4 * Copyright (C) 2004 Jens Axboe <axboe@suse.de>
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>
29 static int set_task_ioprio(struct task_struct *task, int ioprio)
32 struct io_context *ioc;
34 if (task->uid != current->euid &&
35 task->uid != current->uid && !capable(CAP_SYS_NICE))
38 err = security_task_setioprio(task, ioprio);
44 task->ioprio = ioprio;
46 ioc = task->io_context;
47 /* see wmb() in current_io_context() */
48 smp_read_barrier_depends();
50 if (ioc && ioc->set_ioprio)
51 ioc->set_ioprio(ioc, ioprio);
57 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
59 int class = IOPRIO_PRIO_CLASS(ioprio);
60 int data = IOPRIO_PRIO_DATA(ioprio);
61 struct task_struct *p, *g;
62 struct user_struct *user;
67 if (!capable(CAP_SYS_ADMIN))
69 /* fall through, rt has prio field too */
71 if (data >= IOPRIO_BE_NR || data < 0)
75 case IOPRIO_CLASS_IDLE:
76 if (!capable(CAP_SYS_ADMIN))
84 read_lock_irq(&tasklist_lock);
86 case IOPRIO_WHO_PROCESS:
90 p = find_task_by_pid(who);
92 ret = set_task_ioprio(p, ioprio);
96 who = process_group(current);
97 do_each_task_pid(who, PIDTYPE_PGID, p) {
98 ret = set_task_ioprio(p, ioprio);
101 } while_each_task_pid(who, PIDTYPE_PGID, p);
103 case IOPRIO_WHO_USER:
105 user = current->user;
107 user = find_user(who);
112 do_each_thread(g, p) {
115 ret = set_task_ioprio(p, ioprio);
118 } while_each_thread(g, p);
127 read_unlock_irq(&tasklist_lock);
131 static int get_task_ioprio(struct task_struct *p)
135 ret = security_task_getioprio(p);
143 asmlinkage long sys_ioprio_get(int which, int who)
145 struct task_struct *g, *p;
146 struct user_struct *user;
150 read_lock_irq(&tasklist_lock);
152 case IOPRIO_WHO_PROCESS:
156 p = find_task_by_pid(who);
158 ret = get_task_ioprio(p);
160 case IOPRIO_WHO_PGRP:
162 who = process_group(current);
163 do_each_task_pid(who, PIDTYPE_PGID, p) {
164 tmpio = get_task_ioprio(p);
170 ret = ioprio_best(ret, tmpio);
171 } while_each_task_pid(who, PIDTYPE_PGID, p);
173 case IOPRIO_WHO_USER:
175 user = current->user;
177 user = find_user(who);
182 do_each_thread(g, p) {
183 if (p->uid != user->uid)
185 tmpio = get_task_ioprio(p);
191 ret = ioprio_best(ret, tmpio);
192 } while_each_thread(g, p);
201 read_unlock_irq(&tasklist_lock);