fs/ioprio.c

   1 /*
   2  * fs/ioprio.c
   3  *
   4  * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
   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/gfp.h>
  23 #include <linux/kernel.h>
  24 #include <linux/export.h>
  25 #include <linux/ioprio.h>
  26 #include <linux/blkdev.h>
  27 #include <linux/capability.h>
  28 #include <linux/syscalls.h>
  29 #include <linux/security.h>
  30 #include <linux/pid_namespace.h>
  31
  32 int set_task_ioprio(struct task_struct *task, int ioprio)
  33 {
  34         int err;
  35         struct io_context *ioc;
  36         const struct cred *cred = current_cred(), *tcred;
  37
  38         rcu_read_lock();
  39         tcred = __task_cred(task);
  40         if (tcred->uid != cred->euid &&
  41             tcred->uid != cred->uid && !capable(CAP_SYS_NICE)) {
  42                 rcu_read_unlock();
  43                 return -EPERM;
  44         }
  45         rcu_read_unlock();
  46
  47         err = security_task_setioprio(task, ioprio);
  48         if (err)
  49                 return err;
  50
  51         ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
  52         if (ioc) {
  53                 ioc_ioprio_changed(ioc, ioprio);
  54                 put_io_context(ioc, NULL);
  55         }
  56
  57         return err;
  58 }
  59 EXPORT_SYMBOL_GPL(set_task_ioprio);
  60
  61 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
  62 {
  63         int class = IOPRIO_PRIO_CLASS(ioprio);
  64         int data = IOPRIO_PRIO_DATA(ioprio);
  65         struct task_struct *p, *g;
  66         struct user_struct *user;
  67         struct pid *pgrp;
  68         int ret;
  69
  70         switch (class) {
  71                 case IOPRIO_CLASS_RT:
  72                         if (!capable(CAP_SYS_ADMIN))
  73                                 return -EPERM;
  74                         /* fall through, rt has prio field too */
  75                 case IOPRIO_CLASS_BE:
  76                         if (data >= IOPRIO_BE_NR || data < 0)
  77                                 return -EINVAL;
  78
  79                         break;
  80                 case IOPRIO_CLASS_IDLE:
  81                         break;
  82                 case IOPRIO_CLASS_NONE:
  83                         if (data)
  84                                 return -EINVAL;
  85                         break;
  86                 default:
  87                         return -EINVAL;
  88         }
  89
  90         ret = -ESRCH;
  91         rcu_read_lock();
  92         switch (which) {
  93                 case IOPRIO_WHO_PROCESS:
  94                         if (!who)
  95                                 p = current;
  96                         else
  97                                 p = find_task_by_vpid(who);
  98                         if (p)
  99                                 ret = set_task_ioprio(p, ioprio);
 100                         break;
 101                 case IOPRIO_WHO_PGRP:
 102                         if (!who)
 103                                 pgrp = task_pgrp(current);
 104                         else
 105                                 pgrp = find_vpid(who);
 106                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 107                                 ret = set_task_ioprio(p, ioprio);
 108                                 if (ret)
 109                                         break;
 110                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 111                         break;
 112                 case IOPRIO_WHO_USER:
 113                         if (!who)
 114                                 user = current_user();
 115                         else
 116                                 user = find_user(who);
 117
 118                         if (!user)
 119                                 break;
 120
 121                         do_each_thread(g, p) {
 122                                 if (__task_cred(p)->uid != who)
 123                                         continue;
 124                                 ret = set_task_ioprio(p, ioprio);
 125                                 if (ret)
 126                                         goto free_uid;
 127                         } while_each_thread(g, p);
 128 free_uid:
 129                         if (who)
 130                                 free_uid(user);
 131                         break;
 132                 default:
 133                         ret = -EINVAL;
 134         }
 135
 136         rcu_read_unlock();
 137         return ret;
 138 }
 139
 140 static int get_task_ioprio(struct task_struct *p)
 141 {
 142         int ret;
 143
 144         ret = security_task_getioprio(p);
 145         if (ret)
 146                 goto out;
 147         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 148         if (p->io_context)
 149                 ret = p->io_context->ioprio;
 150 out:
 151         return ret;
 152 }
 153
 154 int ioprio_best(unsigned short aprio, unsigned short bprio)
 155 {
 156         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
 157         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
 158
 159         if (aclass == IOPRIO_CLASS_NONE)
 160                 aclass = IOPRIO_CLASS_BE;
 161         if (bclass == IOPRIO_CLASS_NONE)
 162                 bclass = IOPRIO_CLASS_BE;
 163
 164         if (aclass == bclass)
 165                 return min(aprio, bprio);
 166         if (aclass > bclass)
 167                 return bprio;
 168         else
 169                 return aprio;
 170 }
 171
 172 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 173 {
 174         struct task_struct *g, *p;
 175         struct user_struct *user;
 176         struct pid *pgrp;
 177         int ret = -ESRCH;
 178         int tmpio;
 179
 180         rcu_read_lock();
 181         switch (which) {
 182                 case IOPRIO_WHO_PROCESS:
 183                         if (!who)
 184                                 p = current;
 185                         else
 186                                 p = find_task_by_vpid(who);
 187                         if (p)
 188                                 ret = get_task_ioprio(p);
 189                         break;
 190                 case IOPRIO_WHO_PGRP:
 191                         if (!who)
 192                                 pgrp = task_pgrp(current);
 193                         else
 194                                 pgrp = find_vpid(who);
 195                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 196                                 tmpio = get_task_ioprio(p);
 197                                 if (tmpio < 0)
 198                                         continue;
 199                                 if (ret == -ESRCH)
 200                                         ret = tmpio;
 201                                 else
 202                                         ret = ioprio_best(ret, tmpio);
 203                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 204                         break;
 205                 case IOPRIO_WHO_USER:
 206                         if (!who)
 207                                 user = current_user();
 208                         else
 209                                 user = find_user(who);
 210
 211                         if (!user)
 212                                 break;
 213
 214                         do_each_thread(g, p) {
 215                                 if (__task_cred(p)->uid != user->uid)
 216                                         continue;
 217                                 tmpio = get_task_ioprio(p);
 218                                 if (tmpio < 0)
 219                                         continue;
 220                                 if (ret == -ESRCH)
 221                                         ret = tmpio;
 222                                 else
 223                                         ret = ioprio_best(ret, tmpio);
 224                         } while_each_thread(g, p);
 225
 226                         if (who)
 227                                 free_uid(user);
 228                         break;
 229                 default:
 230                         ret = -EINVAL;
 231         }
 232
 233         rcu_read_unlock();
 234         return ret;
 235 }