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 */
  79                         /* rt has prio field too */
  80                 case IOPRIO_CLASS_BE:
  81                         if (data >= IOPRIO_BE_NR || data < 0)
  82                                 return -EINVAL;
  83
  84                         break;
  85                 case IOPRIO_CLASS_IDLE:
  86                         break;
  87                 case IOPRIO_CLASS_NONE:
  88                         if (data)
  89                                 return -EINVAL;
  90                         break;
  91                 default:
  92                         return -EINVAL;
  93         }
  94
  95         ret = -ESRCH;
  96         rcu_read_lock();
  97         switch (which) {
  98                 case IOPRIO_WHO_PROCESS:
  99                         if (!who)
 100                                 p = current;
 101                         else
 102                                 p = find_task_by_vpid(who);
 103                         if (p)
 104                                 ret = set_task_ioprio(p, ioprio);
 105                         break;
 106                 case IOPRIO_WHO_PGRP:
 107                         if (!who)
 108                                 pgrp = task_pgrp(current);
 109                         else
 110                                 pgrp = find_vpid(who);
 111                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 112                                 ret = set_task_ioprio(p, ioprio);
 113                                 if (ret)
 114                                         break;
 115                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 116                         break;
 117                 case IOPRIO_WHO_USER:
 118                         uid = make_kuid(current_user_ns(), who);
 119                         if (!uid_valid(uid))
 120                                 break;
 121                         if (!who)
 122                                 user = current_user();
 123                         else
 124                                 user = find_user(uid);
 125
 126                         if (!user)
 127                                 break;
 128
 129                         for_each_process_thread(g, p) {
 130                                 if (!uid_eq(task_uid(p), uid) ||
 131                                     !task_pid_vnr(p))
 132                                         continue;
 133                                 ret = set_task_ioprio(p, ioprio);
 134                                 if (ret)
 135                                         goto free_uid;
 136                         }
 137 free_uid:
 138                         if (who)
 139                                 free_uid(user);
 140                         break;
 141                 default:
 142                         ret = -EINVAL;
 143         }
 144
 145         rcu_read_unlock();
 146         return ret;
 147 }
 148
 149 static int get_task_ioprio(struct task_struct *p)
 150 {
 151         int ret;
 152
 153         ret = security_task_getioprio(p);
 154         if (ret)
 155                 goto out;
 156         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 157         task_lock(p);
 158         if (p->io_context)
 159                 ret = p->io_context->ioprio;
 160         task_unlock(p);
 161 out:
 162         return ret;
 163 }
 164
 165 int ioprio_best(unsigned short aprio, unsigned short bprio)
 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         return min(aprio, bprio);
 173 }
 174
 175 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 176 {
 177         struct task_struct *g, *p;
 178         struct user_struct *user;
 179         struct pid *pgrp;
 180         kuid_t uid;
 181         int ret = -ESRCH;
 182         int tmpio;
 183
 184         rcu_read_lock();
 185         switch (which) {
 186                 case IOPRIO_WHO_PROCESS:
 187                         if (!who)
 188                                 p = current;
 189                         else
 190                                 p = find_task_by_vpid(who);
 191                         if (p)
 192                                 ret = get_task_ioprio(p);
 193                         break;
 194                 case IOPRIO_WHO_PGRP:
 195                         if (!who)
 196                                 pgrp = task_pgrp(current);
 197                         else
 198                                 pgrp = find_vpid(who);
 199                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 200                                 tmpio = get_task_ioprio(p);
 201                                 if (tmpio < 0)
 202                                         continue;
 203                                 if (ret == -ESRCH)
 204                                         ret = tmpio;
 205                                 else
 206                                         ret = ioprio_best(ret, tmpio);
 207                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 208                         break;
 209                 case IOPRIO_WHO_USER:
 210                         uid = make_kuid(current_user_ns(), who);
 211                         if (!who)
 212                                 user = current_user();
 213                         else
 214                                 user = find_user(uid);
 215
 216                         if (!user)
 217                                 break;
 218
 219                         for_each_process_thread(g, p) {
 220                                 if (!uid_eq(task_uid(p), user->uid) ||
 221                                     !task_pid_vnr(p))
 222                                         continue;
 223                                 tmpio = get_task_ioprio(p);
 224                                 if (tmpio < 0)
 225                                         continue;
 226                                 if (ret == -ESRCH)
 227                                         ret = tmpio;
 228                                 else
 229                                         ret = ioprio_best(ret, tmpio);
 230                         }
 231
 232                         if (who)
 233                                 free_uid(user);
 234                         break;
 235                 default:
 236                         ret = -EINVAL;
 237         }
 238
 239         rcu_read_unlock();
 240         return ret;
 241 }