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-rw-r--r--block/ioprio.c241
1 files changed, 241 insertions, 0 deletions
diff --git a/block/ioprio.c b/block/ioprio.c
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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/blkdev.h>
27#include <linux/capability.h>
28#include <linux/syscalls.h>
29#include <linux/security.h>
30#include <linux/pid_namespace.h>
31
32int set_task_ioprio(struct task_struct *task, int ioprio)
33{
34 int err;
35 struct io_context *ioc;
36 const struct cred *cred = current_cred(), *tcred;
37
38 rcu_read_lock();
39 tcred = __task_cred(task);
40 if (!uid_eq(tcred->uid, cred->euid) &&
41 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
42 rcu_read_unlock();
43 return -EPERM;
44 }
45 rcu_read_unlock();
46
47 err = security_task_setioprio(task, ioprio);
48 if (err)
49 return err;
50
51 ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
52 if (ioc) {
53 ioc->ioprio = ioprio;
54 put_io_context(ioc);
55 }
56
57 return err;
58}
59EXPORT_SYMBOL_GPL(set_task_ioprio);
60
61SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
62{
63 int class = IOPRIO_PRIO_CLASS(ioprio);
64 int data = IOPRIO_PRIO_DATA(ioprio);
65 struct task_struct *p, *g;
66 struct user_struct *user;
67 struct pid *pgrp;
68 kuid_t uid;
69 int ret;
70
71 switch (class) {
72 case IOPRIO_CLASS_RT:
73 if (!capable(CAP_SYS_ADMIN))
74 return -EPERM;
75 /* fall through, rt has prio field too */
76 case IOPRIO_CLASS_BE:
77 if (data >= IOPRIO_BE_NR || data < 0)
78 return -EINVAL;
79
80 break;
81 case IOPRIO_CLASS_IDLE:
82 break;
83 case IOPRIO_CLASS_NONE:
84 if (data)
85 return -EINVAL;
86 break;
87 default:
88 return -EINVAL;
89 }
90
91 ret = -ESRCH;
92 rcu_read_lock();
93 switch (which) {
94 case IOPRIO_WHO_PROCESS:
95 if (!who)
96 p = current;
97 else
98 p = find_task_by_vpid(who);
99 if (p)
100 ret = set_task_ioprio(p, ioprio);
101 break;
102 case IOPRIO_WHO_PGRP:
103 if (!who)
104 pgrp = task_pgrp(current);
105 else
106 pgrp = find_vpid(who);
107 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
108 ret = set_task_ioprio(p, ioprio);
109 if (ret)
110 break;
111 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
112 break;
113 case IOPRIO_WHO_USER:
114 uid = make_kuid(current_user_ns(), who);
115 if (!uid_valid(uid))
116 break;
117 if (!who)
118 user = current_user();
119 else
120 user = find_user(uid);
121
122 if (!user)
123 break;
124
125 do_each_thread(g, p) {
126 if (!uid_eq(task_uid(p), uid))
127 continue;
128 ret = set_task_ioprio(p, ioprio);
129 if (ret)
130 goto free_uid;
131 } while_each_thread(g, p);
132free_uid:
133 if (who)
134 free_uid(user);
135 break;
136 default:
137 ret = -EINVAL;
138 }
139
140 rcu_read_unlock();
141 return ret;
142}
143
144static int get_task_ioprio(struct task_struct *p)
145{
146 int ret;
147
148 ret = security_task_getioprio(p);
149 if (ret)
150 goto out;
151 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
152 if (p->io_context)
153 ret = p->io_context->ioprio;
154out:
155 return ret;
156}
157
158int ioprio_best(unsigned short aprio, unsigned short bprio)
159{
160 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
161 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
162
163 if (aclass == IOPRIO_CLASS_NONE)
164 aclass = IOPRIO_CLASS_BE;
165 if (bclass == IOPRIO_CLASS_NONE)
166 bclass = IOPRIO_CLASS_BE;
167
168 if (aclass == bclass)
169 return min(aprio, bprio);
170 if (aclass > bclass)
171 return bprio;
172 else
173 return aprio;
174}
175
176SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
177{
178 struct task_struct *g, *p;
179 struct user_struct *user;
180 struct pid *pgrp;
181 kuid_t uid;
182 int ret = -ESRCH;
183 int tmpio;
184
185 rcu_read_lock();
186 switch (which) {
187 case IOPRIO_WHO_PROCESS:
188 if (!who)
189 p = current;
190 else
191 p = find_task_by_vpid(who);
192 if (p)
193 ret = get_task_ioprio(p);
194 break;
195 case IOPRIO_WHO_PGRP:
196 if (!who)
197 pgrp = task_pgrp(current);
198 else
199 pgrp = find_vpid(who);
200 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
201 tmpio = get_task_ioprio(p);
202 if (tmpio < 0)
203 continue;
204 if (ret == -ESRCH)
205 ret = tmpio;
206 else
207 ret = ioprio_best(ret, tmpio);
208 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
209 break;
210 case IOPRIO_WHO_USER:
211 uid = make_kuid(current_user_ns(), who);
212 if (!who)
213 user = current_user();
214 else
215 user = find_user(uid);
216
217 if (!user)
218 break;
219
220 do_each_thread(g, p) {
221 if (!uid_eq(task_uid(p), user->uid))
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 } while_each_thread(g, p);
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}
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