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/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 (!uid_eq(tcred->uid, cred->euid) &&
  41             !uid_eq(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 = ioprio;
  54                 put_io_context(ioc);
  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         kuid_t uid;
  69         int ret;
  70
  71         switch (class) {
  72                 case IOPRIO_CLASS_RT:
  73                         if (!capable(CAP_SYS_ADMIN))
  74                                 return -EPERM;
  75                         /* fall through, rt has prio field too */
  76                 case IOPRIO_CLASS_BE:
  77                         if (data >= IOPRIO_BE_NR || data < 0)
  78                                 return -EINVAL;
  79
  80                         break;
  81                 case IOPRIO_CLASS_IDLE:
  82                         break;
  83                 case IOPRIO_CLASS_NONE:
  84                         if (data)
  85                                 return -EINVAL;
  86                         break;
  87                 default:
  88                         return -EINVAL;
  89         }
  90
  91         ret = -ESRCH;
  92         rcu_read_lock();
  93         switch (which) {
  94                 case IOPRIO_WHO_PROCESS:
  95                         if (!who)
  96                                 p = current;
  97                         else
  98                                 p = find_task_by_vpid(who);
  99                         if (p)
 100                                 ret = set_task_ioprio(p, ioprio);
 101                         break;
 102                 case IOPRIO_WHO_PGRP:
 103                         if (!who)
 104                                 pgrp = task_pgrp(current);
 105                         else
 106                                 pgrp = find_vpid(who);
 107                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 108                                 ret = set_task_ioprio(p, ioprio);
 109                                 if (ret)
 110                                         break;
 111                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 112                         break;
 113                 case IOPRIO_WHO_USER:
 114                         uid = make_kuid(current_user_ns(), who);
 115                         if (!uid_valid(uid))
 116                                 break;
 117                         if (!who)
 118                                 user = current_user();
 119                         else
 120                                 user = find_user(uid);
 121
 122                         if (!user)
 123                                 break;
 124
 125                         do_each_thread(g, p) {
 126                                 if (!uid_eq(task_uid(p), uid) ||
 127                                     !task_pid_vnr(p))
 128                                         continue;
 129                                 ret = set_task_ioprio(p, ioprio);
 130                                 if (ret)
 131                                         goto free_uid;
 132                         } while_each_thread(g, p);
 133 free_uid:
 134                         if (who)
 135                                 free_uid(user);
 136                         break;
 137                 default:
 138                         ret = -EINVAL;
 139         }
 140
 141         rcu_read_unlock();
 142         return ret;
 143 }
 144
 145 static int get_task_ioprio(struct task_struct *p)
 146 {
 147         int ret;
 148
 149         ret = security_task_getioprio(p);
 150         if (ret)
 151                 goto out;
 152         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 153         if (p->io_context)
 154                 ret = p->io_context->ioprio;
 155 out:
 156         return ret;
 157 }
 158
 159 int ioprio_best(unsigned short aprio, unsigned short bprio)
 160 {
 161         unsigned short aclass;
 162         unsigned short bclass;
 163
 164         if (!ioprio_valid(aprio))
 165                 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 166         if (!ioprio_valid(bprio))
 167                 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 168
 169         aclass = IOPRIO_PRIO_CLASS(aprio);
 170         bclass = IOPRIO_PRIO_CLASS(bprio);
 171         if (aclass == bclass)
 172                 return min(aprio, bprio);
 173         if (aclass > bclass)
 174                 return bprio;
 175         else
 176                 return aprio;
 177 }
 178
 179 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 180 {
 181         struct task_struct *g, *p;
 182         struct user_struct *user;
 183         struct pid *pgrp;
 184         kuid_t uid;
 185         int ret = -ESRCH;
 186         int tmpio;
 187
 188         rcu_read_lock();
 189         switch (which) {
 190                 case IOPRIO_WHO_PROCESS:
 191                         if (!who)
 192                                 p = current;
 193                         else
 194                                 p = find_task_by_vpid(who);
 195                         if (p)
 196                                 ret = get_task_ioprio(p);
 197                         break;
 198                 case IOPRIO_WHO_PGRP:
 199                         if (!who)
 200                                 pgrp = task_pgrp(current);
 201                         else
 202                                 pgrp = find_vpid(who);
 203                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 204                                 tmpio = get_task_ioprio(p);
 205                                 if (tmpio < 0)
 206                                         continue;
 207                                 if (ret == -ESRCH)
 208                                         ret = tmpio;
 209                                 else
 210                                         ret = ioprio_best(ret, tmpio);
 211                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 212                         break;
 213                 case IOPRIO_WHO_USER:
 214                         uid = make_kuid(current_user_ns(), who);
 215                         if (!who)
 216                                 user = current_user();
 217                         else
 218                                 user = find_user(uid);
 219
 220                         if (!user)
 221                                 break;
 222
 223                         do_each_thread(g, p) {
 224                                 if (!uid_eq(task_uid(p), user->uid) ||
 225                                     !task_pid_vnr(p))
 226                                         continue;
 227                                 tmpio = get_task_ioprio(p);
 228                                 if (tmpio < 0)
 229                                         continue;
 230                                 if (ret == -ESRCH)
 231                                         ret = tmpio;
 232                                 else
 233                                         ret = ioprio_best(ret, tmpio);
 234                         } while_each_thread(g, p);
 235
 236                         if (who)
 237                                 free_uid(user);
 238                         break;
 239                 default:
 240                         ret = -EINVAL;
 241         }
 242
 243         rcu_read_unlock();
 244         return ret;
 245 }