |
63 | task->io_context = ioc; | |
fd0928df | 64 | } while (1); |
9f83e45e | 65 | |
fd0928df JA |
66 | if (!err) { |
67 | ioc->ioprio = ioprio; | |
fc46379d | 68 | ioc->ioprio_changed = 1; |
fd0928df | 69 | } |
22e2c507 JA |
70 | |
71 | task_unlock(task); | |
fd0928df | 72 | return err; |
22e2c507 | 73 | } |
b3881f74 | 74 | EXPORT_SYMBOL_GPL(set_task_ioprio); |
22e2c507 | 75 | |
938bb9f5 | 76 | SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) |
22e2c507 JA |
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; | |
41487c65 | 82 | struct pid *pgrp; |
22e2c507 JA |
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; | |
8ec680e4 JA |
97 | case IOPRIO_CLASS_NONE: |
98 | if (data) | |
99 | return -EINVAL; | |
100 | break; | |
22e2c507 JA |
101 | default: |
102 | return -EINVAL; | |
103 | } | |
104 | ||
105 | ret = -ESRCH; | |
cf342e52 ON |
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); | |
22e2c507 JA |
112 | switch (which) { |
113 | case IOPRIO_WHO_PROCESS: | |
114 | if (!who) | |
115 | p = current; | |
116 | else | |
228ebcbe | 117 | p = find_task_by_vpid(who); |
22e2c507 JA |
118 | if (p) |
119 | ret = set_task_ioprio(p, ioprio); | |
120 | break; | |
121 | case IOPRIO_WHO_PGRP: | |
122 | if (!who) | |
41487c65 EB |
123 | pgrp = task_pgrp(current); |
124 | else | |
b488893a | 125 | pgrp = find_vpid(who); |
2d70b68d | 126 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { |
22e2c507 JA |
127 | ret = set_task_ioprio(p, ioprio); |
128 | if (ret) | |
129 | break; | |
2d70b68d | 130 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); |
22e2c507 JA |
131 | break; |
132 | case IOPRIO_WHO_USER: | |
133 | if (!who) | |
86a264ab | 134 | user = current_user(); |
22e2c507 JA |
135 | else |
136 | user = find_user(who); | |
137 | ||
138 | if (!user) | |
139 | break; | |
140 | ||
141 | do_each_thread(g, p) { | |
1447399b DB |
142 | int match; |
143 | ||
144 | rcu_read_lock(); | |
145 | match = __task_cred(p)->uid == who; | |
146 | rcu_read_unlock(); | |
147 | if (!match) | |
22e2c507 JA |
148 | continue; |
149 | ret = set_task_ioprio(p, ioprio); | |
150 | if (ret) | |
78bd4d48 | 151 | goto free_uid; |
22e2c507 | 152 | } while_each_thread(g, p); |
78bd4d48 | 153 | free_uid: |
22e2c507 JA |
154 | if (who) |
155 | free_uid(user); | |
156 | break; | |
157 | default: | |
158 | ret = -EINVAL; | |
159 | } | |
160 | ||
cf342e52 | 161 | read_unlock(&tasklist_lock); |
22e2c507 JA |
162 | return ret; |
163 | } | |
164 | ||
a1836a42 DQ |
165 | static int get_task_ioprio(struct task_struct *p) |
166 | { | |
167 | int ret; | |
168 | ||
169 | ret = security_task_getioprio(p); | |
170 | if (ret) | |
171 | goto out; | |
fd0928df JA |
172 | ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); |
173 | if (p->io_context) | |
174 | ret = p->io_context->ioprio; | |
a1836a42 DQ |
175 | out: |
176 | return ret; | |
177 | } | |
178 | ||
e014ff8d ON |
179 | int ioprio_best(unsigned short aprio, unsigned short bprio) |
180 | { | |
181 | unsigned short aclass = IOPRIO_PRIO_CLASS(aprio); | |
182 | unsigned short bclass = IOPRIO_PRIO_CLASS(bprio); | |
183 | ||
e014ff8d ON |
184 | if (aclass == IOPRIO_CLASS_NONE) |
185 | aclass = IOPRIO_CLASS_BE; | |
186 | if (bclass == IOPRIO_CLASS_NONE) | |
187 | bclass = IOPRIO_CLASS_BE; | |
188 | ||
189 | if (aclass == bclass) | |
190 | return min(aprio, bprio); | |
191 | if (aclass > bclass) | |
192 | return bprio; | |
193 | else | |
194 | return aprio; | |
195 | } | |
196 | ||
938bb9f5 | 197 | SYSCALL_DEFINE2(ioprio_get, int, which, int, who) |
22e2c507 JA |
198 | { |
199 | struct task_struct *g, *p; | |
200 | struct user_struct *user; | |
41487c65 | 201 | struct pid *pgrp; |
22e2c507 | 202 | int ret = -ESRCH; |
a1836a42 | 203 | int tmpio; |
22e2c507 | 204 | |
cf342e52 | 205 | read_lock(&tasklist_lock); |
22e2c507 JA |
206 | switch (which) { |
207 | case IOPRIO_WHO_PROCESS: | |
208 | if (!who) | |
209 | p = current; | |
210 | else | |
228ebcbe | 211 | p = find_task_by_vpid(who); |
22e2c507 | 212 | if (p) |
a1836a42 | 213 | ret = get_task_ioprio(p); |
22e2c507 JA |
214 | break; |
215 | case IOPRIO_WHO_PGRP: | |
216 | if (!who) | |
41487c65 EB |
217 | pgrp = task_pgrp(current); |
218 | else | |
b488893a | 219 | pgrp = find_vpid(who); |
2d70b68d | 220 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { |
a1836a42 DQ |
221 | tmpio = get_task_ioprio(p); |
222 | if (tmpio < 0) | |
223 | continue; | |
22e2c507 | 224 | if (ret == -ESRCH) |
a1836a42 | 225 | ret = tmpio; |
22e2c507 | 226 | else |
a1836a42 | 227 | ret = ioprio_best(ret, tmpio); |
2d70b68d | 228 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); |
22e2c507 JA |
229 | break; |
230 | case IOPRIO_WHO_USER: | |
231 | if (!who) | |
86a264ab | 232 | user = current_user(); |
22e2c507 JA |
233 | else |
234 | user = find_user(who); | |
235 | ||
236 | if (!user) | |
237 | break; | |
238 | ||
239 | do_each_thread(g, p) { | |
1447399b DB |
240 | int match; |
241 | ||
242 | rcu_read_lock(); | |
243 | match = __task_cred(p)->uid == user->uid; | |
244 | rcu_read_unlock(); | |
245 | if (!match) | |
22e2c507 | 246 | continue; |
a1836a42 DQ |
247 | tmpio = get_task_ioprio(p); |
248 | if (tmpio < 0) | |
249 | continue; | |
22e2c507 | 250 | if (ret == -ESRCH) |
a1836a42 | 251 | ret = tmpio; |
22e2c507 | 252 | else |
a1836a42 | 253 | ret = ioprio_best(ret, tmpio); |
22e2c507 JA |
254 | } while_each_thread(g, p); |
255 | ||
256 | if (who) | |
257 | free_uid(user); | |
258 | break; | |
259 | default: | |
260 | ret = -EINVAL; | |
261 | } | |
262 | ||
cf342e52 | 263 | read_unlock(&tasklist_lock); |
22e2c507 JA |
264 | return ret; |
265 | } |