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/security.h>
  28 #include <linux/vs_base.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
  45         task->ioprio = ioprio;
  46
  47         ioc = task->io_context;
  48         /* see wmb() in current_io_context() */
  49         smp_read_barrier_depends();
  50
  51         if (ioc && ioc->set_ioprio)
  52                 ioc->set_ioprio(ioc, ioprio);
  53
  54         task_unlock(task);
  55         return 0;
  56 }
  57
  58 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
  59 {
  60         int class = IOPRIO_PRIO_CLASS(ioprio);
  61         int data = IOPRIO_PRIO_DATA(ioprio);
  62         struct task_struct *p, *g;
  63         struct user_struct *user;
  64         int ret;
  65
  66         switch (class) {
  67                 case IOPRIO_CLASS_RT:
  68                         if (!capable(CAP_SYS_ADMIN))
  69                                 return -EPERM;
  70                         /* fall through, rt has prio field too */
  71                 case IOPRIO_CLASS_BE:
  72                         if (data >= IOPRIO_BE_NR || data < 0)
  73                                 return -EINVAL;
  74
  75                         break;
  76                 case IOPRIO_CLASS_IDLE:
  77                         if (!capable(CAP_SYS_ADMIN))
  78                                 return -EPERM;
  79                         break;
  80                 default:
  81                         return -EINVAL;
  82         }
  83
  84         ret = -ESRCH;
  85         read_lock_irq(&tasklist_lock);
  86         switch (which) {
  87                 case IOPRIO_WHO_PROCESS:
  88                         if (!who)
  89                                 p = current;
  90                         else
  91                                 p = find_task_by_pid(who);
  92                         if (p)
  93                                 ret = set_task_ioprio(p, ioprio);
  94                         break;
  95                 case IOPRIO_WHO_PGRP:
  96                         if (!who)
  97                                 who = process_group(current);
  98                         do_each_task_pid(who, PIDTYPE_PGID, p) {
  99                                 ret = set_task_ioprio(p, ioprio);
 100                                 if (ret)
 101                                         break;
 102                         } while_each_task_pid(who, PIDTYPE_PGID, p);
 103                         break;
 104                 case IOPRIO_WHO_USER:
 105                         if (!who)
 106                                 user = current->user;
 107                         else
 108                                 user = find_user(vx_current_xid(), who);
 109
 110                         if (!user)
 111                                 break;
 112
 113                         do_each_thread(g, p) {
 114                                 if (p->uid != who)
 115                                         continue;
 116                                 ret = set_task_ioprio(p, ioprio);
 117                                 if (ret)
 118                                         goto free_uid;
 119                         } while_each_thread(g, p);
 120 free_uid:
 121                         if (who)
 122                                 free_uid(user);
 123                         break;
 124                 default:
 125                         ret = -EINVAL;
 126         }
 127
 128         read_unlock_irq(&tasklist_lock);
 129         return ret;
 130 }
 131
 132 static int get_task_ioprio(struct task_struct *p)
 133 {
 134         int ret;
 135
 136         ret = security_task_getioprio(p);
 137         if (ret)
 138                 goto out;
 139         ret = p->ioprio;
 140 out:
 141         return ret;
 142 }
 143
 144 int ioprio_best(unsigned short aprio, unsigned short bprio)
 145 {
 146         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
 147         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
 148
 149         if (!ioprio_valid(aprio))
 150                 return bprio;
 151         if (!ioprio_valid(bprio))
 152                 return aprio;
 153
 154         if (aclass == IOPRIO_CLASS_NONE)
 155                 aclass = IOPRIO_CLASS_BE;
 156         if (bclass == IOPRIO_CLASS_NONE)
 157                 bclass = IOPRIO_CLASS_BE;
 158
 159         if (aclass == bclass)
 160                 return min(aprio, bprio);
 161         if (aclass > bclass)
 162                 return bprio;
 163         else
 164                 return aprio;
 165 }
 166
 167 asmlinkage long sys_ioprio_get(int which, int who)
 168 {
 169         struct task_struct *g, *p;
 170         struct user_struct *user;
 171         int ret = -ESRCH;
 172         int tmpio;
 173
 174         read_lock_irq(&tasklist_lock);
 175         switch (which) {
 176                 case IOPRIO_WHO_PROCESS:
 177                         if (!who)
 178                                 p = current;
 179                         else
 180                                 p = find_task_by_pid(who);
 181                         if (p)
 182                                 ret = get_task_ioprio(p);
 183                         break;
 184                 case IOPRIO_WHO_PGRP:
 185                         if (!who)
 186                                 who = process_group(current);
 187                         do_each_task_pid(who, PIDTYPE_PGID, p) {
 188                                 tmpio = get_task_ioprio(p);
 189                                 if (tmpio < 0)
 190                                         continue;
 191                                 if (ret == -ESRCH)
 192                                         ret = tmpio;
 193                                 else
 194                                         ret = ioprio_best(ret, tmpio);
 195                         } while_each_task_pid(who, PIDTYPE_PGID, p);
 196                         break;
 197                 case IOPRIO_WHO_USER:
 198                         if (!who)
 199                                 user = current->user;
 200                         else
 201                                 user = find_user(vx_current_xid(), who);
 202
 203                         if (!user)
 204                                 break;
 205
 206                         do_each_thread(g, p) {
 207                                 if (p->uid != user->uid)
 208                                         continue;
 209                                 tmpio = get_task_ioprio(p);
 210                                 if (tmpio < 0)
 211                                         continue;
 212                                 if (ret == -ESRCH)
 213                                         ret = tmpio;
 214                                 else
 215                                         ret = ioprio_best(ret, tmpio);
 216                         } while_each_thread(g, p);
 217
 218                         if (who)
 219                                 free_uid(user);
 220                         break;
 221                 default:
 222                         ret = -EINVAL;
 223         }
 224
 225         read_unlock_irq(&tasklist_lock);
 226         return ret;
 227 }
 228