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/ioprio.h>
25 #include <linux/blkdev.h>
26 #include <linux/capability.h>
27 #include <linux/syscalls.h>
28 #include <linux/security.h>
29 #include <linux/pid_namespace.h>
31 int set_task_ioprio(struct task_struct *task, int ioprio)
34 struct io_context *ioc;
35 const struct cred *cred = current_cred(), *tcred;
38 tcred = __task_cred(task);
39 if (tcred->uid != cred->euid &&
40 tcred->uid != cred->uid && !capable(CAP_SYS_NICE)) {
46 err = security_task_setioprio(task, ioprio);
52 ioc = task->io_context;
53 /* see wmb() in current_io_context() */
54 smp_read_barrier_depends();
58 ioc = alloc_io_context(GFP_ATOMIC, -1);
63 task->io_context = ioc;
68 ioc->ioprio_changed = 1;
74 EXPORT_SYMBOL_GPL(set_task_ioprio);
76 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
78 int class = IOPRIO_PRIO_CLASS(ioprio);
79 int data = IOPRIO_PRIO_DATA(ioprio);
80 struct task_struct *p, *g;
81 struct user_struct *user;
87 if (!capable(CAP_SYS_ADMIN))
89 /* fall through, rt has prio field too */
91 if (data >= IOPRIO_BE_NR || data < 0)
95 case IOPRIO_CLASS_IDLE:
97 case IOPRIO_CLASS_NONE:
107 * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
108 * so we can't use rcu_read_lock(). See re-copy of ->ioprio
111 read_lock(&tasklist_lock);
113 case IOPRIO_WHO_PROCESS:
117 p = find_task_by_vpid(who);
119 ret = set_task_ioprio(p, ioprio);
121 case IOPRIO_WHO_PGRP:
123 pgrp = task_pgrp(current);
125 pgrp = find_vpid(who);
126 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
127 ret = set_task_ioprio(p, ioprio);
130 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
132 case IOPRIO_WHO_USER:
134 user = current_user();
136 user = find_user(who);
141 do_each_thread(g, p) {
145 match = __task_cred(p)->uid == who;
149 ret = set_task_ioprio(p, ioprio);
152 } while_each_thread(g, p);
161 read_unlock(&tasklist_lock);
165 static int get_task_ioprio(struct task_struct *p)
169 ret = security_task_getioprio(p);
172 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
174 ret = p->io_context->ioprio;
179 int ioprio_best(unsigned short aprio, unsigned short bprio)
181 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
182 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
184 if (aclass == IOPRIO_CLASS_NONE)
185 aclass = IOPRIO_CLASS_BE;
186 if (bclass == IOPRIO_CLASS_NONE)
187 bclass = IOPRIO_CLASS_BE;
189 if (aclass == bclass)
190 return min(aprio, bprio);
197 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
199 struct task_struct *g, *p;
200 struct user_struct *user;
205 read_lock(&tasklist_lock);
207 case IOPRIO_WHO_PROCESS:
211 p = find_task_by_vpid(who);
213 ret = get_task_ioprio(p);
215 case IOPRIO_WHO_PGRP:
217 pgrp = task_pgrp(current);
219 pgrp = find_vpid(who);
220 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
221 tmpio = get_task_ioprio(p);
227 ret = ioprio_best(ret, tmpio);
228 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
230 case IOPRIO_WHO_USER:
232 user = current_user();
234 user = find_user(who);
239 do_each_thread(g, p) {
243 match = __task_cred(p)->uid == user->uid;
247 tmpio = get_task_ioprio(p);
253 ret = ioprio_best(ret, tmpio);
254 } while_each_thread(g, p);
263 read_unlock(&tasklist_lock);