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 int ioprio_check_cap(int ioprio)
  65 {
  66         int class = IOPRIO_PRIO_CLASS(ioprio);
  67         int data = IOPRIO_PRIO_DATA(ioprio);
  68
  69         switch (class) {
  70                 case IOPRIO_CLASS_RT:
  71                         if (!capable(CAP_SYS_ADMIN))
  72                                 return -EPERM;
  73                         /* fall through */
  74                         /* 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         return 0;
  91 }
  92
  93 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
  94 {
  95         struct task_struct *p, *g;
  96         struct user_struct *user;
  97         struct pid *pgrp;
  98         kuid_t uid;
  99         int ret;
 100
 101         ret = ioprio_check_cap(ioprio);
 102         if (ret)
 103                 return ret;
 104
 105         ret = -ESRCH;
 106         rcu_read_lock();
 107         switch (which) {
 108                 case IOPRIO_WHO_PROCESS:
 109                         if (!who)
 110                                 p = current;
 111                         else
 112                                 p = find_task_by_vpid(who);
 113                         if (p)
 114                                 ret = set_task_ioprio(p, ioprio);
 115                         break;
 116                 case IOPRIO_WHO_PGRP:
 117                         if (!who)
 118                                 pgrp = task_pgrp(current);
 119                         else
 120                                 pgrp = find_vpid(who);
 121                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 122                                 ret = set_task_ioprio(p, ioprio);
 123                                 if (ret)
 124                                         break;
 125                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 126                         break;
 127                 case IOPRIO_WHO_USER:
 128                         uid = make_kuid(current_user_ns(), who);
 129                         if (!uid_valid(uid))
 130                                 break;
 131                         if (!who)
 132                                 user = current_user();
 133                         else
 134                                 user = find_user(uid);
 135
 136                         if (!user)
 137                                 break;
 138
 139                         for_each_process_thread(g, p) {
 140                                 if (!uid_eq(task_uid(p), uid) ||
 141                                     !task_pid_vnr(p))
 142                                         continue;
 143                                 ret = set_task_ioprio(p, ioprio);
 144                                 if (ret)
 145                                         goto free_uid;
 146                         }
 147 free_uid:
 148                         if (who)
 149                                 free_uid(user);
 150                         break;
 151                 default:
 152                         ret = -EINVAL;
 153         }
 154
 155         rcu_read_unlock();
 156         return ret;
 157 }
 158
 159 static int get_task_ioprio(struct task_struct *p)
 160 {
 161         int ret;
 162
 163         ret = security_task_getioprio(p);
 164         if (ret)
 165                 goto out;
 166         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 167         task_lock(p);
 168         if (p->io_context)
 169                 ret = p->io_context->ioprio;
 170         task_unlock(p);
 171 out:
 172         return ret;
 173 }
 174
 175 int ioprio_best(unsigned short aprio, unsigned short bprio)
 176 {
 177         if (!ioprio_valid(aprio))
 178                 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 179         if (!ioprio_valid(bprio))
 180                 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 181
 182         return min(aprio, bprio);
 183 }
 184
 185 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 186 {
 187         struct task_struct *g, *p;
 188         struct user_struct *user;
 189         struct pid *pgrp;
 190         kuid_t uid;
 191         int ret = -ESRCH;
 192         int tmpio;
 193
 194         rcu_read_lock();
 195         switch (which) {
 196                 case IOPRIO_WHO_PROCESS:
 197                         if (!who)
 198                                 p = current;
 199                         else
 200                                 p = find_task_by_vpid(who);
 201                         if (p)
 202                                 ret = get_task_ioprio(p);
 203                         break;
 204                 case IOPRIO_WHO_PGRP:
 205                         if (!who)
 206                                 pgrp = task_pgrp(current);
 207                         else
 208                                 pgrp = find_vpid(who);
 209                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 210                                 tmpio = get_task_ioprio(p);
 211                                 if (tmpio < 0)
 212                                         continue;
 213                                 if (ret == -ESRCH)
 214                                         ret = tmpio;
 215                                 else
 216                                         ret = ioprio_best(ret, tmpio);
 217                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 218                         break;
 219                 case IOPRIO_WHO_USER:
 220                         uid = make_kuid(current_user_ns(), who);
 221                         if (!who)
 222                                 user = current_user();
 223                         else
 224                                 user = find_user(uid);
 225
 226                         if (!user)
 227                                 break;
 228
 229                         for_each_process_thread(g, p) {
 230                                 if (!uid_eq(task_uid(p), user->uid) ||
 231                                     !task_pid_vnr(p))
 232                                         continue;
 233                                 tmpio = get_task_ioprio(p);
 234                                 if (tmpio < 0)
 235                                         continue;
 236                                 if (ret == -ESRCH)
 237                                         ret = tmpio;
 238                                 else
 239                                         ret = ioprio_best(ret, tmpio);
 240                         }
 241
 242                         if (who)
 243                                 free_uid(user);
 244                         break;
 245                 default:
 246                         ret = -EINVAL;
 247         }
 248
 249         rcu_read_unlock();
 250         return ret;
 251 }