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![Jens Axboe](/assets/img/avatar_default.png)
Currently you must be root to set idle io prio class on a process. This is due to the fact that the idle class is implemented as a true idle class, meaning that it will not make progress if someone else is requesting disk access. Unfortunately this means that it opens DOS opportunities by locking down file system resources, hence it is root only at the moment. This patch relaxes the idle class a little, by removing the truly idle part (which entals a grace period with associated timer). The modifications make the idle class as close to zero impact as can be done while still guarenteeing progress. This means we can relax the root only criteria as well. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
248 lines
5 KiB
C
248 lines
5 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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#include <linux/pid_namespace.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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do {
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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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break;
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ioc = alloc_io_context(GFP_ATOMIC, -1);
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if (!ioc) {
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err = -ENOMEM;
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break;
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}
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task->io_context = ioc;
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} while (1);
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if (!err) {
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ioc->ioprio = ioprio;
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ioc->ioprio_changed = 1;
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}
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task_unlock(task);
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return err;
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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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break;
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case IOPRIO_CLASS_NONE:
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if (data)
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return -EINVAL;
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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_vpid(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_vpid(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 = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
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if (p->io_context)
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ret = p->io_context->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_vpid(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_vpid(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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