Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * fs/ioprio.c
4 : *
5 : * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
6 : *
7 : * Helper functions for setting/querying io priorities of processes. The
8 : * system calls closely mimmick getpriority/setpriority, see the man page for
9 : * those. The prio argument is a composite of prio class and prio data, where
10 : * the data argument has meaning within that class. The standard scheduling
11 : * classes have 8 distinct prio levels, with 0 being the highest prio and 7
12 : * being the lowest.
13 : *
14 : * IOW, setting BE scheduling class with prio 2 is done ala:
15 : *
16 : * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
17 : *
18 : * ioprio_set(PRIO_PROCESS, pid, prio);
19 : *
20 : * See also Documentation/block/ioprio.rst
21 : *
22 : */
23 : #include <linux/gfp.h>
24 : #include <linux/kernel.h>
25 : #include <linux/export.h>
26 : #include <linux/ioprio.h>
27 : #include <linux/cred.h>
28 : #include <linux/blkdev.h>
29 : #include <linux/capability.h>
30 : #include <linux/sched/user.h>
31 : #include <linux/sched/task.h>
32 : #include <linux/syscalls.h>
33 : #include <linux/security.h>
34 : #include <linux/pid_namespace.h>
35 :
36 6 : int set_task_ioprio(struct task_struct *task, int ioprio)
37 : {
38 6 : int err;
39 6 : struct io_context *ioc;
40 6 : const struct cred *cred = current_cred(), *tcred;
41 :
42 6 : rcu_read_lock();
43 6 : tcred = __task_cred(task);
44 6 : if (!uid_eq(tcred->uid, cred->euid) &&
45 0 : !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
46 0 : rcu_read_unlock();
47 0 : return -EPERM;
48 : }
49 6 : rcu_read_unlock();
50 :
51 6 : err = security_task_setioprio(task, ioprio);
52 6 : if (err)
53 : return err;
54 :
55 6 : ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
56 6 : if (ioc) {
57 6 : ioc->ioprio = ioprio;
58 6 : put_io_context(ioc);
59 : }
60 :
61 : return err;
62 : }
63 : EXPORT_SYMBOL_GPL(set_task_ioprio);
64 :
65 4 : int ioprio_check_cap(int ioprio)
66 : {
67 4 : int class = IOPRIO_PRIO_CLASS(ioprio);
68 4 : int data = IOPRIO_PRIO_DATA(ioprio);
69 :
70 4 : switch (class) {
71 0 : case IOPRIO_CLASS_RT:
72 0 : if (!capable(CAP_SYS_NICE) && !capable(CAP_SYS_ADMIN))
73 : return -EPERM;
74 1 : fallthrough;
75 : /* rt has prio field too */
76 : case IOPRIO_CLASS_BE:
77 1 : if (data >= IOPRIO_BE_NR || data < 0)
78 0 : return -EINVAL;
79 :
80 : break;
81 : case IOPRIO_CLASS_IDLE:
82 : break;
83 0 : case IOPRIO_CLASS_NONE:
84 0 : if (data)
85 0 : return -EINVAL;
86 : break;
87 : default:
88 : return -EINVAL;
89 : }
90 :
91 : return 0;
92 : }
93 :
94 8 : SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
95 : {
96 4 : struct task_struct *p, *g;
97 4 : struct user_struct *user;
98 4 : struct pid *pgrp;
99 4 : kuid_t uid;
100 4 : int ret;
101 :
102 4 : ret = ioprio_check_cap(ioprio);
103 4 : if (ret)
104 0 : return ret;
105 :
106 4 : ret = -ESRCH;
107 4 : rcu_read_lock();
108 4 : switch (which) {
109 4 : case IOPRIO_WHO_PROCESS:
110 4 : if (!who)
111 4 : p = current;
112 : else
113 0 : p = find_task_by_vpid(who);
114 4 : if (p)
115 4 : ret = set_task_ioprio(p, ioprio);
116 : break;
117 0 : case IOPRIO_WHO_PGRP:
118 0 : if (!who)
119 0 : pgrp = task_pgrp(current);
120 : else
121 0 : pgrp = find_vpid(who);
122 0 : do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
123 0 : ret = set_task_ioprio(p, ioprio);
124 0 : if (ret)
125 : break;
126 0 : } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
127 : break;
128 0 : case IOPRIO_WHO_USER:
129 0 : uid = make_kuid(current_user_ns(), who);
130 0 : if (!uid_valid(uid))
131 : break;
132 0 : if (!who)
133 0 : user = current_user();
134 : else
135 0 : user = find_user(uid);
136 :
137 0 : if (!user)
138 : break;
139 :
140 0 : for_each_process_thread(g, p) {
141 0 : if (!uid_eq(task_uid(p), uid) ||
142 0 : !task_pid_vnr(p))
143 0 : continue;
144 0 : ret = set_task_ioprio(p, ioprio);
145 0 : if (ret)
146 0 : goto free_uid;
147 : }
148 0 : free_uid:
149 0 : if (who)
150 0 : free_uid(user);
151 : break;
152 : default:
153 : ret = -EINVAL;
154 : }
155 :
156 4 : rcu_read_unlock();
157 4 : return ret;
158 : }
159 :
160 2 : static int get_task_ioprio(struct task_struct *p)
161 : {
162 2 : int ret;
163 :
164 2 : ret = security_task_getioprio(p);
165 2 : if (ret)
166 0 : goto out;
167 2 : ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
168 2 : task_lock(p);
169 2 : if (p->io_context)
170 2 : ret = p->io_context->ioprio;
171 2 : task_unlock(p);
172 2 : out:
173 2 : return ret;
174 : }
175 :
176 0 : int ioprio_best(unsigned short aprio, unsigned short bprio)
177 : {
178 0 : if (!ioprio_valid(aprio))
179 0 : aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
180 0 : if (!ioprio_valid(bprio))
181 0 : bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
182 :
183 0 : return min(aprio, bprio);
184 : }
185 :
186 4 : SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
187 : {
188 2 : struct task_struct *g, *p;
189 2 : struct user_struct *user;
190 2 : struct pid *pgrp;
191 2 : kuid_t uid;
192 2 : int ret = -ESRCH;
193 2 : int tmpio;
194 :
195 2 : rcu_read_lock();
196 2 : switch (which) {
197 2 : case IOPRIO_WHO_PROCESS:
198 2 : if (!who)
199 2 : p = current;
200 : else
201 0 : p = find_task_by_vpid(who);
202 2 : if (p)
203 2 : ret = get_task_ioprio(p);
204 : break;
205 0 : case IOPRIO_WHO_PGRP:
206 0 : if (!who)
207 0 : pgrp = task_pgrp(current);
208 : else
209 0 : pgrp = find_vpid(who);
210 0 : do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
211 0 : tmpio = get_task_ioprio(p);
212 0 : if (tmpio < 0)
213 0 : continue;
214 0 : if (ret == -ESRCH)
215 : ret = tmpio;
216 : else
217 0 : ret = ioprio_best(ret, tmpio);
218 0 : } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
219 : break;
220 0 : case IOPRIO_WHO_USER:
221 0 : uid = make_kuid(current_user_ns(), who);
222 0 : if (!who)
223 0 : user = current_user();
224 : else
225 0 : user = find_user(uid);
226 :
227 0 : if (!user)
228 : break;
229 :
230 0 : for_each_process_thread(g, p) {
231 0 : if (!uid_eq(task_uid(p), user->uid) ||
232 0 : !task_pid_vnr(p))
233 0 : continue;
234 0 : tmpio = get_task_ioprio(p);
235 0 : if (tmpio < 0)
236 0 : continue;
237 0 : if (ret == -ESRCH)
238 : ret = tmpio;
239 : else
240 0 : ret = ioprio_best(ret, tmpio);
241 : }
242 :
243 0 : if (who)
244 0 : free_uid(user);
245 : break;
246 : default:
247 : ret = -EINVAL;
248 : }
249 :
250 2 : rcu_read_unlock();
251 2 : return ret;
252 : }
|
