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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/cred.h> | |
27 | #include <linux/blkdev.h> | |
28 | #include <linux/capability.h> | |
29 | #include <linux/sched/user.h> | |
30 | #include <linux/sched/task.h> | |
31 | #include <linux/syscalls.h> | |
32 | #include <linux/security.h> | |
33 | #include <linux/pid_namespace.h> | |
34 | ||
35 | int set_task_ioprio(struct task_struct *task, int ioprio) | |
36 | { | |
37 | int err; | |
38 | struct io_context *ioc; | |
39 | const struct cred *cred = current_cred(), *tcred; | |
40 | ||
41 | rcu_read_lock(); | |
42 | tcred = __task_cred(task); | |
43 | if (!uid_eq(tcred->uid, cred->euid) && | |
44 | !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) { | |
45 | rcu_read_unlock(); | |
46 | return -EPERM; | |
47 | } | |
48 | rcu_read_unlock(); | |
49 | ||
50 | err = security_task_setioprio(task, ioprio); | |
51 | if (err) | |
52 | return err; | |
53 | ||
54 | ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE); | |
55 | if (ioc) { | |
56 | ioc->ioprio = ioprio; | |
57 | put_io_context(ioc); | |
58 | } | |
59 | ||
60 | return err; | |
61 | } | |
62 | EXPORT_SYMBOL_GPL(set_task_ioprio); | |
63 | ||
64 | SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) | |
65 | { | |
66 | int class = IOPRIO_PRIO_CLASS(ioprio); | |
67 | int data = IOPRIO_PRIO_DATA(ioprio); | |
68 | struct task_struct *p, *g; | |
69 | struct user_struct *user; | |
70 | struct pid *pgrp; | |
71 | kuid_t uid; | |
72 | int ret; | |
73 | ||
74 | switch (class) { | |
75 | case IOPRIO_CLASS_RT: | |
76 | if (!capable(CAP_SYS_ADMIN)) | |
77 | return -EPERM; | |
78 | /* fall through */ | |
79 | /* rt has prio field too */ | |
80 | case IOPRIO_CLASS_BE: | |
81 | if (data >= IOPRIO_BE_NR || data < 0) | |
82 | return -EINVAL; | |
83 | ||
84 | break; | |
85 | case IOPRIO_CLASS_IDLE: | |
86 | break; | |
87 | case IOPRIO_CLASS_NONE: | |
88 | if (data) | |
89 | return -EINVAL; | |
90 | break; | |
91 | default: | |
92 | return -EINVAL; | |
93 | } | |
94 | ||
95 | ret = -ESRCH; | |
96 | rcu_read_lock(); | |
97 | switch (which) { | |
98 | case IOPRIO_WHO_PROCESS: | |
99 | if (!who) | |
100 | p = current; | |
101 | else | |
102 | p = find_task_by_vpid(who); | |
103 | if (p) | |
104 | ret = set_task_ioprio(p, ioprio); | |
105 | break; | |
106 | case IOPRIO_WHO_PGRP: | |
107 | if (!who) | |
108 | pgrp = task_pgrp(current); | |
109 | else | |
110 | pgrp = find_vpid(who); | |
111 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { | |
112 | ret = set_task_ioprio(p, ioprio); | |
113 | if (ret) | |
114 | break; | |
115 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); | |
116 | break; | |
117 | case IOPRIO_WHO_USER: | |
118 | uid = make_kuid(current_user_ns(), who); | |
119 | if (!uid_valid(uid)) | |
120 | break; | |
121 | if (!who) | |
122 | user = current_user(); | |
123 | else | |
124 | user = find_user(uid); | |
125 | ||
126 | if (!user) | |
127 | break; | |
128 | ||
129 | for_each_process_thread(g, p) { | |
130 | if (!uid_eq(task_uid(p), uid) || | |
131 | !task_pid_vnr(p)) | |
132 | continue; | |
133 | ret = set_task_ioprio(p, ioprio); | |
134 | if (ret) | |
135 | goto free_uid; | |
136 | } | |
137 | free_uid: | |
138 | if (who) | |
139 | free_uid(user); | |
140 | break; | |
141 | default: | |
142 | ret = -EINVAL; | |
143 | } | |
144 | ||
145 | rcu_read_unlock(); | |
146 | return ret; | |
147 | } | |
148 | ||
149 | static int get_task_ioprio(struct task_struct *p) | |
150 | { | |
151 | int ret; | |
152 | ||
153 | ret = security_task_getioprio(p); | |
154 | if (ret) | |
155 | goto out; | |
156 | ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); | |
157 | task_lock(p); | |
158 | if (p->io_context) | |
159 | ret = p->io_context->ioprio; | |
160 | task_unlock(p); | |
161 | out: | |
162 | return ret; | |
163 | } | |
164 | ||
165 | int ioprio_best(unsigned short aprio, unsigned short bprio) | |
166 | { | |
167 | if (!ioprio_valid(aprio)) | |
168 | aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); | |
169 | if (!ioprio_valid(bprio)) | |
170 | bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); | |
171 | ||
172 | return min(aprio, bprio); | |
173 | } | |
174 | ||
175 | SYSCALL_DEFINE2(ioprio_get, int, which, int, who) | |
176 | { | |
177 | struct task_struct *g, *p; | |
178 | struct user_struct *user; | |
179 | struct pid *pgrp; | |
180 | kuid_t uid; | |
181 | int ret = -ESRCH; | |
182 | int tmpio; | |
183 | ||
184 | rcu_read_lock(); | |
185 | switch (which) { | |
186 | case IOPRIO_WHO_PROCESS: | |
187 | if (!who) | |
188 | p = current; | |
189 | else | |
190 | p = find_task_by_vpid(who); | |
191 | if (p) | |
192 | ret = get_task_ioprio(p); | |
193 | break; | |
194 | case IOPRIO_WHO_PGRP: | |
195 | if (!who) | |
196 | pgrp = task_pgrp(current); | |
197 | else | |
198 | pgrp = find_vpid(who); | |
199 | do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { | |
200 | tmpio = get_task_ioprio(p); | |
201 | if (tmpio < 0) | |
202 | continue; | |
203 | if (ret == -ESRCH) | |
204 | ret = tmpio; | |
205 | else | |
206 | ret = ioprio_best(ret, tmpio); | |
207 | } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); | |
208 | break; | |
209 | case IOPRIO_WHO_USER: | |
210 | uid = make_kuid(current_user_ns(), who); | |
211 | if (!who) | |
212 | user = current_user(); | |
213 | else | |
214 | user = find_user(uid); | |
215 | ||
216 | if (!user) | |
217 | break; | |
218 | ||
219 | for_each_process_thread(g, p) { | |
220 | if (!uid_eq(task_uid(p), user->uid) || | |
221 | !task_pid_vnr(p)) | |
222 | continue; | |
223 | tmpio = get_task_ioprio(p); | |
224 | if (tmpio < 0) | |
225 | continue; | |
226 | if (ret == -ESRCH) | |
227 | ret = tmpio; | |
228 | else | |
229 | ret = ioprio_best(ret, tmpio); | |
230 | } | |
231 | ||
232 | if (who) | |
233 | free_uid(user); | |
234 | break; | |
235 | default: | |
236 | ret = -EINVAL; | |
237 | } | |
238 | ||
239 | rcu_read_unlock(); | |
240 | return ret; | |
241 | } |