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