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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 | */ | |
22 | #include <linux/kernel.h> | |
23 | #include <linux/ioprio.h> | |
24 | #include <linux/blkdev.h> | |
16f7e0fe | 25 | #include <linux/capability.h> |
9abdc4cd | 26 | #include <linux/syscalls.h> |
03e68060 | 27 | #include <linux/security.h> |
b488893a | 28 | #include <linux/pid_namespace.h> |
22e2c507 JA |
29 | |
30 | static int set_task_ioprio(struct task_struct *task, int ioprio) | |
31 | { | |
03e68060 | 32 | int err; |
22e2c507 | 33 | struct io_context *ioc; |
c69e8d9c | 34 | const struct cred *cred = current_cred(), *tcred; |
22e2c507 | 35 | |
c69e8d9c DH |
36 | rcu_read_lock(); |
37 | tcred = __task_cred(task); | |
38 | if (tcred->uid != cred->euid && | |
39 | tcred->uid != cred->uid && !capable(CAP_SYS_NICE)) { | |
40 | rcu_read_unlock(); | |
22e2c507 | 41 | return -EPERM; |
c69e8d9c DH |
42 | } |
43 | rcu_read_unlock(); | |
22e2c507 | 44 | |
03e68060 JM |
45 | err = security_task_setioprio(task, ioprio); |
46 | if (err) | |
47 | return err; | |
48 | ||
22e2c507 | 49 | task_lock(task); |
fd0928df JA |
50 | do { |
51 | ioc = task->io_context; | |
52 | /* see wmb() in current_io_context() */ | |
53 | smp_read_barrier_depends(); | |
54 | if (ioc) | |
55 | break; | |
22e2c507 | 56 | |
fd0928df JA |
57 | ioc = alloc_io_context(GFP_ATOMIC, -1); |
58 | if (!ioc) { | |
59 | err = -ENOMEM; | |
60 | break; | |
61 | } | |
62 | task->io_context = ioc; | |
fd0928df | 63 | } while (1); |
9f83e45e | 64 | |
fd0928df JA |
65 | if (!err) { |
66 | ioc->ioprio = ioprio; | |
fc46379d | 67 | ioc->ioprio_changed = 1; |
fd0928df | 68 | } |
22e2c507 JA |
69 | |
70 | task_unlock(task); | |
fd0928df | 71 | return err; |
22e2c507 JA |
72 | } |
73 | ||
cf366808 | 74 | asmlinkage long sys_ioprio_set(int which, int who, int ioprio) |
22e2c507 JA |
75 | { |
76 | int class = IOPRIO_PRIO_CLASS(ioprio); | |
77 | int data = IOPRIO_PRIO_DATA(ioprio); | |
78 | struct task_struct *p, *g; | |
79 | struct user_struct *user; | |
41487c65 | 80 | struct pid *pgrp; |
22e2c507 JA |
81 | int ret; |
82 | ||
83 | switch (class) { | |
84 | case IOPRIO_CLASS_RT: | |
85 | if (!capable(CAP_SYS_ADMIN)) | |
86 | return -EPERM; | |
87 | /* fall through, rt has prio field too */ | |
88 | case IOPRIO_CLASS_BE: | |
89 | if (data >= IOPRIO_BE_NR || data < 0) | |
90 | return -EINVAL; | |
91 | ||
92 | break; | |
93 | case IOPRIO_CLASS_IDLE: | |
94 | break; | |
8ec680e4 JA |
95 | case IOPRIO_CLASS_NONE: |
96 | if (data) | |
97 | return -EINVAL; | |
98 | break; | |
22e2c507 JA |
99 | default: |
100 | return -EINVAL; | |
101 | } | |
102 | ||
103 | ret = -ESRCH; | |
cf342e52 ON |
104 | /* |
105 | * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic", | |
106 | * so we can't use rcu_read_lock(). See re-copy of ->ioprio | |
107 | * in copy_process(). | |
108 | */ | |
109 | read_lock(&tasklist_lock); | |
22e2c507 JA |
110 | switch (which) { |
111 | case IOPRIO_WHO_PROCESS: | |
112 | if (!who) | |
113 | p = current; | |
114 | else | |
228ebcbe | 115 | p = find_task_by_vpid(who); |
22e2c507 JA |
116 | if (p) |
117 | ret = set_task_ioprio(p, ioprio); | |
118 | break; | |
119 | case IOPRIO_WHO_PGRP: | |
120 | if (!who) | |
41487c65 EB |
121 | pgrp = task_pgrp(current); |
122 | else | |
b488893a | 123 | pgrp = find_vpid(who); |
2d70b68d | 124 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { |
22e2c507 JA |
125 | ret = set_task_ioprio(p, ioprio); |
126 | if (ret) | |
127 | break; | |
2d70b68d | 128 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); |
22e2c507 JA |
129 | break; |
130 | case IOPRIO_WHO_USER: | |
131 | if (!who) | |
86a264ab | 132 | user = current_user(); |
22e2c507 JA |
133 | else |
134 | user = find_user(who); | |
135 | ||
136 | if (!user) | |
137 | break; | |
138 | ||
139 | do_each_thread(g, p) { | |
c69e8d9c | 140 | if (__task_cred(p)->uid != who) |
22e2c507 JA |
141 | continue; |
142 | ret = set_task_ioprio(p, ioprio); | |
143 | if (ret) | |
78bd4d48 | 144 | goto free_uid; |
22e2c507 | 145 | } while_each_thread(g, p); |
78bd4d48 | 146 | free_uid: |
22e2c507 JA |
147 | if (who) |
148 | free_uid(user); | |
149 | break; | |
150 | default: | |
151 | ret = -EINVAL; | |
152 | } | |
153 | ||
cf342e52 | 154 | read_unlock(&tasklist_lock); |
22e2c507 JA |
155 | return ret; |
156 | } | |
157 | ||
a1836a42 DQ |
158 | static int get_task_ioprio(struct task_struct *p) |
159 | { | |
160 | int ret; | |
161 | ||
162 | ret = security_task_getioprio(p); | |
163 | if (ret) | |
164 | goto out; | |
fd0928df JA |
165 | ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); |
166 | if (p->io_context) | |
167 | ret = p->io_context->ioprio; | |
a1836a42 DQ |
168 | out: |
169 | return ret; | |
170 | } | |
171 | ||
e014ff8d ON |
172 | int ioprio_best(unsigned short aprio, unsigned short bprio) |
173 | { | |
174 | unsigned short aclass = IOPRIO_PRIO_CLASS(aprio); | |
175 | unsigned short bclass = IOPRIO_PRIO_CLASS(bprio); | |
176 | ||
e014ff8d ON |
177 | if (aclass == IOPRIO_CLASS_NONE) |
178 | aclass = IOPRIO_CLASS_BE; | |
179 | if (bclass == IOPRIO_CLASS_NONE) | |
180 | bclass = IOPRIO_CLASS_BE; | |
181 | ||
182 | if (aclass == bclass) | |
183 | return min(aprio, bprio); | |
184 | if (aclass > bclass) | |
185 | return bprio; | |
186 | else | |
187 | return aprio; | |
188 | } | |
189 | ||
cf366808 | 190 | asmlinkage long sys_ioprio_get(int which, int who) |
22e2c507 JA |
191 | { |
192 | struct task_struct *g, *p; | |
193 | struct user_struct *user; | |
41487c65 | 194 | struct pid *pgrp; |
22e2c507 | 195 | int ret = -ESRCH; |
a1836a42 | 196 | int tmpio; |
22e2c507 | 197 | |
cf342e52 | 198 | read_lock(&tasklist_lock); |
22e2c507 JA |
199 | switch (which) { |
200 | case IOPRIO_WHO_PROCESS: | |
201 | if (!who) | |
202 | p = current; | |
203 | else | |
228ebcbe | 204 | p = find_task_by_vpid(who); |
22e2c507 | 205 | if (p) |
a1836a42 | 206 | ret = get_task_ioprio(p); |
22e2c507 JA |
207 | break; |
208 | case IOPRIO_WHO_PGRP: | |
209 | if (!who) | |
41487c65 EB |
210 | pgrp = task_pgrp(current); |
211 | else | |
b488893a | 212 | pgrp = find_vpid(who); |
2d70b68d | 213 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { |
a1836a42 DQ |
214 | tmpio = get_task_ioprio(p); |
215 | if (tmpio < 0) | |
216 | continue; | |
22e2c507 | 217 | if (ret == -ESRCH) |
a1836a42 | 218 | ret = tmpio; |
22e2c507 | 219 | else |
a1836a42 | 220 | ret = ioprio_best(ret, tmpio); |
2d70b68d | 221 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); |
22e2c507 JA |
222 | break; |
223 | case IOPRIO_WHO_USER: | |
224 | if (!who) | |
86a264ab | 225 | user = current_user(); |
22e2c507 JA |
226 | else |
227 | user = find_user(who); | |
228 | ||
229 | if (!user) | |
230 | break; | |
231 | ||
232 | do_each_thread(g, p) { | |
c69e8d9c | 233 | if (__task_cred(p)->uid != user->uid) |
22e2c507 | 234 | continue; |
a1836a42 DQ |
235 | tmpio = get_task_ioprio(p); |
236 | if (tmpio < 0) | |
237 | continue; | |
22e2c507 | 238 | if (ret == -ESRCH) |
a1836a42 | 239 | ret = tmpio; |
22e2c507 | 240 | else |
a1836a42 | 241 | ret = ioprio_best(ret, tmpio); |
22e2c507 JA |
242 | } while_each_thread(g, p); |
243 | ||
244 | if (who) | |
245 | free_uid(user); | |
246 | break; | |
247 | default: | |
248 | ret = -EINVAL; | |
249 | } | |
250 | ||
cf342e52 | 251 | read_unlock(&tasklist_lock); |
22e2c507 JA |
252 | return ret; |
253 | } | |
254 |