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/vs_base.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;
68 if (!capable(CAP_SYS_ADMIN))
70 /* fall through, rt has prio field too */
72 if (data >= IOPRIO_BE_NR || data < 0)
76 case IOPRIO_CLASS_IDLE:
77 if (!capable(CAP_SYS_ADMIN))
86 * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
87 * so we can't use rcu_read_lock(). See re-copy of ->ioprio
90 read_lock(&tasklist_lock);
92 case IOPRIO_WHO_PROCESS:
96 p = find_task_by_pid(who);
98 ret = set_task_ioprio(p, ioprio);
100 case IOPRIO_WHO_PGRP:
102 who = process_group(current);
103 do_each_task_pid(who, PIDTYPE_PGID, p) {
104 if (!vx_check(p->xid, VS_ADMIN_P | VS_IDENT))
106 ret = set_task_ioprio(p, ioprio);
109 } while_each_task_pid(who, PIDTYPE_PGID, p);
111 case IOPRIO_WHO_USER:
113 user = current->user;
115 user = find_user(vx_current_xid(), who);
120 do_each_thread(g, p) {
123 ret = set_task_ioprio(p, ioprio);
126 } while_each_thread(g, p);
135 read_unlock(&tasklist_lock);
139 static int get_task_ioprio(struct task_struct *p)
143 ret = security_task_getioprio(p);
151 int ioprio_best(unsigned short aprio, unsigned short bprio)
153 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
154 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
156 if (aclass == IOPRIO_CLASS_NONE)
157 aclass = IOPRIO_CLASS_BE;
158 if (bclass == IOPRIO_CLASS_NONE)
159 bclass = IOPRIO_CLASS_BE;
161 if (aclass == bclass)
162 return min(aprio, bprio);
169 asmlinkage long sys_ioprio_get(int which, int who)
171 struct task_struct *g, *p;
172 struct user_struct *user;
176 read_lock(&tasklist_lock);
178 case IOPRIO_WHO_PROCESS:
182 p = find_task_by_pid(who);
184 ret = get_task_ioprio(p);
186 case IOPRIO_WHO_PGRP:
188 who = process_group(current);
189 do_each_task_pid(who, PIDTYPE_PGID, p) {
190 if (!vx_check(p->xid, VS_ADMIN_P | VS_IDENT))
192 tmpio = get_task_ioprio(p);
198 ret = ioprio_best(ret, tmpio);
199 } while_each_task_pid(who, PIDTYPE_PGID, p);
201 case IOPRIO_WHO_USER:
203 user = current->user;
205 user = find_user(vx_current_xid(), who);
210 do_each_thread(g, p) {
211 if (p->uid != user->uid)
213 tmpio = get_task_ioprio(p);
219 ret = ioprio_best(ret, tmpio);
220 } while_each_thread(g, p);
229 read_unlock(&tasklist_lock);