fs/ioprio.c

   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/vs_cvirt.h>
  28
  29 static int set_task_ioprio(struct task_struct *task, int ioprio)
  30 {
  31         struct io_context *ioc;
  32
  33         if (task->uid != current->euid &&
  34             task->uid != current->uid && !capable(CAP_SYS_NICE))
  35                 return -EPERM;
  36
  37         task_lock(task);
  38
  39         task->ioprio = ioprio;
  40
  41         ioc = task->io_context;
  42         if (ioc && ioc->set_ioprio)
  43                 ioc->set_ioprio(ioc, ioprio);
  44
  45         task_unlock(task);
  46         return 0;
  47 }
  48
  49 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
  50 {
  51         int class = IOPRIO_PRIO_CLASS(ioprio);
  52         int data = IOPRIO_PRIO_DATA(ioprio);
  53         struct task_struct *p, *g;
  54         struct user_struct *user;
  55         int ret;
  56
  57         switch (class) {
  58                 case IOPRIO_CLASS_RT:
  59                         if (!capable(CAP_SYS_ADMIN))
  60                                 return -EPERM;
  61                         /* fall through, rt has prio field too */
  62                 case IOPRIO_CLASS_BE:
  63                         if (data >= IOPRIO_BE_NR || data < 0)
  64                                 return -EINVAL;
  65
  66                         break;
  67                 case IOPRIO_CLASS_IDLE:
  68                         if (!capable(CAP_SYS_ADMIN))
  69                                 return -EPERM;
  70                         break;
  71                 default:
  72                         return -EINVAL;
  73         }
  74
  75         ret = -ESRCH;
  76         read_lock_irq(&tasklist_lock);
  77         switch (which) {
  78                 case IOPRIO_WHO_PROCESS:
  79                         if (!who)
  80                                 p = current;
  81                         else
  82                                 p = find_task_by_pid(who);
  83                         if (p)
  84                                 ret = set_task_ioprio(p, ioprio);
  85                         break;
  86                 case IOPRIO_WHO_PGRP:
  87                         if (!who)
  88                                 who = process_group(current);
  89                         do_each_task_pid(who, PIDTYPE_PGID, p) {
  90                                 ret = set_task_ioprio(p, ioprio);
  91                                 if (ret)
  92                                         break;
  93                         } while_each_task_pid(who, PIDTYPE_PGID, p);
  94                         break;
  95                 case IOPRIO_WHO_USER:
  96                         if (!who)
  97                                 user = current->user;
  98                         else
  99                                 user = find_user(vx_current_xid(), who);
 100
 101                         if (!user)
 102                                 break;
 103
 104                         do_each_thread(g, p) {
 105                                 if (p->uid != who)
 106                                         continue;
 107                                 ret = set_task_ioprio(p, ioprio);
 108                                 if (ret)
 109                                         break;
 110                         } while_each_thread(g, p);
 111
 112                         if (who)
 113                                 free_uid(user);
 114                         break;
 115                 default:
 116                         ret = -EINVAL;
 117         }
 118
 119         read_unlock_irq(&tasklist_lock);
 120         return ret;
 121 }
 122
 123 asmlinkage long sys_ioprio_get(int which, int who)
 124 {
 125         struct task_struct *g, *p;
 126         struct user_struct *user;
 127         int ret = -ESRCH;
 128
 129         read_lock_irq(&tasklist_lock);
 130         switch (which) {
 131                 case IOPRIO_WHO_PROCESS:
 132                         if (!who)
 133                                 p = current;
 134                         else
 135                                 p = find_task_by_pid(who);
 136                         if (p)
 137                                 ret = p->ioprio;
 138                         break;
 139                 case IOPRIO_WHO_PGRP:
 140                         if (!who)
 141                                 who = process_group(current);
 142                         do_each_task_pid(who, PIDTYPE_PGID, p) {
 143                                 if (ret == -ESRCH)
 144                                         ret = p->ioprio;
 145                                 else
 146                                         ret = ioprio_best(ret, p->ioprio);
 147                         } while_each_task_pid(who, PIDTYPE_PGID, p);
 148                         break;
 149                 case IOPRIO_WHO_USER:
 150                         if (!who)
 151                                 user = current->user;
 152                         else
 153                                 user = find_user(vx_current_xid(), who);
 154
 155                         if (!user)
 156                                 break;
 157
 158                         do_each_thread(g, p) {
 159                                 if (p->uid != user->uid)
 160                                         continue;
 161                                 if (ret == -ESRCH)
 162                                         ret = p->ioprio;
 163                                 else
 164                                         ret = ioprio_best(ret, p->ioprio);
 165                         } while_each_thread(g, p);
 166
 167                         if (who)
 168                                 free_uid(user);
 169                         break;
 170                 default:
 171                         ret = -EINVAL;
 172         }
 173
 174         read_unlock_irq(&tasklist_lock);
 175         return ret;
 176 }
 177