/* -*- c -*- --------------------------------------------------------------- *
   *
   * linux/fs/autofs/waitq.c
   *
   *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved

   *  Copyright 2001-2006 Ian Kent <raven@themaw.net>

   *
   * 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 autofs4_next_wait_queue = 1;
  
  /* These are the signals we allow interrupting a pending mount */
  #define SHUTDOWN_SIGS	(sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
  
  void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
  {
  	struct autofs_wait_queue *wq, *nwq;
  
  	DPRINTK("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_interruptible(&wq->queue);
  		wq = nwq;
  	}

  	fput(sbi->pipe);	/* Close the pipe */
  	sbi->pipe = NULL;

  }
  
  static int autofs4_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 autofs4_notify_daemon(struct autofs_sb_info *sbi,
  				 struct autofs_wait_queue *wq,
  				 int type)
  {

  	union {
  		struct autofs_packet_hdr hdr;
  		union autofs_packet_union v4_pkt;
  		union autofs_v5_packet_union v5_pkt;
  	} pkt;

  	size_t pktsz;
  
  	DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
  		wq->wait_queue_token, wq->len, wq->name, type);
  
  	memset(&pkt,0,sizeof pkt); /* For security reasons */
  
  	pkt.hdr.proto_version = sbi->version;
  	pkt.hdr.type = type;

  	switch (type) {
  	/* Kernel protocol v4 missing and expire packets */
  	case autofs_ptype_missing:
  	{

  		struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;

  
  		pktsz = sizeof(*mp);
  
  		mp->wait_queue_token = wq->wait_queue_token;
  		mp->len = wq->len;
  		memcpy(mp->name, wq->name, wq->len);
  		mp->name[wq->len] = '\0';

  		break;
  	}
  	case autofs_ptype_expire_multi:
  	{

  		struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;

  
  		pktsz = sizeof(*ep);
  
  		ep->wait_queue_token = wq->wait_queue_token;
  		ep->len = wq->len;
  		memcpy(ep->name, wq->name, wq->len);
  		ep->name[wq->len] = '\0';

  		break;
  	}
  	/*
  	 * Kernel protocol v5 packet for handling indirect and direct
  	 * mount missing and expire requests
  	 */
  	case autofs_ptype_missing_indirect:
  	case autofs_ptype_expire_indirect:
  	case autofs_ptype_missing_direct:
  	case autofs_ptype_expire_direct:
  	{

  		struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;

  
  		pktsz = sizeof(*packet);
  
  		packet->wait_queue_token = wq->wait_queue_token;
  		packet->len = wq->len;
  		memcpy(packet->name, wq->name, wq->len);
  		packet->name[wq->len] = '\0';
  		packet->dev = wq->dev;
  		packet->ino = wq->ino;
  		packet->uid = wq->uid;
  		packet->gid = wq->gid;
  		packet->pid = wq->pid;
  		packet->tgid = wq->tgid;
  		break;
  	}
  	default:

  		printk("autofs4_notify_daemon: bad type %d!
  ", type);
  		return;
  	}
  
  	if (autofs4_write(sbi->pipe, &pkt, pktsz))
  		autofs4_catatonic_mode(sbi);
  }
  
  static int autofs4_getpath(struct autofs_sb_info *sbi,
  			   struct dentry *dentry, char **name)
  {
  	struct dentry *root = sbi->sb->s_root;
  	struct dentry *tmp;
  	char *buf = *name;
  	char *p;
  	int len = 0;
  
  	spin_lock(&dcache_lock);
  	for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
  		len += tmp->d_name.len + 1;
  
  	if (--len > NAME_MAX) {
  		spin_unlock(&dcache_lock);
  		return 0;
  	}
  
  	*(buf + len) = '\0';
  	p = buf + len - dentry->d_name.len;
  	strncpy(p, dentry->d_name.name, dentry->d_name.len);
  
  	for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
  		*(--p) = '/';
  		p -= tmp->d_name.len;
  		strncpy(p, tmp->d_name.name, tmp->d_name.len);
  	}
  	spin_unlock(&dcache_lock);
  
  	return len;
  }

  static struct autofs_wait_queue *
  autofs4_find_wait(struct autofs_sb_info *sbi,
  		  char *name, unsigned int hash, unsigned int len)
  {
  	struct autofs_wait_queue *wq;
  
  	for (wq = sbi->queues; wq; wq = wq->next) {
  		if (wq->hash == hash &&
  		    wq->len == len &&
  		    wq->name && !memcmp(wq->name, name, len))
  			break;
  	}
  	return wq;
  }

  int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
  		enum autofs_notify notify)
  {

  	struct autofs_info *ino;

  	struct autofs_wait_queue *wq;
  	char *name;

  	unsigned int len = 0;
  	unsigned int hash = 0;

  	int status, type;

  
  	/* In catatonic mode, we don't wait for nobody */

  	if (sbi->catatonic)

  		return -ENOENT;
  	
  	name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
  	if (!name)
  		return -ENOMEM;

  	/* If this is a direct mount request create a dummy name */

  	if (IS_ROOT(dentry) && (sbi->type & AUTOFS_TYPE_DIRECT))

  		len = sprintf(name, "%p", dentry);
  	else {
  		len = autofs4_getpath(sbi, dentry, &name);
  		if (!len) {
  			kfree(name);
  			return -ENOENT;
  		}

  	}

  	hash = full_name_hash(name, len);

  	if (mutex_lock_interruptible(&sbi->wq_mutex)) {

  		kfree(name);
  		return -EINTR;
  	}

  	wq = autofs4_find_wait(sbi, name, hash, len);
  	ino = autofs4_dentry_ino(dentry);
  	if (!wq && ino && notify == NFY_NONE) {
  		/*
  		 * Either we've betean the pending expire to post it's
  		 * wait or it finished while we waited on the mutex.
  		 * So we need to wait till either, the wait appears
  		 * or the expire finishes.
  		 */
  
  		while (ino->flags & AUTOFS_INF_EXPIRING) {
  			mutex_unlock(&sbi->wq_mutex);
  			schedule_timeout_interruptible(HZ/10);
  			if (mutex_lock_interruptible(&sbi->wq_mutex)) {
  				kfree(name);
  				return -EINTR;
  			}
  			wq = autofs4_find_wait(sbi, name, hash, len);
  			if (wq)
  				break;
  		}

  		/*
  		 * Not ideal but the status has already gone. Of the two
  		 * cases where we wait on NFY_NONE neither depend on the
  		 * return status of the wait.
  		 */
  		if (!wq) {

  			kfree(name);

  			mutex_unlock(&sbi->wq_mutex);

  			return 0;

  		}

  	}

  	if (!wq) {

  		/* Create a new wait queue */
  		wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);

  		if (!wq) {

  			kfree(name);

  			mutex_unlock(&sbi->wq_mutex);

  			return -ENOMEM;
  		}
  
  		wq->wait_queue_token = autofs4_next_wait_queue;
  		if (++autofs4_next_wait_queue == 0)
  			autofs4_next_wait_queue = 1;
  		wq->next = sbi->queues;
  		sbi->queues = wq;
  		init_waitqueue_head(&wq->queue);

  		wq->hash = hash;

  		wq->name = name;
  		wq->len = len;

  		wq->dev = autofs4_get_dev(sbi);
  		wq->ino = autofs4_get_ino(sbi);
  		wq->uid = current->uid;
  		wq->gid = current->gid;
  		wq->pid = current->pid;
  		wq->tgid = current->tgid;

  		wq->status = -EINTR; /* Status return if interrupted */
  		atomic_set(&wq->wait_ctr, 2);

  		mutex_unlock(&sbi->wq_mutex);

  		if (sbi->version < 5) {
  			if (notify == NFY_MOUNT)
  				type = autofs_ptype_missing;
  			else
  				type = autofs_ptype_expire_multi;
  		} else {
  			if (notify == NFY_MOUNT)

  				type = (sbi->type & AUTOFS_TYPE_DIRECT) ?

  					autofs_ptype_missing_direct :
  					 autofs_ptype_missing_indirect;
  			else

  				type = (sbi->type & AUTOFS_TYPE_DIRECT) ?

  					autofs_ptype_expire_direct :
  					autofs_ptype_expire_indirect;
  		}

  		DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d
  ",
  			(unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);

  
  		/* autofs4_notify_daemon() may block */
  		autofs4_notify_daemon(sbi, wq, type);

  	} else {
  		atomic_inc(&wq->wait_ctr);
  		mutex_unlock(&sbi->wq_mutex);
  		kfree(name);
  		DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
  			(unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);

  	}

  	/* 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 oldset;
  		unsigned long irqflags;
  
  		spin_lock_irqsave(&current->sighand->siglock, irqflags);
  		oldset = current->blocked;
  		siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
  		recalc_sigpending();
  		spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
  
  		wait_event_interruptible(wq->queue, wq->name == NULL);
  
  		spin_lock_irqsave(&current->sighand->siglock, irqflags);
  		current->blocked = oldset;
  		recalc_sigpending();
  		spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
  	} else {
  		DPRINTK("skipped sleeping");
  	}
  
  	status = wq->status;
  
  	/* Are we the last process to need status? */
  	if (atomic_dec_and_test(&wq->wait_ctr))
  		kfree(wq);
  
  	return status;
  }
  
  
  int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
  {
  	struct autofs_wait_queue *wq, **wql;

  	mutex_lock(&sbi->wq_mutex);

  	for (wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next) {
  		if (wq->wait_queue_token == wait_queue_token)

  			break;
  	}

  	if (!wq) {

  		mutex_unlock(&sbi->wq_mutex);

  		return -EINVAL;
  	}
  
  	*wql = wq->next;	/* Unlink from chain */

  	mutex_unlock(&sbi->wq_mutex);

  	kfree(wq->name);
  	wq->name = NULL;	/* Do not wait on this queue */
  
  	wq->status = status;
  
  	if (atomic_dec_and_test(&wq->wait_ctr))	/* Is anyone still waiting for this guy? */
  		kfree(wq);
  	else
  		wake_up_interruptible(&wq->queue);
  
  	return 0;
  }