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>
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();
51 if (ioc && ioc->set_ioprio)
52 ioc->set_ioprio(ioc, ioprio);
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))
85 read_lock_irq(&tasklist_lock);
87 case IOPRIO_WHO_PROCESS:
91 p = find_task_by_pid(who);
93 ret = set_task_ioprio(p, ioprio);
97 who = process_group(current);
98 do_each_task_pid(who, PIDTYPE_PGID, p) {
99 ret = set_task_ioprio(p, ioprio);
102 } while_each_task_pid(who, PIDTYPE_PGID, p);
104 case IOPRIO_WHO_USER:
106 user = current->user;
108 user = find_user(vx_current_xid(), who);
113 do_each_thread(g, p) {
116 ret = set_task_ioprio(p, ioprio);
119 } while_each_thread(g, p);
128 read_unlock_irq(&tasklist_lock);
132 static int get_task_ioprio(struct task_struct *p)
136 ret = security_task_getioprio(p);
144 int ioprio_best(unsigned short aprio, unsigned short bprio)
146 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
147 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
149 if (!ioprio_valid(aprio))
151 if (!ioprio_valid(bprio))
154 if (aclass == IOPRIO_CLASS_NONE)
155 aclass = IOPRIO_CLASS_BE;
156 if (bclass == IOPRIO_CLASS_NONE)
157 bclass = IOPRIO_CLASS_BE;
159 if (aclass == bclass)
160 return min(aprio, bprio);
167 asmlinkage long sys_ioprio_get(int which, int who)
169 struct task_struct *g, *p;
170 struct user_struct *user;
174 read_lock_irq(&tasklist_lock);
176 case IOPRIO_WHO_PROCESS:
180 p = find_task_by_pid(who);
182 ret = get_task_ioprio(p);
184 case IOPRIO_WHO_PGRP:
186 who = process_group(current);
187 do_each_task_pid(who, PIDTYPE_PGID, p) {
188 tmpio = get_task_ioprio(p);
194 ret = ioprio_best(ret, tmpio);
195 } while_each_task_pid(who, PIDTYPE_PGID, p);
197 case IOPRIO_WHO_USER:
199 user = current->user;
201 user = find_user(vx_current_xid(), who);
206 do_each_thread(g, p) {
207 if (p->uid != user->uid)
209 tmpio = get_task_ioprio(p);
215 ret = ioprio_best(ret, tmpio);
216 } while_each_thread(g, p);
225 read_unlock_irq(&tasklist_lock);