err.no Git - linux-2.6/blob - 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
  30 static 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
  68 asmlinkage 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                         if (!capable(CAP_SYS_ADMIN))
  89                                 return -EPERM;
  90                         break;
  91                 case IOPRIO_CLASS_NONE:
  92                         if (data)
  93                                 return -EINVAL;
  94                         break;
  95                 default:
  96                         return -EINVAL;
  97         }
  98
  99         ret = -ESRCH;
 100         /*
 101          * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
 102          * so we can't use rcu_read_lock(). See re-copy of ->ioprio
 103          * in copy_process().
 104          */
 105         read_lock(&tasklist_lock);
 106         switch (which) {
 107                 case IOPRIO_WHO_PROCESS:
 108                         if (!who)
 109                                 p = current;
 110                         else
 111                                 p = find_task_by_vpid(who);
 112                         if (p)
 113                                 ret = set_task_ioprio(p, ioprio);
 114                         break;
 115                 case IOPRIO_WHO_PGRP:
 116                         if (!who)
 117                                 pgrp = task_pgrp(current);
 118                         else
 119                                 pgrp = find_vpid(who);
 120                         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 121                                 ret = set_task_ioprio(p, ioprio);
 122                                 if (ret)
 123                                         break;
 124                         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 125                         break;
 126                 case IOPRIO_WHO_USER:
 127                         if (!who)
 128                                 user = current->user;
 129                         else
 130                                 user = find_user(who);
 131
 132                         if (!user)
 133                                 break;
 134
 135                         do_each_thread(g, p) {
 136                                 if (p->uid != who)
 137                                         continue;
 138                                 ret = set_task_ioprio(p, ioprio);
 139                                 if (ret)
 140                                         goto free_uid;
 141                         } while_each_thread(g, p);
 142 free_uid:
 143                         if (who)
 144                                 free_uid(user);
 145                         break;
 146                 default:
 147                         ret = -EINVAL;
 148         }
 149
 150         read_unlock(&tasklist_lock);
 151         return ret;
 152 }
 153
 154 static int get_task_ioprio(struct task_struct *p)
 155 {
 156         int ret;
 157
 158         ret = security_task_getioprio(p);
 159         if (ret)
 160                 goto out;
 161         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 162         if (p->io_context)
 163                 ret = p->io_context->ioprio;
 164 out:
 165         return ret;
 166 }
 167
 168 int ioprio_best(unsigned short aprio, unsigned short bprio)
 169 {
 170         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
 171         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
 172
 173         if (aclass == IOPRIO_CLASS_NONE)
 174                 aclass = IOPRIO_CLASS_BE;
 175         if (bclass == IOPRIO_CLASS_NONE)
 176                 bclass = IOPRIO_CLASS_BE;
 177
 178         if (aclass == bclass)
 179                 return min(aprio, bprio);
 180         if (aclass > bclass)
 181                 return bprio;
 182         else
 183                 return aprio;
 184 }
 185
 186 asmlinkage long sys_ioprio_get(int which, int who)
 187 {
 188         struct task_struct *g, *p;
 189         struct user_struct *user;
 190         struct pid *pgrp;
 191         int ret = -ESRCH;
 192         int tmpio;
 193
 194         read_lock(&tasklist_lock);
 195         switch (which) {
 196                 case IOPRIO_WHO_PROCESS:
 197                         if (!who)
 198                                 p = current;
 199                         else
 200                                 p = find_task_by_vpid(who);
 201                         if (p)
 202                                 ret = get_task_ioprio(p);
 203                         break;
 204                 case IOPRIO_WHO_PGRP:
 205                         if (!who)
 206                                 pgrp = task_pgrp(current);
 207                         else
 208                                 pgrp = find_vpid(who);
 209                         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 210                                 tmpio = get_task_ioprio(p);
 211                                 if (tmpio < 0)
 212                                         continue;
 213                                 if (ret == -ESRCH)
 214                                         ret = tmpio;
 215                                 else
 216                                         ret = ioprio_best(ret, tmpio);
 217                         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 218                         break;
 219                 case IOPRIO_WHO_USER:
 220                         if (!who)
 221                                 user = current->user;
 222                         else
 223                                 user = find_user(who);
 224
 225                         if (!user)
 226                                 break;
 227
 228                         do_each_thread(g, p) {
 229                                 if (p->uid != user->uid)
 230                                         continue;
 231                                 tmpio = get_task_ioprio(p);
 232                                 if (tmpio < 0)
 233                                         continue;
 234                                 if (ret == -ESRCH)
 235                                         ret = tmpio;
 236                                 else
 237                                         ret = ioprio_best(ret, tmpio);
 238                         } while_each_thread(g, p);
 239
 240                         if (who)
 241                                 free_uid(user);
 242                         break;
 243                 default:
 244                         ret = -EINVAL;
 245         }
 246
 247         read_unlock(&tasklist_lock);
 248         return ret;
 249 }
 250