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![Eric W. Biederman](/assets/img/avatar_default.png)
There isn't any real advantage to this change except that it allows the old functions to be removed. Which is easier on maintenance and puts the code in a more uniform style. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
233 lines
4.7 KiB
C
233 lines
4.7 KiB
C
/*
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* fs/ioprio.c
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*
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* Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
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*
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* Helper functions for setting/querying io priorities of processes. The
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* system calls closely mimmick getpriority/setpriority, see the man page for
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* those. The prio argument is a composite of prio class and prio data, where
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* the data argument has meaning within that class. The standard scheduling
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* classes have 8 distinct prio levels, with 0 being the highest prio and 7
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* being the lowest.
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*
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* IOW, setting BE scheduling class with prio 2 is done ala:
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*
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* unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
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*
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* ioprio_set(PRIO_PROCESS, pid, prio);
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*
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* See also Documentation/block/ioprio.txt
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*
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*/
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#include <linux/kernel.h>
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#include <linux/ioprio.h>
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#include <linux/blkdev.h>
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#include <linux/capability.h>
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#include <linux/syscalls.h>
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#include <linux/security.h>
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static int set_task_ioprio(struct task_struct *task, int ioprio)
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{
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int err;
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struct io_context *ioc;
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if (task->uid != current->euid &&
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task->uid != current->uid && !capable(CAP_SYS_NICE))
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return -EPERM;
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err = security_task_setioprio(task, ioprio);
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if (err)
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return err;
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task_lock(task);
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task->ioprio = ioprio;
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ioc = task->io_context;
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/* see wmb() in current_io_context() */
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smp_read_barrier_depends();
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if (ioc)
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ioc->ioprio_changed = 1;
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task_unlock(task);
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return 0;
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}
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asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
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{
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int class = IOPRIO_PRIO_CLASS(ioprio);
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int data = IOPRIO_PRIO_DATA(ioprio);
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struct task_struct *p, *g;
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struct user_struct *user;
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struct pid *pgrp;
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int ret;
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switch (class) {
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case IOPRIO_CLASS_RT:
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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/* fall through, rt has prio field too */
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case IOPRIO_CLASS_BE:
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if (data >= IOPRIO_BE_NR || data < 0)
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return -EINVAL;
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break;
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case IOPRIO_CLASS_IDLE:
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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break;
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default:
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return -EINVAL;
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}
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ret = -ESRCH;
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/*
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* We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
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* so we can't use rcu_read_lock(). See re-copy of ->ioprio
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* in copy_process().
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*/
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read_lock(&tasklist_lock);
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switch (which) {
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case IOPRIO_WHO_PROCESS:
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if (!who)
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p = current;
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else
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p = find_task_by_pid(who);
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if (p)
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ret = set_task_ioprio(p, ioprio);
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break;
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case IOPRIO_WHO_PGRP:
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if (!who)
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pgrp = task_pgrp(current);
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else
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pgrp = find_pid(who);
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do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
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ret = set_task_ioprio(p, ioprio);
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if (ret)
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break;
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} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
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break;
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case IOPRIO_WHO_USER:
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if (!who)
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user = current->user;
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else
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user = find_user(who);
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if (!user)
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break;
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do_each_thread(g, p) {
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if (p->uid != who)
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continue;
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ret = set_task_ioprio(p, ioprio);
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if (ret)
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goto free_uid;
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} while_each_thread(g, p);
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free_uid:
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if (who)
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free_uid(user);
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break;
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default:
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ret = -EINVAL;
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}
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read_unlock(&tasklist_lock);
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return ret;
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}
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static int get_task_ioprio(struct task_struct *p)
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{
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int ret;
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ret = security_task_getioprio(p);
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if (ret)
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goto out;
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ret = p->ioprio;
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out:
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return ret;
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}
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int ioprio_best(unsigned short aprio, unsigned short bprio)
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{
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unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
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unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
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if (aclass == IOPRIO_CLASS_NONE)
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aclass = IOPRIO_CLASS_BE;
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if (bclass == IOPRIO_CLASS_NONE)
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bclass = IOPRIO_CLASS_BE;
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if (aclass == bclass)
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return min(aprio, bprio);
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if (aclass > bclass)
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return bprio;
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else
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return aprio;
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}
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asmlinkage long sys_ioprio_get(int which, int who)
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{
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struct task_struct *g, *p;
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struct user_struct *user;
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struct pid *pgrp;
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int ret = -ESRCH;
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int tmpio;
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read_lock(&tasklist_lock);
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switch (which) {
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case IOPRIO_WHO_PROCESS:
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if (!who)
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p = current;
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else
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p = find_task_by_pid(who);
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if (p)
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ret = get_task_ioprio(p);
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break;
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case IOPRIO_WHO_PGRP:
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if (!who)
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pgrp = task_pgrp(current);
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else
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pgrp = find_pid(who);
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do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
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tmpio = get_task_ioprio(p);
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if (tmpio < 0)
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continue;
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if (ret == -ESRCH)
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ret = tmpio;
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else
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ret = ioprio_best(ret, tmpio);
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} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
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break;
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case IOPRIO_WHO_USER:
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if (!who)
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user = current->user;
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else
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user = find_user(who);
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if (!user)
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break;
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do_each_thread(g, p) {
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if (p->uid != user->uid)
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continue;
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tmpio = get_task_ioprio(p);
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if (tmpio < 0)
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continue;
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if (ret == -ESRCH)
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ret = tmpio;
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else
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ret = ioprio_best(ret, tmpio);
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} while_each_thread(g, p);
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if (who)
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free_uid(user);
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break;
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default:
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ret = -EINVAL;
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}
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read_unlock(&tasklist_lock);
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return ret;
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}
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