get rid of autofs_getpath()

allow wq->name.name to point not at the beginning of the object containing
the string, with wq->offset telling how far into it we are.  Then we can
bloody well just use dentry_path_raw() instead of autofs_getpath() -
the only real difference is that dentry_path_raw() puts the result into
the end of buffer and returns where it starts.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/autofs/autofs_i.h

@@ -87,6 +87,7 @@ struct autofs_wait_queue {
 	autofs_wqt_t wait_queue_token;
 	/* We use the following to see what we are waiting for */
 	struct qstr name;
+	u32 offset;
 	u32 dev;
 	u64 ino;
 	kuid_t uid;

fs/autofs/waitq.c

@@ -30,7 +30,7 @@ void autofs_catatonic_mode(struct autofs_sb_info *sbi)
 	while (wq) {
 		nwq = wq->next;
 		wq->status = -ENOENT; /* Magic is gone - report failure */
-		kfree(wq->name.name);
+		kfree(wq->name.name - wq->offset);
 		wq->name.name = NULL;
 		wq->wait_ctr--;
 		wake_up_interruptible(&wq->queue);
@@ -175,51 +175,6 @@ static void autofs_notify_daemon(struct autofs_sb_info *sbi,
 	fput(pipe);
 }
 
-static int autofs_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 *
 autofs_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
 {
@@ -352,6 +307,7 @@ int autofs_wait(struct autofs_sb_info *sbi,
 	struct qstr qstr;
 	char *name;
 	int status, ret, type;
+	unsigned int offset = 0;
 	pid_t pid;
 	pid_t tgid;
 
@@ -389,20 +345,23 @@ int autofs_wait(struct autofs_sb_info *sbi,
 		return -ENOMEM;
 
 	/* If this is a direct mount request create a dummy name */
-	if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
+	if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type)) {
+		qstr.name = name;
 		qstr.len = sprintf(name, "%p", dentry);
-	else {
-		qstr.len = autofs_getpath(sbi, dentry, name);
-		if (!qstr.len) {
+	} else {
+		char *p = dentry_path_raw(dentry, name, NAME_MAX);
+		if (IS_ERR(p)) {
 			kfree(name);
 			return -ENOENT;
 		}
+		qstr.name = ++p; // skip the leading slash
+		qstr.len = strlen(p);
+		offset = p - name;
 	}
-	qstr.name = name;
 	qstr.hash = full_name_hash(dentry, name, qstr.len);
 
 	if (mutex_lock_interruptible(&sbi->wq_mutex)) {
-		kfree(qstr.name);
+		kfree(name);
 		return -EINTR;
 	}
 
@@ -410,7 +369,7 @@ int autofs_wait(struct autofs_sb_info *sbi,
 	if (ret <= 0) {
 		if (ret != -EINTR)
 			mutex_unlock(&sbi->wq_mutex);
-		kfree(qstr.name);
+		kfree(name);
 		return ret;
 	}
 
@@ -418,7 +377,7 @@ int autofs_wait(struct autofs_sb_info *sbi,
 		/* Create a new wait queue */
 		wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
 		if (!wq) {
-			kfree(qstr.name);
+			kfree(name);
 			mutex_unlock(&sbi->wq_mutex);
 			return -ENOMEM;
 		}
@@ -430,6 +389,7 @@ int autofs_wait(struct autofs_sb_info *sbi,
 		sbi->queues = wq;
 		init_waitqueue_head(&wq->queue);
 		memcpy(&wq->name, &qstr, sizeof(struct qstr));
+		wq->offset = offset;
 		wq->dev = autofs_get_dev(sbi);
 		wq->ino = autofs_get_ino(sbi);
 		wq->uid = current_uid();
@@ -469,7 +429,7 @@ int autofs_wait(struct autofs_sb_info *sbi,
 			 (unsigned long) wq->wait_queue_token, wq->name.len,
 			 wq->name.name, notify);
 		mutex_unlock(&sbi->wq_mutex);
-		kfree(qstr.name);
+		kfree(name);
 	}
 
 	/*
@@ -540,7 +500,7 @@ int autofs_wait_release(struct autofs_sb_info *sbi,
 	}
 
 	*wql = wq->next;	/* Unlink from chain */
-	kfree(wq->name.name);
+	kfree(wq->name.name - wq->offset);
 	wq->name.name = NULL;	/* Do not wait on this queue */
 	wq->status = status;
 	wake_up(&wq->queue);