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Linux/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         task_lock(p);
154         if (p->io_context)
155                 ret = p->io_context->ioprio;
156         task_unlock(p);
157 out:
158         return ret;
159 }
160 
161 int ioprio_best(unsigned short aprio, unsigned short bprio)
162 {
163         unsigned short aclass;
164         unsigned short bclass;
165 
166         if (!ioprio_valid(aprio))
167                 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
168         if (!ioprio_valid(bprio))
169                 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
170 
171         aclass = IOPRIO_PRIO_CLASS(aprio);
172         bclass = IOPRIO_PRIO_CLASS(bprio);
173         if (aclass == bclass)
174                 return min(aprio, bprio);
175         if (aclass > bclass)
176                 return bprio;
177         else
178                 return aprio;
179 }
180 
181 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
182 {
183         struct task_struct *g, *p;
184         struct user_struct *user;
185         struct pid *pgrp;
186         kuid_t uid;
187         int ret = -ESRCH;
188         int tmpio;
189 
190         rcu_read_lock();
191         switch (which) {
192                 case IOPRIO_WHO_PROCESS:
193                         if (!who)
194                                 p = current;
195                         else
196                                 p = find_task_by_vpid(who);
197                         if (p)
198                                 ret = get_task_ioprio(p);
199                         break;
200                 case IOPRIO_WHO_PGRP:
201                         if (!who)
202                                 pgrp = task_pgrp(current);
203                         else
204                                 pgrp = find_vpid(who);
205                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
206                                 tmpio = get_task_ioprio(p);
207                                 if (tmpio < 0)
208                                         continue;
209                                 if (ret == -ESRCH)
210                                         ret = tmpio;
211                                 else
212                                         ret = ioprio_best(ret, tmpio);
213                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
214                         break;
215                 case IOPRIO_WHO_USER:
216                         uid = make_kuid(current_user_ns(), who);
217                         if (!who)
218                                 user = current_user();
219                         else
220                                 user = find_user(uid);
221 
222                         if (!user)
223                                 break;
224 
225                         do_each_thread(g, p) {
226                                 if (!uid_eq(task_uid(p), user->uid) ||
227                                     !task_pid_vnr(p))
228                                         continue;
229                                 tmpio = get_task_ioprio(p);
230                                 if (tmpio < 0)
231                                         continue;
232                                 if (ret == -ESRCH)
233                                         ret = tmpio;
234                                 else
235                                         ret = ioprio_best(ret, tmpio);
236                         } while_each_thread(g, p);
237 
238                         if (who)
239                                 free_uid(user);
240                         break;
241                 default:
242                         ret = -EINVAL;
243         }
244 
245         rcu_read_unlock();
246         return ret;
247 }
248 

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