/* -*- 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;

  	mutex_lock(&sbi->wq_mutex);
  	if (sbi->catatonic) {
  		mutex_unlock(&sbi->wq_mutex);
  		return;
  	}

  	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 */

  		if (wq->name.name) {
  			kfree(wq->name.name);
  			wq->name.name = NULL;
  		}

  		wq->wait_ctr--;

  		wake_up_interruptible(&wq->queue);
  		wq = nwq;
  	}

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

  	sbi->pipefd = -1;
  	mutex_unlock(&sbi->wq_mutex);

  }

  static int autofs4_write(struct autofs_sb_info *sbi,
  			 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;

  	sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  
  	/* Save pointer to user space and point back to kernel space */
  	fs = get_fs();
  	set_fs(KERNEL_DS);

  	mutex_lock(&sbi->pipe_mutex);

  	while (bytes &&
  	       (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  		data += wr;
  		bytes -= wr;
  	}

  	mutex_unlock(&sbi->pipe_mutex);

  
  	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;

  	struct file *pipe = NULL;

  	size_t pktsz;
  
  	DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",

  		(unsigned long) wq->wait_queue_token, wq->name.len, wq->name.name, type);

  
  	memset(&pkt,0,sizeof pkt); /* For security reasons */
  
  	pkt.hdr.proto_version = sbi->version;
  	pkt.hdr.type = type;

  	mutex_lock(&sbi->wq_mutex);
  
  	/* Check if we have become catatonic */
  	if (sbi->catatonic) {
  		mutex_unlock(&sbi->wq_mutex);
  		return;
  	}

  	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->name.len;
  		memcpy(mp->name, wq->name.name, wq->name.len);
  		mp->name[wq->name.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->name.len;
  		memcpy(ep->name, wq->name.name, wq->name.len);
  		ep->name[wq->name.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->name.len;
  		memcpy(packet->name, wq->name.name, wq->name.len);
  		packet->name[wq->name.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);

  		mutex_unlock(&sbi->wq_mutex);

  		return;
  	}

  	pipe = sbi->pipe;
  	get_file(pipe);

  	mutex_unlock(&sbi->wq_mutex);

  	if (autofs4_write(sbi, pipe, &pkt, pktsz))

  		autofs4_catatonic_mode(sbi);
  	fput(pipe);

  }
  
  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;

  	char *p;

  	int len;
  	unsigned seq;
  
  rename_retry:
  	buf = *name;
  	len = 0;

  	seq = read_seqbegin(&rename_lock);
  	rcu_read_lock();

  	spin_lock(&sbi->fs_lock);

  	for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
  		len += tmp->d_name.len + 1;

  	if (!len || --len > NAME_MAX) {

  		spin_unlock(&sbi->fs_lock);

  		rcu_read_unlock();
  		if (read_seqretry(&rename_lock, seq))
  			goto rename_retry;

  		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(&sbi->fs_lock);

  	rcu_read_unlock();
  	if (read_seqretry(&rename_lock, seq))
  		goto rename_retry;

  
  	return len;
  }

  static struct autofs_wait_queue *

  autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)

  {
  	struct autofs_wait_queue *wq;
  
  	for (wq = sbi->queues; wq; wq = wq->next) {

  		if (wq->name.hash == qstr->hash &&
  		    wq->name.len == qstr->len &&
  		    wq->name.name &&
  			 !memcmp(wq->name.name, qstr->name, qstr->len))

  			break;
  	}
  	return wq;
  }

  /*
   * Check if we have a valid request.
   * Returns
   * 1 if the request should continue.
   *   In this case we can return an autofs_wait_queue entry if one is
   *   found or NULL to idicate a new wait needs to be created.
   * 0 or a negative errno if the request shouldn't continue.
   */
  static int validate_request(struct autofs_wait_queue **wait,
  			    struct autofs_sb_info *sbi,
  			    struct qstr *qstr,
  			    struct dentry*dentry, enum autofs_notify notify)
  {
  	struct autofs_wait_queue *wq;
  	struct autofs_info *ino;

  	if (sbi->catatonic)
  		return -ENOENT;

  	/* Wait in progress, continue; */
  	wq = autofs4_find_wait(sbi, qstr);
  	if (wq) {
  		*wait = wq;
  		return 1;
  	}
  
  	*wait = NULL;
  
  	/* If we don't yet have any info this is a new request */
  	ino = autofs4_dentry_ino(dentry);
  	if (!ino)
  		return 1;
  
  	/*
  	 * If we've been asked to wait on an existing expire (NFY_NONE)
  	 * but there is no wait in the queue ...
  	 */
  	if (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))
  				return -EINTR;

  			if (sbi->catatonic)
  				return -ENOENT;

  			wq = autofs4_find_wait(sbi, qstr);
  			if (wq) {
  				*wait = wq;
  				return 1;
  			}
  		}
  
  		/*
  		 * 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.
  		 */
  		return 0;
  	}
  
  	/*
  	 * If we've been asked to trigger a mount and the request
  	 * completed while we waited on the mutex ...
  	 */
  	if (notify == NFY_MOUNT) {

  		struct dentry *new = NULL;
  		int valid = 1;

  		/*

  		 * If the dentry was successfully mounted while we slept
  		 * on the wait queue mutex we can return success. If it
  		 * isn't mounted (doesn't have submounts for the case of
  		 * a multi-mount with no mount at it's base) we can
  		 * continue on and create a new request.
  		 */

  		if (!IS_ROOT(dentry)) {
  			if (dentry->d_inode && d_unhashed(dentry)) {
  				struct dentry *parent = dentry->d_parent;
  				new = d_lookup(parent, &dentry->d_name);
  				if (new)
  					dentry = new;
  			}
  		}

  		if (have_submounts(dentry))

  			valid = 0;
  
  		if (new)
  			dput(new);
  		return valid;

  	}
  
  	return 1;
  }

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

  	struct qstr qstr;

  	char *name;

  	int status, ret, type;

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

  	if (sbi->catatonic)

  		return -ENOENT;

  	if (!dentry->d_inode) {
  		/*
  		 * A wait for a negative dentry is invalid for certain
  		 * cases. A direct or offset mount "always" has its mount
  		 * point directory created and so the request dentry must
  		 * be positive or the map key doesn't exist. The situation
  		 * is very similar for indirect mounts except only dentrys
  		 * in the root of the autofs file system may be negative.
  		 */

  		if (autofs_type_trigger(sbi->type))

  			return -ENOENT;
  		else if (!IS_ROOT(dentry->d_parent))
  			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) && autofs_type_trigger(sbi->type))

  		qstr.len = sprintf(name, "%p", dentry);

  	else {

  		qstr.len = autofs4_getpath(sbi, dentry, &name);
  		if (!qstr.len) {

  			kfree(name);
  			return -ENOENT;
  		}

  	}

  	qstr.name = name;
  	qstr.hash = full_name_hash(name, qstr.len);

  	if (mutex_lock_interruptible(&sbi->wq_mutex)) {
  		kfree(qstr.name);

  		return -EINTR;

  	}

  	ret = validate_request(&wq, sbi, &qstr, dentry, notify);
  	if (ret <= 0) {

  		if (ret != -EINTR)

  			mutex_unlock(&sbi->wq_mutex);

  		kfree(qstr.name);
  		return ret;

  	}

  	if (!wq) {

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

  		if (!wq) {

  			kfree(qstr.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);

  		memcpy(&wq->name, &qstr, sizeof(struct qstr));

  		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 */

  		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 = autofs_type_trigger(sbi->type) ?

  					autofs_ptype_missing_direct :
  					 autofs_ptype_missing_indirect;
  			else

  				type = autofs_type_trigger(sbi->type) ?

  					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->name.len,
  			wq->name.name, notify);

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

  	} else {

  		wq->wait_ctr++;

  		mutex_unlock(&sbi->wq_mutex);

  		kfree(qstr.name);

  		DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",

  			(unsigned long) wq->wait_queue_token, wq->name.len,
  			wq->name.name, notify);

  	}

  	/*
  	 * wq->name.name is NULL iff the lock is already released
  	 * or the mount has been made catatonic.
  	 */

  	if (wq->name.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.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;

  	/*
  	 * For direct and offset mounts we need to track the requester's
  	 * uid and gid in the dentry info struct. This is so it can be
  	 * supplied, on request, by the misc device ioctl interface.
  	 * This is needed during daemon resatart when reconnecting
  	 * to existing, active, autofs mounts. The uid and gid (and
  	 * related string values) may be used for macro substitution
  	 * in autofs mount maps.
  	 */
  	if (!status) {
  		struct autofs_info *ino;
  		struct dentry *de = NULL;
  
  		/* direct mount or browsable map */
  		ino = autofs4_dentry_ino(dentry);
  		if (!ino) {
  			/* If not lookup actual dentry used */
  			de = d_lookup(dentry->d_parent, &dentry->d_name);
  			if (de)
  				ino = autofs4_dentry_ino(de);
  		}
  
  		/* Set mount requester */
  		if (ino) {
  			spin_lock(&sbi->fs_lock);
  			ino->uid = wq->uid;
  			ino->gid = wq->gid;
  			spin_unlock(&sbi->fs_lock);
  		}
  
  		if (de)
  			dput(de);
  	}

  	/* Are we the last process to need status? */

  	mutex_lock(&sbi->wq_mutex);
  	if (!--wq->wait_ctr)

  		kfree(wq);

  	mutex_unlock(&sbi->wq_mutex);

  
  	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) != NULL; 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 */

  	kfree(wq->name.name);
  	wq->name.name = NULL;	/* Do not wait on this queue */

  	wq->status = status;

  	wake_up_interruptible(&wq->queue);
  	if (!--wq->wait_ctr)

  		kfree(wq);

  	mutex_unlock(&sbi->wq_mutex);

  
  	return 0;
  }