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/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>
32 int set_task_ioprio(struct task_struct
*task
, int ioprio
)
35 struct io_context
*ioc
;
36 const struct cred
*cred
= current_cred(), *tcred
;
39 tcred
= __task_cred(task
);
40 if (!uid_eq(tcred
->uid
, cred
->euid
) &&
41 !uid_eq(tcred
->uid
, cred
->uid
) && !capable(CAP_SYS_NICE
)) {
47 err
= security_task_setioprio(task
, ioprio
);
51 ioc
= get_task_io_context(task
, GFP_ATOMIC
, NUMA_NO_NODE
);
59 EXPORT_SYMBOL_GPL(set_task_ioprio
);
61 SYSCALL_DEFINE3(ioprio_set
, int, which
, int, who
, int, ioprio
)
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
;
73 if (!capable(CAP_SYS_ADMIN
))
75 /* fall through, rt has prio field too */
77 if (data
>= IOPRIO_BE_NR
|| data
< 0)
81 case IOPRIO_CLASS_IDLE
:
83 case IOPRIO_CLASS_NONE
:
94 case IOPRIO_WHO_PROCESS
:
98 p
= find_task_by_vpid(who
);
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_thread(pgrp
, PIDTYPE_PGID
, p
) {
108 ret
= set_task_ioprio(p
, ioprio
);
111 } while_each_pid_thread(pgrp
, PIDTYPE_PGID
, p
);
113 case IOPRIO_WHO_USER
:
114 uid
= make_kuid(current_user_ns(), who
);
118 user
= current_user();
120 user
= find_user(uid
);
125 do_each_thread(g
, p
) {
126 if (!uid_eq(task_uid(p
), uid
))
128 ret
= set_task_ioprio(p
, ioprio
);
131 } while_each_thread(g
, p
);
144 static int get_task_ioprio(struct task_struct
*p
)
148 ret
= security_task_getioprio(p
);
151 ret
= IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE
, IOPRIO_NORM
);
154 ret
= p
->io_context
->ioprio
;
160 int ioprio_best(unsigned short aprio
, unsigned short bprio
)
162 unsigned short aclass
;
163 unsigned short bclass
;
165 if (!ioprio_valid(aprio
))
166 aprio
= IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE
, IOPRIO_NORM
);
167 if (!ioprio_valid(bprio
))
168 bprio
= IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE
, IOPRIO_NORM
);
170 aclass
= IOPRIO_PRIO_CLASS(aprio
);
171 bclass
= IOPRIO_PRIO_CLASS(bprio
);
172 if (aclass
== bclass
)
173 return min(aprio
, bprio
);
180 SYSCALL_DEFINE2(ioprio_get
, int, which
, int, who
)
182 struct task_struct
*g
, *p
;
183 struct user_struct
*user
;
191 case IOPRIO_WHO_PROCESS
:
195 p
= find_task_by_vpid(who
);
197 ret
= get_task_ioprio(p
);
199 case IOPRIO_WHO_PGRP
:
201 pgrp
= task_pgrp(current
);
203 pgrp
= find_vpid(who
);
204 do_each_pid_thread(pgrp
, PIDTYPE_PGID
, p
) {
205 tmpio
= get_task_ioprio(p
);
211 ret
= ioprio_best(ret
, tmpio
);
212 } while_each_pid_thread(pgrp
, PIDTYPE_PGID
, p
);
214 case IOPRIO_WHO_USER
:
215 uid
= make_kuid(current_user_ns(), who
);
217 user
= current_user();
219 user
= find_user(uid
);
224 do_each_thread(g
, p
) {
225 if (!uid_eq(task_uid(p
), user
->uid
))
227 tmpio
= get_task_ioprio(p
);
233 ret
= ioprio_best(ret
, tmpio
);
234 } while_each_thread(g
, p
);