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 for_each_process_thread(g, p) {
126 if (!uid_eq(task_uid(p), uid) ||
129 ret = set_task_ioprio(p, ioprio);
145 static int get_task_ioprio(struct task_struct *p)
149 ret = security_task_getioprio(p);
152 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
155 ret = p->io_context->ioprio;
161 int ioprio_best(unsigned short aprio, unsigned short bprio)
163 unsigned short aclass;
164 unsigned short bclass;
166 if (!ioprio_valid(aprio))
167 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
168 if (!ioprio_valid(bprio))
169 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
171 aclass = IOPRIO_PRIO_CLASS(aprio);
172 bclass = IOPRIO_PRIO_CLASS(bprio);
173 if (aclass == bclass)
174 return min(aprio, bprio);
181 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
183 struct task_struct *g, *p;
184 struct user_struct *user;
192 case IOPRIO_WHO_PROCESS:
196 p = find_task_by_vpid(who);
198 ret = get_task_ioprio(p);
200 case IOPRIO_WHO_PGRP:
202 pgrp = task_pgrp(current);
204 pgrp = find_vpid(who);
205 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
206 tmpio = get_task_ioprio(p);
212 ret = ioprio_best(ret, tmpio);
213 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
215 case IOPRIO_WHO_USER:
216 uid = make_kuid(current_user_ns(), who);
218 user = current_user();
220 user = find_user(uid);
225 for_each_process_thread(g, p) {
226 if (!uid_eq(task_uid(p), user->uid) ||
229 tmpio = get_task_ioprio(p);
235 ret = ioprio_best(ret, tmpio);