fs/autofs4/waitq.c - kernel/bruno - Git at Google

 /* -*- 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 */
 		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 = __vfs_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;

 	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;
 		struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;

 		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 = from_kuid_munged(user_ns, wq->uid);
 		packet->gid = from_kgid_munged(user_ns, wq->gid);
 		packet->pid = wq->pid;
 		packet->tgid = wq->tgid;
 		break;
 	}
 	default:
 		printk("autofs4_notify_daemon: bad type %d!\n", type);
 		mutex_unlock(&sbi->wq_mutex);
 		return;
 	}

 	pipe = get_file(sbi->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 (d_really_is_positive(dentry) && 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;
 	pid_t pid;
 	pid_t tgid;

 	/* In catatonic mode, we don't wait for nobody */
 	if (sbi->catatonic)
 		return -ENOENT;

 	/*
 	 * Try translating pids to the namespace of the daemon.
 	 *
 	 * Zero means failure: we are in an unrelated pid namespace.
 	 */
 	pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 	tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 	if (pid == 0 || tgid == 0)
 		return -ENOENT;

 	if (d_really_is_negative(dentry)) {
 		/*
 		 * 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 = pid;
 		wq->tgid = tgid;
 		wq->status = -EINTR; /* Status return if interrupted */
 		wq->wait_ctr = 2;

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

 		/* autofs4_notify_daemon() may block; it will unlock ->wq_mutex */
 		autofs4_notify_daemon(sbi, wq, type);
 	} else {
 		wq->wait_ctr++;
 		DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 			(unsigned long) wq->wait_queue_token, wq->name.len,
 			wq->name.name, notify);
 		mutex_unlock(&sbi->wq_mutex);
 		kfree(qstr.name);
 	}

 	/*
 	 * 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;
 }
	/* -- 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 */
	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 = __vfs_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;

	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;
	struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;

	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 = from_kuid_munged(user_ns, wq->uid);
	packet->gid = from_kgid_munged(user_ns, wq->gid);
	packet->pid = wq->pid;
	packet->tgid = wq->tgid;
	break;
	}
	default:
	printk("autofs4_notify_daemon: bad type %d!\n", type);
	mutex_unlock(&sbi->wq_mutex);
	return;
	}

	pipe = get_file(sbi->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 (d_really_is_positive(dentry) && 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;
	pid_t pid;
	pid_t tgid;

	/* In catatonic mode, we don't wait for nobody */
	if (sbi->catatonic)
	return -ENOENT;

	/*
	* Try translating pids to the namespace of the daemon.
	*
	* Zero means failure: we are in an unrelated pid namespace.
	*/
	pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
	tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
	if (pid == 0 \|\| tgid == 0)
	return -ENOENT;

	if (d_really_is_negative(dentry)) {
	/*
	* 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 = pid;
	wq->tgid = tgid;
	wq->status = -EINTR; /* Status return if interrupted */
	wq->wait_ctr = 2;

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

	/* autofs4_notify_daemon() may block; it will unlock ->wq_mutex */
	autofs4_notify_daemon(sbi, wq, type);
	} else {
	wq->wait_ctr++;
	DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
	(unsigned long) wq->wait_queue_token, wq->name.len,
	wq->name.name, notify);
	mutex_unlock(&sbi->wq_mutex);
	kfree(qstr.name);
	}

	/*
	* 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;
	}