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 (tcred->uid != cred->euid &&
41 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);
54 ioc->ioprio_changed = 1;
60 EXPORT_SYMBOL_GPL(set_task_ioprio);
62 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
64 int class = IOPRIO_PRIO_CLASS(ioprio);
65 int data = IOPRIO_PRIO_DATA(ioprio);
66 struct task_struct *p, *g;
67 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:
115 user = current_user();
117 user = find_user(who);
122 do_each_thread(g, p) {
123 if (__task_cred(p)->uid != who)
125 ret = set_task_ioprio(p, ioprio);
128 } while_each_thread(g, p);
141 static int get_task_ioprio(struct task_struct *p)
145 ret = security_task_getioprio(p);
148 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
150 ret = p->io_context->ioprio;
155 int ioprio_best(unsigned short aprio, unsigned short bprio)
157 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
158 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
160 if (aclass == IOPRIO_CLASS_NONE)
161 aclass = IOPRIO_CLASS_BE;
162 if (bclass == IOPRIO_CLASS_NONE)
163 bclass = IOPRIO_CLASS_BE;
165 if (aclass == bclass)
166 return min(aprio, bprio);
173 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
175 struct task_struct *g, *p;
176 struct user_struct *user;
183 case IOPRIO_WHO_PROCESS:
187 p = find_task_by_vpid(who);
189 ret = get_task_ioprio(p);
191 case IOPRIO_WHO_PGRP:
193 pgrp = task_pgrp(current);
195 pgrp = find_vpid(who);
196 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
197 tmpio = get_task_ioprio(p);
203 ret = ioprio_best(ret, tmpio);
204 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
206 case IOPRIO_WHO_USER:
208 user = current_user();
210 user = find_user(who);
215 do_each_thread(g, p) {
216 if (__task_cred(p)->uid != user->uid)
218 tmpio = get_task_ioprio(p);
224 ret = ioprio_best(ret, tmpio);
225 } while_each_thread(g, p);