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   1 /*
   2  * fs/ioprio.c
   3  *
   4  * Copyright (C) 2004 Jens Axboe <axboe@suse.de>
   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
  29 static int set_task_ioprio(struct task_struct *task, int ioprio)
  30 {
  31         int err;
  32         struct io_context *ioc;
  33
  34         if (task->uid != current->euid &&
  35             task->uid != current->uid && !capable(CAP_SYS_NICE))
  36                 return -EPERM;
  37
  38         err = security_task_setioprio(task, ioprio);
  39         if (err)
  40                 return err;
  41
  42         task_lock(task);
  43
  44         task->ioprio = ioprio;
  45
  46         ioc = task->io_context;
  47         if (ioc && ioc->set_ioprio)
  48                 ioc->set_ioprio(ioc, ioprio);
  49
  50         task_unlock(task);
  51         return 0;
  52 }
  53
  54 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
  55 {
  56         int class = IOPRIO_PRIO_CLASS(ioprio);
  57         int data = IOPRIO_PRIO_DATA(ioprio);
  58         struct task_struct *p, *g;
  59         struct user_struct *user;
  60         int ret;
  61
  62         switch (class) {
  63                 case IOPRIO_CLASS_RT:
  64                         if (!capable(CAP_SYS_ADMIN))
  65                                 return -EPERM;
  66                         /* fall through, rt has prio field too */
  67                 case IOPRIO_CLASS_BE:
  68                         if (data >= IOPRIO_BE_NR || data < 0)
  69                                 return -EINVAL;
  70
  71                         break;
  72                 case IOPRIO_CLASS_IDLE:
  73                         if (!capable(CAP_SYS_ADMIN))
  74                                 return -EPERM;
  75                         break;
  76                 default:
  77                         return -EINVAL;
  78         }
  79
  80         ret = -ESRCH;
  81         read_lock_irq(&tasklist_lock);
  82         switch (which) {
  83                 case IOPRIO_WHO_PROCESS:
  84                         if (!who)
  85                                 p = current;
  86                         else
  87                                 p = find_task_by_pid(who);
  88                         if (p)
  89                                 ret = set_task_ioprio(p, ioprio);
  90                         break;
  91                 case IOPRIO_WHO_PGRP:
  92                         if (!who)
  93                                 who = process_group(current);
  94                         do_each_task_pid(who, PIDTYPE_PGID, p) {
  95                                 ret = set_task_ioprio(p, ioprio);
  96                                 if (ret)
  97                                         break;
  98                         } while_each_task_pid(who, PIDTYPE_PGID, p);
  99                         break;
 100                 case IOPRIO_WHO_USER:
 101                         if (!who)
 102                                 user = current->user;
 103                         else
 104                                 user = find_user(who);
 105
 106                         if (!user)
 107                                 break;
 108
 109                         do_each_thread(g, p) {
 110                                 if (p->uid != who)
 111                                         continue;
 112                                 ret = set_task_ioprio(p, ioprio);
 113                                 if (ret)
 114                                         break;
 115                         } while_each_thread(g, p);
 116
 117                         if (who)
 118                                 free_uid(user);
 119                         break;
 120                 default:
 121                         ret = -EINVAL;
 122         }
 123
 124         read_unlock_irq(&tasklist_lock);
 125         return ret;
 126 }
 127
 128 asmlinkage long sys_ioprio_get(int which, int who)
 129 {
 130         struct task_struct *g, *p;
 131         struct user_struct *user;
 132         int ret = -ESRCH;
 133
 134         read_lock_irq(&tasklist_lock);
 135         switch (which) {
 136                 case IOPRIO_WHO_PROCESS:
 137                         if (!who)
 138                                 p = current;
 139                         else
 140                                 p = find_task_by_pid(who);
 141                         if (p)
 142                                 ret = p->ioprio;
 143                         break;
 144                 case IOPRIO_WHO_PGRP:
 145                         if (!who)
 146                                 who = process_group(current);
 147                         do_each_task_pid(who, PIDTYPE_PGID, p) {
 148                                 if (ret == -ESRCH)
 149                                         ret = p->ioprio;
 150                                 else
 151                                         ret = ioprio_best(ret, p->ioprio);
 152                         } while_each_task_pid(who, PIDTYPE_PGID, p);
 153                         break;
 154                 case IOPRIO_WHO_USER:
 155                         if (!who)
 156                                 user = current->user;
 157                         else
 158                                 user = find_user(who);
 159
 160                         if (!user)
 161                                 break;
 162
 163                         do_each_thread(g, p) {
 164                                 if (p->uid != user->uid)
 165                                         continue;
 166                                 if (ret == -ESRCH)
 167                                         ret = p->ioprio;
 168                                 else
 169                                         ret = ioprio_best(ret, p->ioprio);
 170                         } while_each_thread(g, p);
 171
 172                         if (who)
 173                                 free_uid(user);
 174                         break;
 175                 default:
 176                         ret = -EINVAL;
 177         }
 178
 179         read_unlock_irq(&tasklist_lock);
 180         return ret;
 181 }
 182