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![Arnd Bergmann](/assets/img/avatar_default.png)
These two drivers use identical code for their procfs status file handling, which contains a small race against status data becoming available while reading the file. This uses wait_event_interruptible instead to fix this particular race and eventually get rid of all sleep_on instances. There seems to be another race involving multiple concurrent readers of the same procfs file, which I don't try to fix here. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Karsten Keil <isdn@linux-pingi.de> Cc: netdev@vger.kernel.org Signed-off-by: David S. Miller <davem@davemloft.net>
336 lines
8.8 KiB
C
336 lines
8.8 KiB
C
/* $Id: divert_procfs.c,v 1.11.6.2 2001/09/23 22:24:36 kai Exp $
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*
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* Filesystem handling for the diversion supplementary services.
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*
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* Copyright 1998 by Werner Cornelius (werner@isdn4linux.de)
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*
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* This software may be used and distributed according to the terms
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* of the GNU General Public License, incorporated herein by reference.
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*
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*/
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#include <linux/module.h>
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#include <linux/poll.h>
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#include <linux/slab.h>
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#ifdef CONFIG_PROC_FS
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#include <linux/proc_fs.h>
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#else
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#include <linux/fs.h>
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#endif
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#include <linux/sched.h>
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#include <linux/isdnif.h>
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#include <net/net_namespace.h>
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#include <linux/mutex.h>
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#include "isdn_divert.h"
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/*********************************/
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/* Variables for interface queue */
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/*********************************/
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ulong if_used = 0; /* number of interface users */
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static DEFINE_MUTEX(isdn_divert_mutex);
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static struct divert_info *divert_info_head = NULL; /* head of queue */
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static struct divert_info *divert_info_tail = NULL; /* pointer to last entry */
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static DEFINE_SPINLOCK(divert_info_lock);/* lock for queue */
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static wait_queue_head_t rd_queue;
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/*********************************/
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/* put an info buffer into queue */
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/*********************************/
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void
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put_info_buffer(char *cp)
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{
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struct divert_info *ib;
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unsigned long flags;
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if (if_used <= 0)
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return;
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if (!cp)
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return;
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if (!*cp)
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return;
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if (!(ib = kmalloc(sizeof(struct divert_info) + strlen(cp), GFP_ATOMIC)))
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return; /* no memory */
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strcpy(ib->info_start, cp); /* set output string */
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ib->next = NULL;
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spin_lock_irqsave(&divert_info_lock, flags);
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ib->usage_cnt = if_used;
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if (!divert_info_head)
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divert_info_head = ib; /* new head */
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else
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divert_info_tail->next = ib; /* follows existing messages */
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divert_info_tail = ib; /* new tail */
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/* delete old entrys */
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while (divert_info_head->next) {
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if ((divert_info_head->usage_cnt <= 0) &&
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(divert_info_head->next->usage_cnt <= 0)) {
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ib = divert_info_head;
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divert_info_head = divert_info_head->next;
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kfree(ib);
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} else
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break;
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} /* divert_info_head->next */
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spin_unlock_irqrestore(&divert_info_lock, flags);
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wake_up_interruptible(&(rd_queue));
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} /* put_info_buffer */
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#ifdef CONFIG_PROC_FS
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/**********************************/
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/* deflection device read routine */
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/**********************************/
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static ssize_t
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isdn_divert_read(struct file *file, char __user *buf, size_t count, loff_t *off)
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{
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struct divert_info *inf;
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int len;
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if (!(inf = *((struct divert_info **) file->private_data))) {
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if (file->f_flags & O_NONBLOCK)
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return -EAGAIN;
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wait_event_interruptible(rd_queue, (inf =
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*((struct divert_info **) file->private_data)));
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}
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if (!inf)
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return (0);
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inf->usage_cnt--; /* new usage count */
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file->private_data = &inf->next; /* next structure */
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if ((len = strlen(inf->info_start)) <= count) {
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if (copy_to_user(buf, inf->info_start, len))
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return -EFAULT;
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*off += len;
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return (len);
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}
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return (0);
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} /* isdn_divert_read */
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/**********************************/
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/* deflection device write routine */
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/**********************************/
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static ssize_t
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isdn_divert_write(struct file *file, const char __user *buf, size_t count, loff_t *off)
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{
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return (-ENODEV);
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} /* isdn_divert_write */
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/***************************************/
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/* select routines for various kernels */
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/***************************************/
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static unsigned int
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isdn_divert_poll(struct file *file, poll_table *wait)
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{
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unsigned int mask = 0;
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poll_wait(file, &(rd_queue), wait);
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/* mask = POLLOUT | POLLWRNORM; */
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if (*((struct divert_info **) file->private_data)) {
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mask |= POLLIN | POLLRDNORM;
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}
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return mask;
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} /* isdn_divert_poll */
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/****************/
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/* Open routine */
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/****************/
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static int
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isdn_divert_open(struct inode *ino, struct file *filep)
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{
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unsigned long flags;
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spin_lock_irqsave(&divert_info_lock, flags);
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if_used++;
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if (divert_info_head)
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filep->private_data = &(divert_info_tail->next);
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else
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filep->private_data = &divert_info_head;
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spin_unlock_irqrestore(&divert_info_lock, flags);
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/* start_divert(); */
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return nonseekable_open(ino, filep);
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} /* isdn_divert_open */
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/*******************/
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/* close routine */
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/*******************/
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static int
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isdn_divert_close(struct inode *ino, struct file *filep)
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{
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struct divert_info *inf;
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unsigned long flags;
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spin_lock_irqsave(&divert_info_lock, flags);
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if_used--;
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inf = *((struct divert_info **) filep->private_data);
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while (inf) {
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inf->usage_cnt--;
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inf = inf->next;
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}
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if (if_used <= 0)
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while (divert_info_head) {
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inf = divert_info_head;
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divert_info_head = divert_info_head->next;
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kfree(inf);
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}
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spin_unlock_irqrestore(&divert_info_lock, flags);
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return (0);
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} /* isdn_divert_close */
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/*********/
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/* IOCTL */
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/*********/
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static int isdn_divert_ioctl_unlocked(struct file *file, uint cmd, ulong arg)
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{
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divert_ioctl dioctl;
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int i;
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unsigned long flags;
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divert_rule *rulep;
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char *cp;
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if (copy_from_user(&dioctl, (void __user *) arg, sizeof(dioctl)))
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return -EFAULT;
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switch (cmd) {
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case IIOCGETVER:
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dioctl.drv_version = DIVERT_IIOC_VERSION; /* set version */
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break;
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case IIOCGETDRV:
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if ((dioctl.getid.drvid = divert_if.name_to_drv(dioctl.getid.drvnam)) < 0)
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return (-EINVAL);
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break;
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case IIOCGETNAM:
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cp = divert_if.drv_to_name(dioctl.getid.drvid);
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if (!cp)
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return (-EINVAL);
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if (!*cp)
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return (-EINVAL);
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strcpy(dioctl.getid.drvnam, cp);
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break;
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case IIOCGETRULE:
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if (!(rulep = getruleptr(dioctl.getsetrule.ruleidx)))
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return (-EINVAL);
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dioctl.getsetrule.rule = *rulep; /* copy data */
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break;
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case IIOCMODRULE:
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if (!(rulep = getruleptr(dioctl.getsetrule.ruleidx)))
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return (-EINVAL);
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spin_lock_irqsave(&divert_lock, flags);
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*rulep = dioctl.getsetrule.rule; /* copy data */
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spin_unlock_irqrestore(&divert_lock, flags);
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return (0); /* no copy required */
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break;
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case IIOCINSRULE:
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return (insertrule(dioctl.getsetrule.ruleidx, &dioctl.getsetrule.rule));
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break;
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case IIOCDELRULE:
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return (deleterule(dioctl.getsetrule.ruleidx));
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break;
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case IIOCDODFACT:
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return (deflect_extern_action(dioctl.fwd_ctrl.subcmd,
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dioctl.fwd_ctrl.callid,
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dioctl.fwd_ctrl.to_nr));
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case IIOCDOCFACT:
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case IIOCDOCFDIS:
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case IIOCDOCFINT:
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if (!divert_if.drv_to_name(dioctl.cf_ctrl.drvid))
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return (-EINVAL); /* invalid driver */
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if (strnlen(dioctl.cf_ctrl.msn, sizeof(dioctl.cf_ctrl.msn)) ==
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sizeof(dioctl.cf_ctrl.msn))
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return -EINVAL;
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if (strnlen(dioctl.cf_ctrl.fwd_nr, sizeof(dioctl.cf_ctrl.fwd_nr)) ==
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sizeof(dioctl.cf_ctrl.fwd_nr))
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return -EINVAL;
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if ((i = cf_command(dioctl.cf_ctrl.drvid,
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(cmd == IIOCDOCFACT) ? 1 : (cmd == IIOCDOCFDIS) ? 0 : 2,
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dioctl.cf_ctrl.cfproc,
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dioctl.cf_ctrl.msn,
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dioctl.cf_ctrl.service,
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dioctl.cf_ctrl.fwd_nr,
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&dioctl.cf_ctrl.procid)))
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return (i);
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break;
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default:
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return (-EINVAL);
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} /* switch cmd */
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return copy_to_user((void __user *)arg, &dioctl, sizeof(dioctl)) ? -EFAULT : 0;
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} /* isdn_divert_ioctl */
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static long isdn_divert_ioctl(struct file *file, uint cmd, ulong arg)
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{
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long ret;
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mutex_lock(&isdn_divert_mutex);
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ret = isdn_divert_ioctl_unlocked(file, cmd, arg);
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mutex_unlock(&isdn_divert_mutex);
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return ret;
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}
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static const struct file_operations isdn_fops =
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{
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.owner = THIS_MODULE,
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.llseek = no_llseek,
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.read = isdn_divert_read,
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.write = isdn_divert_write,
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.poll = isdn_divert_poll,
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.unlocked_ioctl = isdn_divert_ioctl,
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.open = isdn_divert_open,
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.release = isdn_divert_close,
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};
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/****************************/
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/* isdn subdir in /proc/net */
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/****************************/
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static struct proc_dir_entry *isdn_proc_entry = NULL;
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static struct proc_dir_entry *isdn_divert_entry = NULL;
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#endif /* CONFIG_PROC_FS */
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/***************************************************************************/
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/* divert_dev_init must be called before the proc filesystem may be used */
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/***************************************************************************/
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int
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divert_dev_init(void)
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{
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init_waitqueue_head(&rd_queue);
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#ifdef CONFIG_PROC_FS
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isdn_proc_entry = proc_mkdir("isdn", init_net.proc_net);
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if (!isdn_proc_entry)
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return (-1);
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isdn_divert_entry = proc_create("divert", S_IFREG | S_IRUGO,
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isdn_proc_entry, &isdn_fops);
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if (!isdn_divert_entry) {
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remove_proc_entry("isdn", init_net.proc_net);
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return (-1);
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}
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#endif /* CONFIG_PROC_FS */
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return (0);
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} /* divert_dev_init */
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/***************************************************************************/
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/* divert_dev_deinit must be called before leaving isdn when included as */
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/* a module. */
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/***************************************************************************/
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int
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divert_dev_deinit(void)
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{
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#ifdef CONFIG_PROC_FS
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remove_proc_entry("divert", isdn_proc_entry);
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remove_proc_entry("isdn", init_net.proc_net);
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#endif /* CONFIG_PROC_FS */
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return (0);
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} /* divert_dev_deinit */
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