Revert "[PATCH] Fix d_path for lazy unmounts"

This reverts commit eb3dfb0c.

It causes some strange Gnome problem with dbus-daemon getting stuck, so
we'll revert it until that problem is understood.

Reported by both walt and Greg KH, who both independently git-bisected
the problem to this commit.

Andreas is looking at it.
Reported-by: walt <wa1ter@myrealbox.com>
Reported-by: Greg KH <greg@kroah.com>
Acked-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/dcache.c

@@ -1739,41 +1739,45 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
  * @rootmnt: vfsmnt to which the root dentry belongs
  * @buffer: buffer to return value in
  * @buflen: buffer length
- * @fail_deleted: what to return for deleted files
  *
- * Convert a dentry into an ASCII path name. If the entry has been deleted,
- * then if @fail_deleted is true, ERR_PTR(-ENOENT) is returned. Otherwise,
- * the the string " (deleted)" is appended. Note that this is ambiguous.
+ * Convert a dentry into an ASCII path name. If the entry has been deleted
+ * the string " (deleted)" is appended. Note that this is ambiguous.
  *
- * Returns the buffer or an error code.
+ * Returns the buffer or an error code if the path was too long.
+ *
+ * "buflen" should be positive. Caller holds the dcache_lock.
  */
-static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
-		      struct dentry *root, struct vfsmount *rootmnt,
-		      char *buffer, int buflen, int fail_deleted)
+static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
+			struct dentry *root, struct vfsmount *rootmnt,
+			char *buffer, int buflen)
 {
-	int namelen, is_slash;
-
-	if (buflen < 2)
-		return ERR_PTR(-ENAMETOOLONG);
-	buffer += --buflen;
-	*buffer = '\0';
+	char * end = buffer+buflen;
+	char * retval;
+	int namelen;
 
-	spin_lock(&dcache_lock);
+	*--end = '\0';
+	buflen--;
 	if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
-		if (fail_deleted) {
-			buffer = ERR_PTR(-ENOENT);
-			goto out;
-		}
-		if (buflen < 10)
-			goto Elong;
 		buflen -= 10;
-		buffer -= 10;
-		memcpy(buffer, " (deleted)", 10);
+		end -= 10;
+		if (buflen < 0)
+			goto Elong;
+		memcpy(end, " (deleted)", 10);
 	}
-	while (dentry != root || vfsmnt != rootmnt) {
+
+	if (buflen < 1)
+		goto Elong;
+	/* Get '/' right */
+	retval = end-1;
+	*retval = '/';
+
+	for (;;) {
 		struct dentry * parent;
 
+		if (dentry == root && vfsmnt == rootmnt)
+			break;
 		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+			/* Global root? */
 			spin_lock(&vfsmount_lock);
 			if (vfsmnt->mnt_parent == vfsmnt) {
 				spin_unlock(&vfsmount_lock);
@@ -1787,60 +1791,33 @@ static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
 		parent = dentry->d_parent;
 		prefetch(parent);
 		namelen = dentry->d_name.len;
-		if (buflen <= namelen)
-			goto Elong;
 		buflen -= namelen + 1;
-		buffer -= namelen;
-		memcpy(buffer, dentry->d_name.name, namelen);
-		*--buffer = '/';
+		if (buflen < 0)
+			goto Elong;
+		end -= namelen;
+		memcpy(end, dentry->d_name.name, namelen);
+		*--end = '/';
+		retval = end;
 		dentry = parent;
 	}
-	/* Get '/' right */
-	if (*buffer != '/')
-		*--buffer = '/';
 
-out:
-	spin_unlock(&dcache_lock);
-	return buffer;
+	return retval;
 
 global_root:
-	/*
-	 * We went past the (vfsmount, dentry) we were looking for and have
-	 * either hit a root dentry, a lazily unmounted dentry, an
-	 * unconnected dentry, or the file is on a pseudo filesystem.
-	 */
 	namelen = dentry->d_name.len;
-	is_slash = (namelen == 1 && *dentry->d_name.name == '/');
-	if (is_slash || (dentry->d_sb->s_flags & MS_NOUSER)) {
-		/*
-		 * Make sure we won't return a pathname starting with '/'.
-		 *
-		 * Historically, we also glue together the root dentry and
-		 * remaining name for pseudo filesystems like pipefs, which
-		 * have the MS_NOUSER flag set. This results in pathnames
-		 * like "pipe:[439336]".
-		 */
-		if (*buffer == '/') {
-			buffer++;
-			buflen++;
-		}
-		if (is_slash)
-			goto out;
-	}
-	if (buflen < namelen)
+	buflen -= namelen;
+	if (buflen < 0)
 		goto Elong;
-	buffer -= namelen;
-	memcpy(buffer, dentry->d_name.name, namelen);
-	goto out;
-
+	retval -= namelen-1;	/* hit the slash */
+	memcpy(retval, dentry->d_name.name, namelen);
+	return retval;
 Elong:
-	buffer = ERR_PTR(-ENAMETOOLONG);
-	goto out;
+	return ERR_PTR(-ENAMETOOLONG);
 }
 
 /* write full pathname into buffer and return start of pathname */
-char *d_path(struct dentry *dentry, struct vfsmount *vfsmnt, char *buf,
-	     int buflen)
+char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
+				char *buf, int buflen)
 {
 	char *res;
 	struct vfsmount *rootmnt;
@@ -1850,7 +1827,9 @@ char *d_path(struct dentry *dentry, struct vfsmount *vfsmnt, char *buf,
 	rootmnt = mntget(current->fs->rootmnt);
 	root = dget(current->fs->root);
 	read_unlock(&current->fs->lock);
-	res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen, 0);
+	spin_lock(&dcache_lock);
+	res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen);
+	spin_unlock(&dcache_lock);
 	dput(root);
 	mntput(rootmnt);
 	return res;
@@ -1876,10 +1855,10 @@ char *d_path(struct dentry *dentry, struct vfsmount *vfsmnt, char *buf,
  */
 asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
 {
-	int error, len;
+	int error;
 	struct vfsmount *pwdmnt, *rootmnt;
 	struct dentry *pwd, *root;
-	char *page = (char *) __get_free_page(GFP_USER), *cwd;
+	char *page = (char *) __get_free_page(GFP_USER);
 
 	if (!page)
 		return -ENOMEM;
@@ -1891,18 +1870,29 @@ asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
 	root = dget(current->fs->root);
 	read_unlock(&current->fs->lock);
 
-	cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE, 1);
-	error = PTR_ERR(cwd);
-	if (IS_ERR(cwd))
-		goto out;
+	error = -ENOENT;
+	/* Has the current directory has been unlinked? */
+	spin_lock(&dcache_lock);
+	if (pwd->d_parent == pwd || !d_unhashed(pwd)) {
+		unsigned long len;
+		char * cwd;
 
-	error = -ERANGE;
-	len = PAGE_SIZE + page - cwd;
-	if (len <= size) {
-		error = len;
-		if (copy_to_user(buf, cwd, len))
-			error = -EFAULT;
-	}
+		cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
+		spin_unlock(&dcache_lock);
+
+		error = PTR_ERR(cwd);
+		if (IS_ERR(cwd))
+			goto out;
+
+		error = -ERANGE;
+		len = PAGE_SIZE + page - cwd;
+		if (len <= size) {
+			error = len;
+			if (copy_to_user(buf, cwd, len))
+				error = -EFAULT;
+		}
+	} else
+		spin_unlock(&dcache_lock);
 
 out:
 	dput(pwd);