delousing target_core_file a bit

* set_fs(KERNEL_DS) + getname() is probably the weirdest implementation
of strdup() I've seen.  Especially since they don't to copy it at all...
* filp_open() never returns NULL; it's ERR_PTR(-E...) on failure.
* file->f_dentry is never going to be NULL, TYVM.
* match_strdup() + snprintf() + kfree() is a bloody weird way to spell
match_strlcpy().

Pox on cargo-cult programmers...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/target/target_core_file.c

@@ -109,46 +109,29 @@ static struct se_device *fd_create_virtdevice(
 	struct se_subsystem_dev *se_dev,
 	void *p)
 {
-	char *dev_p = NULL;
 	struct se_device *dev;
 	struct se_dev_limits dev_limits;
 	struct queue_limits *limits;
 	struct fd_dev *fd_dev = p;
 	struct fd_host *fd_host = hba->hba_ptr;
-	mm_segment_t old_fs;
 	struct file *file;
 	struct inode *inode = NULL;
 	int dev_flags = 0, flags, ret = -EINVAL;
 
 	memset(&dev_limits, 0, sizeof(struct se_dev_limits));
 
-	old_fs = get_fs();
-	set_fs(get_ds());
-	dev_p = getname(fd_dev->fd_dev_name);
-	set_fs(old_fs);
-
-	if (IS_ERR(dev_p)) {
-		pr_err("getname(%s) failed: %lu\n",
-			fd_dev->fd_dev_name, IS_ERR(dev_p));
-		ret = PTR_ERR(dev_p);
-		goto fail;
-	}
 	/*
 	 * Use O_DSYNC by default instead of O_SYNC to forgo syncing
 	 * of pure timestamp updates.
 	 */
 	flags = O_RDWR | O_CREAT | O_LARGEFILE | O_DSYNC;
 
-	file = filp_open(dev_p, flags, 0600);
+	file = filp_open(fd_dev->fd_dev_name, flags, 0600);
 	if (IS_ERR(file)) {
-		pr_err("filp_open(%s) failed\n", dev_p);
+		pr_err("filp_open(%s) failed\n", fd_dev->fd_dev_name);
 		ret = PTR_ERR(file);
 		goto fail;
 	}
-	if (!file || !file->f_dentry) {
-		pr_err("filp_open(%s) failed\n", dev_p);
-		goto fail;
-	}
 	fd_dev->fd_file = file;
 	/*
 	 * If using a block backend with this struct file, we extract
@@ -212,14 +195,12 @@ static struct se_device *fd_create_virtdevice(
 		" %llu total bytes\n", fd_host->fd_host_id, fd_dev->fd_dev_id,
 			fd_dev->fd_dev_name, fd_dev->fd_dev_size);
 
-	putname(dev_p);
 	return dev;
 fail:
 	if (fd_dev->fd_file) {
 		filp_close(fd_dev->fd_file, NULL);
 		fd_dev->fd_file = NULL;
 	}
-	putname(dev_p);
 	return ERR_PTR(ret);
 }
 
@@ -448,14 +429,11 @@ static ssize_t fd_set_configfs_dev_params(
 		token = match_token(ptr, tokens, args);
 		switch (token) {
 		case Opt_fd_dev_name:
-			arg_p = match_strdup(&args[0]);
-			if (!arg_p) {
-				ret = -ENOMEM;
+			if (match_strlcpy(fd_dev->fd_dev_name, &args[0],
+				FD_MAX_DEV_NAME) == 0) {
+				ret = -EINVAL;
 				break;
 			}
-			snprintf(fd_dev->fd_dev_name, FD_MAX_DEV_NAME,
-					"%s", arg_p);
-			kfree(arg_p);
 			pr_debug("FILEIO: Referencing Path: %s\n",
 					fd_dev->fd_dev_name);
 			fd_dev->fbd_flags |= FBDF_HAS_PATH;