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/blkdev.h>
  27 #include <linux/capability.h>
  28 #include <linux/sched/user.h>
  29 #include <linux/syscalls.h>
  30 #include <linux/security.h>
  31 #include <linux/pid_namespace.h>
  32
  33 int set_task_ioprio(struct task_struct *task, int ioprio)
  34 {
  35         int err;
  36         struct io_context *ioc;
  37         const struct cred *cred = current_cred(), *tcred;
  38
  39         rcu_read_lock();
  40         tcred = __task_cred(task);
  41         if (!uid_eq(tcred->uid, cred->euid) &&
  42             !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
  43                 rcu_read_unlock();
  44                 return -EPERM;
  45         }
  46         rcu_read_unlock();
  47
  48         err = security_task_setioprio(task, ioprio);
  49         if (err)
  50                 return err;
  51
  52         ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
  53         if (ioc) {
  54                 ioc->ioprio = ioprio;
  55                 put_io_context(ioc);
  56         }
  57
  58         return err;
  59 }
  60 EXPORT_SYMBOL_GPL(set_task_ioprio);
  61
  62 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
  63 {
  64         int class = IOPRIO_PRIO_CLASS(ioprio);
  65         int data = IOPRIO_PRIO_DATA(ioprio);
  66         struct task_struct *p, *g;
  67         struct user_struct *user;
  68         struct pid *pgrp;
  69         kuid_t uid;
  70         int ret;
  71
  72         switch (class) {
  73                 case IOPRIO_CLASS_RT:
  74                         if (!capable(CAP_SYS_ADMIN))
  75                                 return -EPERM;
  76                         /* fall through, rt has prio field too */
  77                 case IOPRIO_CLASS_BE:
  78                         if (data >= IOPRIO_BE_NR || data < 0)
  79                                 return -EINVAL;
  80
  81                         break;
  82                 case IOPRIO_CLASS_IDLE:
  83                         break;
  84                 case IOPRIO_CLASS_NONE:
  85                         if (data)
  86                                 return -EINVAL;
  87                         break;
  88                 default:
  89                         return -EINVAL;
  90         }
  91
  92         ret = -ESRCH;
  93         rcu_read_lock();
  94         switch (which) {
  95                 case IOPRIO_WHO_PROCESS:
  96                         if (!who)
  97                                 p = current;
  98                         else
  99                                 p = find_task_by_vpid(who);
 100                         if (p)
 101                                 ret = set_task_ioprio(p, ioprio);
 102                         break;
 103                 case IOPRIO_WHO_PGRP:
 104                         if (!who)
 105                                 pgrp = task_pgrp(current);
 106                         else
 107                                 pgrp = find_vpid(who);
 108                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 109                                 ret = set_task_ioprio(p, ioprio);
 110                                 if (ret)
 111                                         break;
 112                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 113                         break;
 114                 case IOPRIO_WHO_USER:
 115                         uid = make_kuid(current_user_ns(), who);
 116                         if (!uid_valid(uid))
 117                                 break;
 118                         if (!who)
 119                                 user = current_user();
 120                         else
 121                                 user = find_user(uid);
 122
 123                         if (!user)
 124                                 break;
 125
 126                         for_each_process_thread(g, p) {
 127                                 if (!uid_eq(task_uid(p), uid) ||
 128                                     !task_pid_vnr(p))
 129                                         continue;
 130                                 ret = set_task_ioprio(p, ioprio);
 131                                 if (ret)
 132                                         goto free_uid;
 133                         }
 134 free_uid:
 135                         if (who)
 136                                 free_uid(user);
 137                         break;
 138                 default:
 139                         ret = -EINVAL;
 140         }
 141
 142         rcu_read_unlock();
 143         return ret;
 144 }
 145
 146 static int get_task_ioprio(struct task_struct *p)
 147 {
 148         int ret;
 149
 150         ret = security_task_getioprio(p);
 151         if (ret)
 152                 goto out;
 153         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 154         task_lock(p);
 155         if (p->io_context)
 156                 ret = p->io_context->ioprio;
 157         task_unlock(p);
 158 out:
 159         return ret;
 160 }
 161
 162 int ioprio_best(unsigned short aprio, unsigned short bprio)
 163 {
 164         unsigned short aclass;
 165         unsigned short bclass;
 166
 167         if (!ioprio_valid(aprio))
 168                 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 169         if (!ioprio_valid(bprio))
 170                 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 171
 172         aclass = IOPRIO_PRIO_CLASS(aprio);
 173         bclass = IOPRIO_PRIO_CLASS(bprio);
 174         if (aclass == bclass)
 175                 return min(aprio, bprio);
 176         if (aclass > bclass)
 177                 return bprio;
 178         else
 179                 return aprio;
 180 }
 181
 182 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 183 {
 184         struct task_struct *g, *p;
 185         struct user_struct *user;
 186         struct pid *pgrp;
 187         kuid_t uid;
 188         int ret = -ESRCH;
 189         int tmpio;
 190
 191         rcu_read_lock();
 192         switch (which) {
 193                 case IOPRIO_WHO_PROCESS:
 194                         if (!who)
 195                                 p = current;
 196                         else
 197                                 p = find_task_by_vpid(who);
 198                         if (p)
 199                                 ret = get_task_ioprio(p);
 200                         break;
 201                 case IOPRIO_WHO_PGRP:
 202                         if (!who)
 203                                 pgrp = task_pgrp(current);
 204                         else
 205                                 pgrp = find_vpid(who);
 206                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 207                                 tmpio = get_task_ioprio(p);
 208                                 if (tmpio < 0)
 209                                         continue;
 210                                 if (ret == -ESRCH)
 211                                         ret = tmpio;
 212                                 else
 213                                         ret = ioprio_best(ret, tmpio);
 214                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 215                         break;
 216                 case IOPRIO_WHO_USER:
 217                         uid = make_kuid(current_user_ns(), who);
 218                         if (!who)
 219                                 user = current_user();
 220                         else
 221                                 user = find_user(uid);
 222
 223                         if (!user)
 224                                 break;
 225
 226                         for_each_process_thread(g, p) {
 227                                 if (!uid_eq(task_uid(p), user->uid) ||
 228                                     !task_pid_vnr(p))
 229                                         continue;
 230                                 tmpio = get_task_ioprio(p);
 231                                 if (tmpio < 0)
 232                                         continue;
 233                                 if (ret == -ESRCH)
 234                                         ret = tmpio;
 235                                 else
 236                                         ret = ioprio_best(ret, tmpio);
 237                         }
 238
 239                         if (who)
 240                                 free_uid(user);
 241                         break;
 242                 default:
 243                         ret = -EINVAL;
 244         }
 245
 246         rcu_read_unlock();
 247         return ret;
 248 }