4 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
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
13 * IOW, setting BE scheduling class with prio 2 is done ala:
15 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
17 * ioprio_set(PRIO_PROCESS, pid, prio);
19 * See also Documentation/block/ioprio.txt
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>
29 static int set_task_ioprio(struct task_struct
*task
, int ioprio
)
32 struct io_context
*ioc
;
34 if (task
->uid
!= current
->euid
&&
35 task
->uid
!= current
->uid
&& !capable(CAP_SYS_NICE
))
38 err
= security_task_setioprio(task
, ioprio
);
44 task
->ioprio
= ioprio
;
46 ioc
= task
->io_context
;
47 /* see wmb() in current_io_context() */
48 smp_read_barrier_depends();
51 ioc
->ioprio_changed
= 1;
57 asmlinkage
long sys_ioprio_set(int which
, int who
, int ioprio
)
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
;
68 if (!capable(CAP_SYS_ADMIN
))
70 /* fall through, rt has prio field too */
72 if (data
>= IOPRIO_BE_NR
|| data
< 0)
76 case IOPRIO_CLASS_IDLE
:
77 if (!capable(CAP_SYS_ADMIN
))
86 * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
87 * so we can't use rcu_read_lock(). See re-copy of ->ioprio
90 read_lock(&tasklist_lock
);
92 case IOPRIO_WHO_PROCESS
:
96 p
= find_task_by_pid(who
);
98 ret
= set_task_ioprio(p
, ioprio
);
100 case IOPRIO_WHO_PGRP
:
102 pgrp
= task_pgrp(current
);
104 pgrp
= find_pid(who
);
105 do_each_pid_task(pgrp
, PIDTYPE_PGID
, p
) {
106 ret
= set_task_ioprio(p
, ioprio
);
109 } while_each_pid_task(pgrp
, PIDTYPE_PGID
, p
);
111 case IOPRIO_WHO_USER
:
113 user
= current
->user
;
115 user
= find_user(who
);
120 do_each_thread(g
, p
) {
123 ret
= set_task_ioprio(p
, ioprio
);
126 } while_each_thread(g
, p
);
135 read_unlock(&tasklist_lock
);
139 static int get_task_ioprio(struct task_struct
*p
)
143 ret
= security_task_getioprio(p
);
151 int ioprio_best(unsigned short aprio
, unsigned short bprio
)
153 unsigned short aclass
= IOPRIO_PRIO_CLASS(aprio
);
154 unsigned short bclass
= IOPRIO_PRIO_CLASS(bprio
);
156 if (aclass
== IOPRIO_CLASS_NONE
)
157 aclass
= IOPRIO_CLASS_BE
;
158 if (bclass
== IOPRIO_CLASS_NONE
)
159 bclass
= IOPRIO_CLASS_BE
;
161 if (aclass
== bclass
)
162 return min(aprio
, bprio
);
169 asmlinkage
long sys_ioprio_get(int which
, int who
)
171 struct task_struct
*g
, *p
;
172 struct user_struct
*user
;
177 read_lock(&tasklist_lock
);
179 case IOPRIO_WHO_PROCESS
:
183 p
= find_task_by_pid(who
);
185 ret
= get_task_ioprio(p
);
187 case IOPRIO_WHO_PGRP
:
189 pgrp
= task_pgrp(current
);
191 pgrp
= find_pid(who
);
192 do_each_pid_task(pgrp
, PIDTYPE_PGID
, p
) {
193 tmpio
= get_task_ioprio(p
);
199 ret
= ioprio_best(ret
, tmpio
);
200 } while_each_pid_task(pgrp
, PIDTYPE_PGID
, p
);
202 case IOPRIO_WHO_USER
:
204 user
= current
->user
;
206 user
= find_user(who
);
211 do_each_thread(g
, p
) {
212 if (p
->uid
!= user
->uid
)
214 tmpio
= get_task_ioprio(p
);
220 ret
= ioprio_best(ret
, tmpio
);
221 } while_each_thread(g
, p
);
230 read_unlock(&tasklist_lock
);
This page took 0.034647 seconds and 5 git commands to generate.