block/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/cred.h>
  27 #include <linux/blkdev.h>
  28 #include <linux/capability.h>
  29 #include <linux/sched/user.h>
  30 #include <linux/sched/task.h>
  31 #include <linux/syscalls.h>
  32 #include <linux/security.h>
  33 #include <linux/pid_namespace.h>
  34
  35 int set_task_ioprio(struct task_struct *task, int ioprio)
  36 {
  37         int err;
  38         struct io_context *ioc;
  39         const struct cred *cred = current_cred(), *tcred;
  40
  41         rcu_read_lock();
  42         tcred = __task_cred(task);
  43         if (!uid_eq(tcred->uid, cred->euid) &&
  44             !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
  45                 rcu_read_unlock();
  46                 return -EPERM;
  47         }
  48         rcu_read_unlock();
  49
  50         err = security_task_setioprio(task, ioprio);
  51         if (err)
  52                 return err;
  53
  54         ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
  55         if (ioc) {
  56                 ioc->ioprio = ioprio;
  57                 put_io_context(ioc);
  58         }
  59
  60         return err;
  61 }
  62 EXPORT_SYMBOL_GPL(set_task_ioprio);
  63
  64 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
  65 {
  66         int class = IOPRIO_PRIO_CLASS(ioprio);
  67         int data = IOPRIO_PRIO_DATA(ioprio);
  68         struct task_struct *p, *g;
  69         struct user_struct *user;
  70         struct pid *pgrp;
  71         kuid_t uid;
  72         int ret;
  73
  74         switch (class) {
  75                 case IOPRIO_CLASS_RT:
  76                         if (!capable(CAP_SYS_ADMIN))
  77                                 return -EPERM;
  78                         /* fall through, rt has prio field too */
  79                 case IOPRIO_CLASS_BE:
  80                         if (data >= IOPRIO_BE_NR || data < 0)
  81                                 return -EINVAL;
  82
  83                         break;
  84                 case IOPRIO_CLASS_IDLE:
  85                         break;
  86                 case IOPRIO_CLASS_NONE:
  87                         if (data)
  88                                 return -EINVAL;
  89                         break;
  90                 default:
  91                         return -EINVAL;
  92         }
  93
  94         ret = -ESRCH;
  95         rcu_read_lock();
  96         switch (which) {
  97                 case IOPRIO_WHO_PROCESS:
  98                         if (!who)
  99                                 p = current;
 100                         else
 101                                 p = find_task_by_vpid(who);
 102                         if (p)
 103                                 ret = set_task_ioprio(p, ioprio);
 104                         break;
 105                 case IOPRIO_WHO_PGRP:
 106                         if (!who)
 107                                 pgrp = task_pgrp(current);
 108                         else
 109                                 pgrp = find_vpid(who);
 110                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 111                                 ret = set_task_ioprio(p, ioprio);
 112                                 if (ret)
 113                                         break;
 114                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 115                         break;
 116                 case IOPRIO_WHO_USER:
 117                         uid = make_kuid(current_user_ns(), who);
 118                         if (!uid_valid(uid))
 119                                 break;
 120                         if (!who)
 121                                 user = current_user();
 122                         else
 123                                 user = find_user(uid);
 124
 125                         if (!user)
 126                                 break;
 127
 128                         for_each_process_thread(g, p) {
 129                                 if (!uid_eq(task_uid(p), uid) ||
 130                                     !task_pid_vnr(p))
 131                                         continue;
 132                                 ret = set_task_ioprio(p, ioprio);
 133                                 if (ret)
 134                                         goto free_uid;
 135                         }
 136 free_uid:
 137                         if (who)
 138                                 free_uid(user);
 139                         break;
 140                 default:
 141                         ret = -EINVAL;
 142         }
 143
 144         rcu_read_unlock();
 145         return ret;
 146 }
 147
 148 static int get_task_ioprio(struct task_struct *p)
 149 {
 150         int ret;
 151
 152         ret = security_task_getioprio(p);
 153         if (ret)
 154                 goto out;
 155         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 156         task_lock(p);
 157         if (p->io_context)
 158                 ret = p->io_context->ioprio;
 159         task_unlock(p);
 160 out:
 161         return ret;
 162 }
 163
 164 int ioprio_best(unsigned short aprio, unsigned short bprio)
 165 {
 166         if (!ioprio_valid(aprio))
 167                 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 168         if (!ioprio_valid(bprio))
 169                 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 170
 171         return min(aprio, bprio);
 172 }
 173
 174 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 175 {
 176         struct task_struct *g, *p;
 177         struct user_struct *user;
 178         struct pid *pgrp;
 179         kuid_t uid;
 180         int ret = -ESRCH;
 181         int tmpio;
 182
 183         rcu_read_lock();
 184         switch (which) {
 185                 case IOPRIO_WHO_PROCESS:
 186                         if (!who)
 187                                 p = current;
 188                         else
 189                                 p = find_task_by_vpid(who);
 190                         if (p)
 191                                 ret = get_task_ioprio(p);
 192                         break;
 193                 case IOPRIO_WHO_PGRP:
 194                         if (!who)
 195                                 pgrp = task_pgrp(current);
 196                         else
 197                                 pgrp = find_vpid(who);
 198                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 199                                 tmpio = get_task_ioprio(p);
 200                                 if (tmpio < 0)
 201                                         continue;
 202                                 if (ret == -ESRCH)
 203                                         ret = tmpio;
 204                                 else
 205                                         ret = ioprio_best(ret, tmpio);
 206                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 207                         break;
 208                 case IOPRIO_WHO_USER:
 209                         uid = make_kuid(current_user_ns(), who);
 210                         if (!who)
 211                                 user = current_user();
 212                         else
 213                                 user = find_user(uid);
 214
 215                         if (!user)
 216                                 break;
 217
 218                         for_each_process_thread(g, p) {
 219                                 if (!uid_eq(task_uid(p), user->uid) ||
 220                                     !task_pid_vnr(p))
 221                                         continue;
 222                                 tmpio = get_task_ioprio(p);
 223                                 if (tmpio < 0)
 224                                         continue;
 225                                 if (ret == -ESRCH)
 226                                         ret = tmpio;
 227                                 else
 228                                         ret = ioprio_best(ret, tmpio);
 229                         }
 230
 231                         if (who)
 232                                 free_uid(user);
 233                         break;
 234                 default:
 235                         ret = -EINVAL;
 236         }
 237
 238         rcu_read_unlock();
 239         return ret;
 240 }