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git.proxmox.com Git - mirror_ubuntu-zesty-kernel.git/blob - fs/ioprio.c
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>
28 #include <linux/pid_namespace.h>
30 static int set_task_ioprio(struct task_struct
*task
, int ioprio
)
33 struct io_context
*ioc
;
35 if (task
->uid
!= current
->euid
&&
36 task
->uid
!= current
->uid
&& !capable(CAP_SYS_NICE
))
39 err
= security_task_setioprio(task
, ioprio
);
45 task
->ioprio
= ioprio
;
47 ioc
= task
->io_context
;
48 /* see wmb() in current_io_context() */
49 smp_read_barrier_depends();
52 ioc
->ioprio_changed
= 1;
58 asmlinkage
long sys_ioprio_set(int which
, int who
, int ioprio
)
60 int class = IOPRIO_PRIO_CLASS(ioprio
);
61 int data
= IOPRIO_PRIO_DATA(ioprio
);
62 struct task_struct
*p
, *g
;
63 struct user_struct
*user
;
69 if (!capable(CAP_SYS_ADMIN
))
71 /* fall through, rt has prio field too */
73 if (data
>= IOPRIO_BE_NR
|| data
< 0)
77 case IOPRIO_CLASS_IDLE
:
78 if (!capable(CAP_SYS_ADMIN
))
87 * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
88 * so we can't use rcu_read_lock(). See re-copy of ->ioprio
91 read_lock(&tasklist_lock
);
93 case IOPRIO_WHO_PROCESS
:
97 p
= find_task_by_pid_ns(who
,
98 current
->nsproxy
->pid_ns
);
100 ret
= set_task_ioprio(p
, ioprio
);
102 case IOPRIO_WHO_PGRP
:
104 pgrp
= task_pgrp(current
);
106 pgrp
= find_vpid(who
);
107 do_each_pid_task(pgrp
, PIDTYPE_PGID
, p
) {
108 ret
= set_task_ioprio(p
, ioprio
);
111 } while_each_pid_task(pgrp
, PIDTYPE_PGID
, p
);
113 case IOPRIO_WHO_USER
:
115 user
= current
->user
;
117 user
= find_user(who
);
122 do_each_thread(g
, p
) {
125 ret
= set_task_ioprio(p
, ioprio
);
128 } while_each_thread(g
, p
);
137 read_unlock(&tasklist_lock
);
141 static int get_task_ioprio(struct task_struct
*p
)
145 ret
= security_task_getioprio(p
);
153 int ioprio_best(unsigned short aprio
, unsigned short bprio
)
155 unsigned short aclass
= IOPRIO_PRIO_CLASS(aprio
);
156 unsigned short bclass
= IOPRIO_PRIO_CLASS(bprio
);
158 if (aclass
== IOPRIO_CLASS_NONE
)
159 aclass
= IOPRIO_CLASS_BE
;
160 if (bclass
== IOPRIO_CLASS_NONE
)
161 bclass
= IOPRIO_CLASS_BE
;
163 if (aclass
== bclass
)
164 return min(aprio
, bprio
);
171 asmlinkage
long sys_ioprio_get(int which
, int who
)
173 struct task_struct
*g
, *p
;
174 struct user_struct
*user
;
179 read_lock(&tasklist_lock
);
181 case IOPRIO_WHO_PROCESS
:
185 p
= find_task_by_pid_ns(who
,
186 current
->nsproxy
->pid_ns
);
188 ret
= get_task_ioprio(p
);
190 case IOPRIO_WHO_PGRP
:
192 pgrp
= task_pgrp(current
);
194 pgrp
= find_vpid(who
);
195 do_each_pid_task(pgrp
, PIDTYPE_PGID
, p
) {
196 tmpio
= get_task_ioprio(p
);
202 ret
= ioprio_best(ret
, tmpio
);
203 } while_each_pid_task(pgrp
, PIDTYPE_PGID
, p
);
205 case IOPRIO_WHO_USER
:
207 user
= current
->user
;
209 user
= find_user(who
);
214 do_each_thread(g
, p
) {
215 if (p
->uid
!= user
->uid
)
217 tmpio
= get_task_ioprio(p
);
223 ret
= ioprio_best(ret
, tmpio
);
224 } while_each_thread(g
, p
);
233 read_unlock(&tasklist_lock
);