LXR linux/fs/ioprio.c

   1/*
   2 * fs/ioprio.c
   3 *
   4 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
   5 *
   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
  11 * being the lowest.
  12 *
  13 * IOW, setting BE scheduling class with prio 2 is done ala:
  14 *
  15 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
  16 *
  17 * ioprio_set(PRIO_PROCESS, pid, prio);
  18 *
  19 * See also Documentation/block/ioprio.txt
  20 *
  21 */
  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/pid_namespace.h>
  29
  30static int set_task_ioprio(struct task_struct *task, int ioprio)
  31{
  32        int err;
  33        struct io_context *ioc;
  34
  35        if (task->uid != current->euid &&
  36            task->uid != current->uid && !capable(CAP_SYS_NICE))
  37                return -EPERM;
  38
  39        err = security_task_setioprio(task, ioprio);
  40        if (err)
  41                return err;
  42
  43        task_lock(task);
  44        do {
  45                ioc = task->io_context;
  46                /* see wmb() in current_io_context() */
  47                smp_read_barrier_depends();
  48                if (ioc)
  49                        break;
  50
  51                ioc = alloc_io_context(GFP_ATOMIC, -1);
  52                if (!ioc) {
  53                        err = -ENOMEM;
  54                        break;
  55                }
  56                task->io_context = ioc;
  57        } while (1);
  58
  59        if (!err) {
  60                ioc->ioprio = ioprio;
  61                ioc->ioprio_changed = 1;
  62        }
  63
  64        task_unlock(task);
  65        return err;
  66}
  67
  68asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
  69{
  70        int class = IOPRIO_PRIO_CLASS(ioprio);
  71        int data = IOPRIO_PRIO_DATA(ioprio);
  72        struct task_struct *p, *g;
  73        struct user_struct *user;
  74        struct pid *pgrp;
  75        int ret;
  76
  77        switch (class) {
  78                case IOPRIO_CLASS_RT:
  79                        if (!capable(CAP_SYS_ADMIN))
  80                                return -EPERM;
  81                        /* fall through, rt has prio field too */
  82                case IOPRIO_CLASS_BE:
  83                        if (data >= IOPRIO_BE_NR || data < 0)
  84                                return -EINVAL;
  85
  86                        break;
  87                case IOPRIO_CLASS_IDLE:
  88                        break;
  89                case IOPRIO_CLASS_NONE:
  90                        if (data)
  91                                return -EINVAL;
  92                        break;
  93                default:
  94                        return -EINVAL;
  95        }
  96
  97        ret = -ESRCH;
  98        /*
  99         * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
 100         * so we can't use rcu_read_lock(). See re-copy of ->ioprio
 101         * in copy_process().
 102         */
 103        read_lock(&tasklist_lock);
 104        switch (which) {
 105                case IOPRIO_WHO_PROCESS:
 106                        if (!who)
 107                                p = current;
 108                        else
 109                                p = find_task_by_vpid(who);
 110                        if (p)
 111                                ret = set_task_ioprio(p, ioprio);
 112                        break;
 113                case IOPRIO_WHO_PGRP:
 114                        if (!who)
 115                                pgrp = task_pgrp(current);
 116                        else
 117                                pgrp = find_vpid(who);
 118                        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 119                                ret = set_task_ioprio(p, ioprio);
 120                                if (ret)
 121                                        break;
 122                        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 123                        break;
 124                case IOPRIO_WHO_USER:
 125                        if (!who)
 126                                user = current->user;
 127                        else
 128                                user = find_user(who);
 129
 130                        if (!user)
 131                                break;
 132
 133                        do_each_thread(g, p) {
 134                                if (p->uid != who)
 135                                        continue;
 136                                ret = set_task_ioprio(p, ioprio);
 137                                if (ret)
 138                                        goto free_uid;
 139                        } while_each_thread(g, p);
 140free_uid:
 141                        if (who)
 142                                free_uid(user);
 143                        break;
 144                default:
 145                        ret = -EINVAL;
 146        }
 147
 148        read_unlock(&tasklist_lock);
 149        return ret;
 150}
 151
 152static int get_task_ioprio(struct task_struct *p)
 153{
 154        int ret;
 155
 156        ret = security_task_getioprio(p);
 157        if (ret)
 158                goto out;
 159        ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 160        if (p->io_context)
 161                ret = p->io_context->ioprio;
 162out:
 163        return ret;
 164}
 165
 166int ioprio_best(unsigned short aprio, unsigned short bprio)
 167{
 168        unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
 169        unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
 170
 171        if (aclass == IOPRIO_CLASS_NONE)
 172                aclass = IOPRIO_CLASS_BE;
 173        if (bclass == IOPRIO_CLASS_NONE)
 174                bclass = IOPRIO_CLASS_BE;
 175
 176        if (aclass == bclass)
 177                return min(aprio, bprio);
 178        if (aclass > bclass)
 179                return bprio;
 180        else
 181                return aprio;
 182}
 183
 184asmlinkage long sys_ioprio_get(int which, int who)
 185{
 186        struct task_struct *g, *p;
 187        struct user_struct *user;
 188        struct pid *pgrp;
 189        int ret = -ESRCH;
 190        int tmpio;
 191
 192        read_lock(&tasklist_lock);
 193        switch (which) {
 194                case IOPRIO_WHO_PROCESS:
 195                        if (!who)
 196                                p = current;
 197                        else
 198                                p = find_task_by_vpid(who);
 199                        if (p)
 200                                ret = get_task_ioprio(p);
 201                        break;
 202                case IOPRIO_WHO_PGRP:
 203                        if (!who)
 204                                pgrp = task_pgrp(current);
 205                        else
 206                                pgrp = find_vpid(who);
 207                        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 208                                tmpio = get_task_ioprio(p);
 209                                if (tmpio < 0)
 210                                        continue;
 211                                if (ret == -ESRCH)
 212                                        ret = tmpio;
 213                                else
 214                                        ret = ioprio_best(ret, tmpio);
 215                        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 216                        break;
 217                case IOPRIO_WHO_USER:
 218                        if (!who)
 219                                user = current->user;
 220                        else
 221                                user = find_user(who);
 222
 223                        if (!user)
 224                                break;
 225
 226                        do_each_thread(g, p) {
 227                                if (p->uid != user->uid)
 228                                        continue;
 229                                tmpio = get_task_ioprio(p);
 230                                if (tmpio < 0)
 231                                        continue;
 232                                if (ret == -ESRCH)
 233                                        ret = tmpio;
 234                                else
 235                                        ret = ioprio_best(ret, tmpio);
 236                        } while_each_thread(g, p);
 237
 238                        if (who)
 239                                free_uid(user);
 240                        break;
 241                default:
 242                        ret = -EINVAL;
 243        }
 244
 245        read_unlock(&tasklist_lock);
 246        return ret;
 247}
 248
 249