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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/syscalls.h>
  26
  27 static int set_task_ioprio(struct task_struct *task, int ioprio)
  28 {
  29         struct io_context *ioc;
  30
  31         if (task->uid != current->euid &&
  32             task->uid != current->uid && !capable(CAP_SYS_NICE))
  33                 return -EPERM;
  34
  35         task_lock(task);
  36
  37         task->ioprio = ioprio;
  38
  39         ioc = task->io_context;
  40         if (ioc && ioc->set_ioprio)
  41                 ioc->set_ioprio(ioc, ioprio);
  42
  43         task_unlock(task);
  44         return 0;
  45 }
  46
  47 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
  48 {
  49         int class = IOPRIO_PRIO_CLASS(ioprio);
  50         int data = IOPRIO_PRIO_DATA(ioprio);
  51         struct task_struct *p, *g;
  52         struct user_struct *user;
  53         int ret;
  54
  55         switch (class) {
  56                 case IOPRIO_CLASS_RT:
  57                         if (!capable(CAP_SYS_ADMIN))
  58                                 return -EPERM;
  59                         /* fall through, rt has prio field too */
  60                 case IOPRIO_CLASS_BE:
  61                         if (data >= IOPRIO_BE_NR || data < 0)
  62                                 return -EINVAL;
  63
  64                         break;
  65                 case IOPRIO_CLASS_IDLE:
  66                         if (!capable(CAP_SYS_ADMIN))
  67                                 return -EPERM;
  68                         break;
  69                 default:
  70                         return -EINVAL;
  71         }
  72
  73         ret = -ESRCH;
  74         read_lock_irq(&tasklist_lock);
  75         switch (which) {
  76                 case IOPRIO_WHO_PROCESS:
  77                         if (!who)
  78                                 p = current;
  79                         else
  80                                 p = find_task_by_pid(who);
  81                         if (p)
  82                                 ret = set_task_ioprio(p, ioprio);
  83                         break;
  84                 case IOPRIO_WHO_PGRP:
  85                         if (!who)
  86                                 who = process_group(current);
  87                         do_each_task_pid(who, PIDTYPE_PGID, p) {
  88                                 ret = set_task_ioprio(p, ioprio);
  89                                 if (ret)
  90                                         break;
  91                         } while_each_task_pid(who, PIDTYPE_PGID, p);
  92                         break;
  93                 case IOPRIO_WHO_USER:
  94                         if (!who)
  95                                 user = current->user;
  96                         else
  97                                 user = find_user(who);
  98
  99                         if (!user)
 100                                 break;
 101
 102                         do_each_thread(g, p) {
 103                                 if (p->uid != who)
 104                                         continue;
 105                                 ret = set_task_ioprio(p, ioprio);
 106                                 if (ret)
 107                                         break;
 108                         } while_each_thread(g, p);
 109
 110                         if (who)
 111                                 free_uid(user);
 112                         break;
 113                 default:
 114                         ret = -EINVAL;
 115         }
 116
 117         read_unlock_irq(&tasklist_lock);
 118         return ret;
 119 }
 120
 121 asmlinkage long sys_ioprio_get(int which, int who)
 122 {
 123         struct task_struct *g, *p;
 124         struct user_struct *user;
 125         int ret = -ESRCH;
 126
 127         read_lock_irq(&tasklist_lock);
 128         switch (which) {
 129                 case IOPRIO_WHO_PROCESS:
 130                         if (!who)
 131                                 p = current;
 132                         else
 133                                 p = find_task_by_pid(who);
 134                         if (p)
 135                                 ret = p->ioprio;
 136                         break;
 137                 case IOPRIO_WHO_PGRP:
 138                         if (!who)
 139                                 who = process_group(current);
 140                         do_each_task_pid(who, PIDTYPE_PGID, p) {
 141                                 if (ret == -ESRCH)
 142                                         ret = p->ioprio;
 143                                 else
 144                                         ret = ioprio_best(ret, p->ioprio);
 145                         } while_each_task_pid(who, PIDTYPE_PGID, p);
 146                         break;
 147                 case IOPRIO_WHO_USER:
 148                         if (!who)
 149                                 user = current->user;
 150                         else
 151                                 user = find_user(who);
 152
 153                         if (!user)
 154                                 break;
 155
 156                         do_each_thread(g, p) {
 157                                 if (p->uid != user->uid)
 158                                         continue;
 159                                 if (ret == -ESRCH)
 160                                         ret = p->ioprio;
 161                                 else
 162                                         ret = ioprio_best(ret, p->ioprio);
 163                         } while_each_thread(g, p);
 164
 165                         if (who)
 166                                 free_uid(user);
 167                         break;
 168                 default:
 169                         ret = -EINVAL;
 170         }
 171
 172         read_unlock_irq(&tasklist_lock);
 173         return ret;
 174 }
 175