linux/fs/ioprio.c
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   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/gfp.h>
  23#include <linux/kernel.h>
  24#include <linux/export.h>
  25#include <linux/ioprio.h>
  26#include <linux/blkdev.h>
  27#include <linux/capability.h>
  28#include <linux/syscalls.h>
  29#include <linux/security.h>
  30#include <linux/pid_namespace.h>
  31
  32int set_task_ioprio(struct task_struct *task, int ioprio)
  33{
  34        int err;
  35        struct io_context *ioc;
  36        const struct cred *cred = current_cred(), *tcred;
  37
  38        rcu_read_lock();
  39        tcred = __task_cred(task);
  40        if (!uid_eq(tcred->uid, cred->euid) &&
  41            !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
  42                rcu_read_unlock();
  43                return -EPERM;
  44        }
  45        rcu_read_unlock();
  46
  47        err = security_task_setioprio(task, ioprio);
  48        if (err)
  49                return err;
  50
  51        ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
  52        if (ioc) {
  53                ioc->ioprio = ioprio;
  54                put_io_context(ioc);
  55        }
  56
  57        return err;
  58}
  59EXPORT_SYMBOL_GPL(set_task_ioprio);
  60
  61SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
  62{
  63        int class = IOPRIO_PRIO_CLASS(ioprio);
  64        int data = IOPRIO_PRIO_DATA(ioprio);
  65        struct task_struct *p, *g;
  66        struct user_struct *user;
  67        struct pid *pgrp;
  68        kuid_t uid;
  69        int ret;
  70
  71        switch (class) {
  72                case IOPRIO_CLASS_RT:
  73                        if (!capable(CAP_SYS_ADMIN))
  74                                return -EPERM;
  75                        /* fall through, rt has prio field too */
  76                case IOPRIO_CLASS_BE:
  77                        if (data >= IOPRIO_BE_NR || data < 0)
  78                                return -EINVAL;
  79
  80                        break;
  81                case IOPRIO_CLASS_IDLE:
  82                        break;
  83                case IOPRIO_CLASS_NONE:
  84                        if (data)
  85                                return -EINVAL;
  86                        break;
  87                default:
  88                        return -EINVAL;
  89        }
  90
  91        ret = -ESRCH;
  92        rcu_read_lock();
  93        switch (which) {
  94                case IOPRIO_WHO_PROCESS:
  95                        if (!who)
  96                                p = current;
  97                        else
  98                                p = find_task_by_vpid(who);
  99                        if (p)
 100                                ret = set_task_ioprio(p, ioprio);
 101                        break;
 102                case IOPRIO_WHO_PGRP:
 103                        if (!who)
 104                                pgrp = task_pgrp(current);
 105                        else
 106                                pgrp = find_vpid(who);
 107                        do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 108                                ret = set_task_ioprio(p, ioprio);
 109                                if (ret)
 110                                        break;
 111                        } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 112                        break;
 113                case IOPRIO_WHO_USER:
 114                        uid = make_kuid(current_user_ns(), who);
 115                        if (!uid_valid(uid))
 116                                break;
 117                        if (!who)
 118                                user = current_user();
 119                        else
 120                                user = find_user(uid);
 121
 122                        if (!user)
 123                                break;
 124
 125                        do_each_thread(g, p) {
 126                                if (!uid_eq(task_uid(p), uid))
 127                                        continue;
 128                                ret = set_task_ioprio(p, ioprio);
 129                                if (ret)
 130                                        goto free_uid;
 131                        } while_each_thread(g, p);
 132free_uid:
 133                        if (who)
 134                                free_uid(user);
 135                        break;
 136                default:
 137                        ret = -EINVAL;
 138        }
 139
 140        rcu_read_unlock();
 141        return ret;
 142}
 143
 144static int get_task_ioprio(struct task_struct *p)
 145{
 146        int ret;
 147
 148        ret = security_task_getioprio(p);
 149        if (ret)
 150                goto out;
 151        ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 152        if (p->io_context)
 153                ret = p->io_context->ioprio;
 154out:
 155        return ret;
 156}
 157
 158int ioprio_best(unsigned short aprio, unsigned short bprio)
 159{
 160        unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
 161        unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
 162
 163        if (aclass == IOPRIO_CLASS_NONE)
 164                aclass = IOPRIO_CLASS_BE;
 165        if (bclass == IOPRIO_CLASS_NONE)
 166                bclass = IOPRIO_CLASS_BE;
 167
 168        if (aclass == bclass)
 169                return min(aprio, bprio);
 170        if (aclass > bclass)
 171                return bprio;
 172        else
 173                return aprio;
 174}
 175
 176SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 177{
 178        struct task_struct *g, *p;
 179        struct user_struct *user;
 180        struct pid *pgrp;
 181        kuid_t uid;
 182        int ret = -ESRCH;
 183        int tmpio;
 184
 185        rcu_read_lock();
 186        switch (which) {
 187                case IOPRIO_WHO_PROCESS:
 188                        if (!who)
 189                                p = current;
 190                        else
 191                                p = find_task_by_vpid(who);
 192                        if (p)
 193                                ret = get_task_ioprio(p);
 194                        break;
 195                case IOPRIO_WHO_PGRP:
 196                        if (!who)
 197                                pgrp = task_pgrp(current);
 198                        else
 199                                pgrp = find_vpid(who);
 200                        do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 201                                tmpio = get_task_ioprio(p);
 202                                if (tmpio < 0)
 203                                        continue;
 204                                if (ret == -ESRCH)
 205                                        ret = tmpio;
 206                                else
 207                                        ret = ioprio_best(ret, tmpio);
 208                        } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 209                        break;
 210                case IOPRIO_WHO_USER:
 211                        uid = make_kuid(current_user_ns(), who);
 212                        if (!who)
 213                                user = current_user();
 214                        else
 215                                user = find_user(uid);
 216
 217                        if (!user)
 218                                break;
 219
 220                        do_each_thread(g, p) {
 221                                if (!uid_eq(task_uid(p), user->uid))
 222                                        continue;
 223                                tmpio = get_task_ioprio(p);
 224                                if (tmpio < 0)
 225                                        continue;
 226                                if (ret == -ESRCH)
 227                                        ret = tmpio;
 228                                else
 229                                        ret = ioprio_best(ret, tmpio);
 230                        } while_each_thread(g, p);
 231
 232                        if (who)
 233                                free_uid(user);
 234                        break;
 235                default:
 236                        ret = -EINVAL;
 237        }
 238
 239        rcu_read_unlock();
 240        return ret;
 241}
 242
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