/* -*- linux-c -*- --------------------------------------------------------- *
   *
   * linux/fs/autofs/waitq.c
   *
   *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
   *
   * This file is part of the Linux kernel and is made available under
   * the terms of the GNU General Public License, version 2, or at your
   * option, any later version, incorporated herein by reference.
   *
   * ------------------------------------------------------------------------- */
  
  #include <linux/slab.h>
  #include <linux/time.h>
  #include <linux/signal.h>
  #include <linux/file.h>
  #include "autofs_i.h"
  
  /* We make this a static variable rather than a part of the superblock; it
     is better if we don't reassign numbers easily even across filesystems */
  static autofs_wqt_t autofs_next_wait_queue = 1;
  
  /* These are the signals we allow interrupting a pending mount */
  #define SHUTDOWN_SIGS	(sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
  
  void autofs_catatonic_mode(struct autofs_sb_info *sbi)
  {
  	struct autofs_wait_queue *wq, *nwq;
  
  	DPRINTK(("autofs: entering catatonic mode
  "));
  
  	sbi->catatonic = 1;
  	wq = sbi->queues;
  	sbi->queues = NULL;	/* Erase all wait queues */
  	while ( wq ) {
  		nwq = wq->next;
  		wq->status = -ENOENT; /* Magic is gone - report failure */
  		kfree(wq->name);
  		wq->name = NULL;
  		wake_up(&wq->queue);
  		wq = nwq;
  	}
  	fput(sbi->pipe);	/* Close the pipe */

  	sbi->pipe = NULL;

  	autofs_hash_dputall(&sbi->dirhash); /* Remove all dentry pointers */
  }
  
  static int autofs_write(struct file *file, const void *addr, int bytes)
  {
  	unsigned long sigpipe, flags;
  	mm_segment_t fs;
  	const char *data = (const char *)addr;
  	ssize_t wr = 0;
  
  	/** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
  
  	sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  
  	/* Save pointer to user space and point back to kernel space */
  	fs = get_fs();
  	set_fs(KERNEL_DS);
  
  	while (bytes &&
  	       (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  		data += wr;
  		bytes -= wr;
  	}
  
  	set_fs(fs);
  
  	/* Keep the currently executing process from receiving a
  	   SIGPIPE unless it was already supposed to get one */
  	if (wr == -EPIPE && !sigpipe) {
  		spin_lock_irqsave(&current->sighand->siglock, flags);
  		sigdelset(&current->pending.signal, SIGPIPE);
  		recalc_sigpending();
  		spin_unlock_irqrestore(&current->sighand->siglock, flags);
  	}
  
  	return (bytes > 0);
  }
  	
  static void autofs_notify_daemon(struct autofs_sb_info *sbi, struct autofs_wait_queue *wq)
  {
  	struct autofs_packet_missing pkt;
  
  	DPRINTK(("autofs_wait: wait id = 0x%08lx, name = ", wq->wait_queue_token));
  	autofs_say(wq->name,wq->len);
  
  	memset(&pkt,0,sizeof pkt); /* For security reasons */
  
  	pkt.hdr.proto_version = AUTOFS_PROTO_VERSION;
  	pkt.hdr.type = autofs_ptype_missing;
  	pkt.wait_queue_token = wq->wait_queue_token;
  	pkt.len = wq->len;
          memcpy(pkt.name, wq->name, pkt.len);
  	pkt.name[pkt.len] = '\0';
  
  	if ( autofs_write(sbi->pipe,&pkt,sizeof(struct autofs_packet_missing)) )
  		autofs_catatonic_mode(sbi);
  }
  
  int autofs_wait(struct autofs_sb_info *sbi, struct qstr *name)
  {
  	struct autofs_wait_queue *wq;
  	int status;
  
  	/* In catatonic mode, we don't wait for nobody */
  	if ( sbi->catatonic )
  		return -ENOENT;
  	
  	/* We shouldn't be able to get here, but just in case */
  	if ( name->len > NAME_MAX )
  		return -ENOENT;
  
  	for ( wq = sbi->queues ; wq ; wq = wq->next ) {
  		if ( wq->hash == name->hash &&
  		     wq->len == name->len &&
  		     wq->name && !memcmp(wq->name,name->name,name->len) )
  			break;
  	}
  	
  	if ( !wq ) {
  		/* Create a new wait queue */
  		wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
  		if ( !wq )
  			return -ENOMEM;
  
  		wq->name = kmalloc(name->len,GFP_KERNEL);
  		if ( !wq->name ) {
  			kfree(wq);
  			return -ENOMEM;
  		}
  		wq->wait_queue_token = autofs_next_wait_queue++;
  		init_waitqueue_head(&wq->queue);
  		wq->hash = name->hash;
  		wq->len = name->len;
  		wq->status = -EINTR; /* Status return if interrupted */
  		memcpy(wq->name, name->name, name->len);
  		wq->next = sbi->queues;
  		sbi->queues = wq;
  
  		/* autofs_notify_daemon() may block */
  		wq->wait_ctr = 2;
  		autofs_notify_daemon(sbi,wq);
  	} else
  		wq->wait_ctr++;
  
  	/* wq->name is NULL if and only if the lock is already released */
  
  	if ( sbi->catatonic ) {
  		/* We might have slept, so check again for catatonic mode */
  		wq->status = -ENOENT;

  		kfree(wq->name);
  		wq->name = NULL;

  	}
  
  	if ( wq->name ) {
  		/* Block all but "shutdown" signals while waiting */
  		sigset_t sigmask;
  
  		siginitsetinv(&sigmask, SHUTDOWN_SIGS);
  		sigprocmask(SIG_BLOCK, &sigmask, &sigmask);
  
  		interruptible_sleep_on(&wq->queue);
  
  		sigprocmask(SIG_SETMASK, &sigmask, NULL);
  	} else {
  		DPRINTK(("autofs_wait: skipped sleeping
  "));
  	}
  
  	status = wq->status;
  
  	if ( ! --wq->wait_ctr )	/* Are we the last process to need status? */
  		kfree(wq);
  
  	return status;
  }
  
  
  int autofs_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
  {
  	struct autofs_wait_queue *wq, **wql;
  
  	for ( wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next ) {
  		if ( wq->wait_queue_token == wait_queue_token )
  			break;
  	}
  	if ( !wq )
  		return -EINVAL;
  
  	*wql = wq->next;	/* Unlink from chain */
  	kfree(wq->name);
  	wq->name = NULL;	/* Do not wait on this queue */
  
  	wq->status = status;
  
  	if ( ! --wq->wait_ctr )	/* Is anyone still waiting for this guy? */
  		kfree(wq);
  	else
  		wake_up(&wq->queue);
  
  	return 0;
  }