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Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
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/kernel.h>
23#include <linux/ioprio.h>
24#include <linux/blkdev.h>
25#include <linux/capability.h>
26#include <linux/syscalls.h>
27#include <linux/security.h>
28
29static int set_task_ioprio(struct task_struct *task, int ioprio)
30{
31 int err;
32 struct io_context *ioc;
33
34 if (task->uid != current->euid &&
35 task->uid != current->uid && !capable(CAP_SYS_NICE))
36 return -EPERM;
37
38 err = security_task_setioprio(task, ioprio);
39 if (err)
40 return err;
41
42 task_lock(task);
43
44 task->ioprio = ioprio;
45
46 ioc = task->io_context;
47 /* see wmb() in current_io_context() */
48 smp_read_barrier_depends();
49
50 if (ioc)
51 ioc->ioprio_changed = 1;
52
53 task_unlock(task);
54 return 0;
55}
56
57asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
58{
59 int class = IOPRIO_PRIO_CLASS(ioprio);
60 int data = IOPRIO_PRIO_DATA(ioprio);
61 struct task_struct *p, *g;
62 struct user_struct *user;
63 int ret;
64
65 switch (class) {
66 case IOPRIO_CLASS_RT:
67 if (!capable(CAP_SYS_ADMIN))
68 return -EPERM;
69 /* fall through, rt has prio field too */
70 case IOPRIO_CLASS_BE:
71 if (data >= IOPRIO_BE_NR || data < 0)
72 return -EINVAL;
73
74 break;
75 case IOPRIO_CLASS_IDLE:
76 if (!capable(CAP_SYS_ADMIN))
77 return -EPERM;
78 break;
79 default:
80 return -EINVAL;
81 }
82
83 ret = -ESRCH;
84 /*
85 * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
86 * so we can't use rcu_read_lock(). See re-copy of ->ioprio
87 * in copy_process().
88 */
89 read_lock(&tasklist_lock);
90 switch (which) {
91 case IOPRIO_WHO_PROCESS:
92 if (!who)
93 p = current;
94 else
95 p = find_task_by_pid(who);
96 if (p)
97 ret = set_task_ioprio(p, ioprio);
98 break;
99 case IOPRIO_WHO_PGRP:
100 if (!who)
101 who = process_group(current);
102 do_each_task_pid(who, PIDTYPE_PGID, p) {
103 ret = set_task_ioprio(p, ioprio);
104 if (ret)
105 break;
106 } while_each_task_pid(who, PIDTYPE_PGID, p);
107 break;
108 case IOPRIO_WHO_USER:
109 if (!who)
110 user = current->user;
111 else
112 user = find_user(who);
113
114 if (!user)
115 break;
116
117 do_each_thread(g, p) {
118 if (p->uid != who)
119 continue;
120 ret = set_task_ioprio(p, ioprio);
121 if (ret)
122 goto free_uid;
123 } while_each_thread(g, p);
124free_uid:
125 if (who)
126 free_uid(user);
127 break;
128 default:
129 ret = -EINVAL;
130 }
131
132 read_unlock(&tasklist_lock);
133 return ret;
134}
135
136static int get_task_ioprio(struct task_struct *p)
137{
138 int ret;
139
140 ret = security_task_getioprio(p);
141 if (ret)
142 goto out;
143 ret = p->ioprio;
144out:
145 return ret;
146}
147
148int ioprio_best(unsigned short aprio, unsigned short bprio)
149{
150 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
151 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
152
153 if (aclass == IOPRIO_CLASS_NONE)
154 aclass = IOPRIO_CLASS_BE;
155 if (bclass == IOPRIO_CLASS_NONE)
156 bclass = IOPRIO_CLASS_BE;
157
158 if (aclass == bclass)
159 return min(aprio, bprio);
160 if (aclass > bclass)
161 return bprio;
162 else
163 return aprio;
164}
165
166asmlinkage long sys_ioprio_get(int which, int who)
167{
168 struct task_struct *g, *p;
169 struct user_struct *user;
170 int ret = -ESRCH;
171 int tmpio;
172
173 read_lock(&tasklist_lock);
174 switch (which) {
175 case IOPRIO_WHO_PROCESS:
176 if (!who)
177 p = current;
178 else
179 p = find_task_by_pid(who);
180 if (p)
181 ret = get_task_ioprio(p);
182 break;
183 case IOPRIO_WHO_PGRP:
184 if (!who)
185 who = process_group(current);
186 do_each_task_pid(who, PIDTYPE_PGID, p) {
187 tmpio = get_task_ioprio(p);
188 if (tmpio < 0)
189 continue;
190 if (ret == -ESRCH)
191 ret = tmpio;
192 else
193 ret = ioprio_best(ret, tmpio);
194 } while_each_task_pid(who, PIDTYPE_PGID, p);
195 break;
196 case IOPRIO_WHO_USER:
197 if (!who)
198 user = current->user;
199 else
200 user = find_user(who);
201
202 if (!user)
203 break;
204
205 do_each_thread(g, p) {
206 if (p->uid != user->uid)
207 continue;
208 tmpio = get_task_ioprio(p);
209 if (tmpio < 0)
210 continue;
211 if (ret == -ESRCH)
212 ret = tmpio;
213 else
214 ret = ioprio_best(ret, tmpio);
215 } while_each_thread(g, p);
216
217 if (who)
218 free_uid(user);
219 break;
220 default:
221 ret = -EINVAL;
222 }
223
224 read_unlock(&tasklist_lock);
225 return ret;
226}
227