fs/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 (tcred->uid != cred->euid &&
  41             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                 ioc->ioprio_changed = 1;
  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         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                         if (!who)
 115                                 user = current_user();
 116                         else
 117                                 user = find_user(who);
 118
 119                         if (!user)
 120                                 break;
 121
 122                         do_each_thread(g, p) {
 123                                 if (__task_cred(p)->uid != who)
 124                                         continue;
 125                                 ret = set_task_ioprio(p, ioprio);
 126                                 if (ret)
 127                                         goto free_uid;
 128                         } while_each_thread(g, p);
 129 free_uid:
 130                         if (who)
 131                                 free_uid(user);
 132                         break;
 133                 default:
 134                         ret = -EINVAL;
 135         }
 136
 137         rcu_read_unlock();
 138         return ret;
 139 }
 140
 141 static int get_task_ioprio(struct task_struct *p)
 142 {
 143         int ret;
 144
 145         ret = security_task_getioprio(p);
 146         if (ret)
 147                 goto out;
 148         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 149         if (p->io_context)
 150                 ret = p->io_context->ioprio;
 151 out:
 152         return ret;
 153 }
 154
 155 int ioprio_best(unsigned short aprio, unsigned short bprio)
 156 {
 157         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
 158         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
 159
 160         if (aclass == IOPRIO_CLASS_NONE)
 161                 aclass = IOPRIO_CLASS_BE;
 162         if (bclass == IOPRIO_CLASS_NONE)
 163                 bclass = IOPRIO_CLASS_BE;
 164
 165         if (aclass == bclass)
 166                 return min(aprio, bprio);
 167         if (aclass > bclass)
 168                 return bprio;
 169         else
 170                 return aprio;
 171 }
 172
 173 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 174 {
 175         struct task_struct *g, *p;
 176         struct user_struct *user;
 177         struct pid *pgrp;
 178         int ret = -ESRCH;
 179         int tmpio;
 180
 181         rcu_read_lock();
 182         switch (which) {
 183                 case IOPRIO_WHO_PROCESS:
 184                         if (!who)
 185                                 p = current;
 186                         else
 187                                 p = find_task_by_vpid(who);
 188                         if (p)
 189                                 ret = get_task_ioprio(p);
 190                         break;
 191                 case IOPRIO_WHO_PGRP:
 192                         if (!who)
 193                                 pgrp = task_pgrp(current);
 194                         else
 195                                 pgrp = find_vpid(who);
 196                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 197                                 tmpio = get_task_ioprio(p);
 198                                 if (tmpio < 0)
 199                                         continue;
 200                                 if (ret == -ESRCH)
 201                                         ret = tmpio;
 202                                 else
 203                                         ret = ioprio_best(ret, tmpio);
 204                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 205                         break;
 206                 case IOPRIO_WHO_USER:
 207                         if (!who)
 208                                 user = current_user();
 209                         else
 210                                 user = find_user(who);
 211
 212                         if (!user)
 213                                 break;
 214
 215                         do_each_thread(g, p) {
 216                                 if (__task_cred(p)->uid != user->uid)
 217                                         continue;
 218                                 tmpio = get_task_ioprio(p);
 219                                 if (tmpio < 0)
 220                                         continue;
 221                                 if (ret == -ESRCH)
 222                                         ret = tmpio;
 223                                 else
 224                                         ret = ioprio_best(ret, tmpio);
 225                         } while_each_thread(g, p);
 226
 227                         if (who)
 228                                 free_uid(user);
 229                         break;
 230                 default:
 231                         ret = -EINVAL;
 232         }
 233
 234         rcu_read_unlock();
 235         return ret;
 236 }