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TOMOYO Linux Cross Reference
Linux/fs/ioprio.c

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  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/kernel.h>
 23 #include <linux/ioprio.h>
 24 #include <linux/blkdev.h>
 25 #include <linux/capability.h>
 26 #include <linux/syscalls.h>
 27 #include <linux/security.h>
 28 #include <linux/pid_namespace.h>
 29 
 30 int set_task_ioprio(struct task_struct *task, int ioprio)
 31 {
 32         int err;
 33         struct io_context *ioc;
 34         const struct cred *cred = current_cred(), *tcred;
 35 
 36         rcu_read_lock();
 37         tcred = __task_cred(task);
 38         if (tcred->uid != cred->euid &&
 39             tcred->uid != cred->uid && !capable(CAP_SYS_NICE)) {
 40                 rcu_read_unlock();
 41                 return -EPERM;
 42         }
 43         rcu_read_unlock();
 44 
 45         err = security_task_setioprio(task, ioprio);
 46         if (err)
 47                 return err;
 48 
 49         task_lock(task);
 50         do {
 51                 ioc = task->io_context;
 52                 /* see wmb() in current_io_context() */
 53                 smp_read_barrier_depends();
 54                 if (ioc)
 55                         break;
 56 
 57                 ioc = alloc_io_context(GFP_ATOMIC, -1);
 58                 if (!ioc) {
 59                         err = -ENOMEM;
 60                         break;
 61                 }
 62                 task->io_context = ioc;
 63         } while (1);
 64 
 65         if (!err) {
 66                 ioc->ioprio = ioprio;
 67                 ioc->ioprio_changed = 1;
 68         }
 69 
 70         task_unlock(task);
 71         return err;
 72 }
 73 EXPORT_SYMBOL_GPL(set_task_ioprio);
 74 
 75 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
 76 {
 77         int class = IOPRIO_PRIO_CLASS(ioprio);
 78         int data = IOPRIO_PRIO_DATA(ioprio);
 79         struct task_struct *p, *g;
 80         struct user_struct *user;
 81         struct pid *pgrp;
 82         int ret;
 83 
 84         switch (class) {
 85                 case IOPRIO_CLASS_RT:
 86                         if (!capable(CAP_SYS_ADMIN))
 87                                 return -EPERM;
 88                         /* fall through, rt has prio field too */
 89                 case IOPRIO_CLASS_BE:
 90                         if (data >= IOPRIO_BE_NR || data < 0)
 91                                 return -EINVAL;
 92 
 93                         break;
 94                 case IOPRIO_CLASS_IDLE:
 95                         break;
 96                 case IOPRIO_CLASS_NONE:
 97                         if (data)
 98                                 return -EINVAL;
 99                         break;
100                 default:
101                         return -EINVAL;
102         }
103 
104         ret = -ESRCH;
105         /*
106          * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic",
107          * so we can't use rcu_read_lock(). See re-copy of ->ioprio
108          * in copy_process().
109          */
110         read_lock(&tasklist_lock);
111         switch (which) {
112                 case IOPRIO_WHO_PROCESS:
113                         if (!who)
114                                 p = current;
115                         else
116                                 p = find_task_by_vpid(who);
117                         if (p)
118                                 ret = set_task_ioprio(p, ioprio);
119                         break;
120                 case IOPRIO_WHO_PGRP:
121                         if (!who)
122                                 pgrp = task_pgrp(current);
123                         else
124                                 pgrp = find_vpid(who);
125                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
126                                 ret = set_task_ioprio(p, ioprio);
127                                 if (ret)
128                                         break;
129                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
130                         break;
131                 case IOPRIO_WHO_USER:
132                         if (!who)
133                                 user = current_user();
134                         else
135                                 user = find_user(who);
136 
137                         if (!user)
138                                 break;
139 
140                         do_each_thread(g, p) {
141                                 if (__task_cred(p)->uid != who)
142                                         continue;
143                                 ret = set_task_ioprio(p, ioprio);
144                                 if (ret)
145                                         goto free_uid;
146                         } while_each_thread(g, p);
147 free_uid:
148                         if (who)
149                                 free_uid(user);
150                         break;
151                 default:
152                         ret = -EINVAL;
153         }
154 
155         read_unlock(&tasklist_lock);
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         if (p->io_context)
168                 ret = p->io_context->ioprio;
169 out:
170         return ret;
171 }
172 
173 int ioprio_best(unsigned short aprio, unsigned short bprio)
174 {
175         unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
176         unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
177 
178         if (aclass == IOPRIO_CLASS_NONE)
179                 aclass = IOPRIO_CLASS_BE;
180         if (bclass == IOPRIO_CLASS_NONE)
181                 bclass = IOPRIO_CLASS_BE;
182 
183         if (aclass == bclass)
184                 return min(aprio, bprio);
185         if (aclass > bclass)
186                 return bprio;
187         else
188                 return aprio;
189 }
190 
191 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
192 {
193         struct task_struct *g, *p;
194         struct user_struct *user;
195         struct pid *pgrp;
196         int ret = -ESRCH;
197         int tmpio;
198 
199         read_lock(&tasklist_lock);
200         switch (which) {
201                 case IOPRIO_WHO_PROCESS:
202                         if (!who)
203                                 p = current;
204                         else
205                                 p = find_task_by_vpid(who);
206                         if (p)
207                                 ret = get_task_ioprio(p);
208                         break;
209                 case IOPRIO_WHO_PGRP:
210                         if (!who)
211                                 pgrp = task_pgrp(current);
212                         else
213                                 pgrp = find_vpid(who);
214                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
215                                 tmpio = get_task_ioprio(p);
216                                 if (tmpio < 0)
217                                         continue;
218                                 if (ret == -ESRCH)
219                                         ret = tmpio;
220                                 else
221                                         ret = ioprio_best(ret, tmpio);
222                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
223                         break;
224                 case IOPRIO_WHO_USER:
225                         if (!who)
226                                 user = current_user();
227                         else
228                                 user = find_user(who);
229 
230                         if (!user)
231                                 break;
232 
233                         do_each_thread(g, p) {
234                                 if (__task_cred(p)->uid != user->uid)
235                                         continue;
236                                 tmpio = get_task_ioprio(p);
237                                 if (tmpio < 0)
238                                         continue;
239                                 if (ret == -ESRCH)
240                                         ret = tmpio;
241                                 else
242                                         ret = ioprio_best(ret, tmpio);
243                         } while_each_thread(g, p);
244 
245                         if (who)
246                                 free_uid(user);
247                         break;
248                 default:
249                         ret = -EINVAL;
250         }
251 
252         read_unlock(&tasklist_lock);
253         return ret;
254 }
255 

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