btrfs: use GFP_KERNEL in btrfs_init_dev_replace_tgtdev

The function is called from ioctl context and we don't hold any locks
that take part in writeback. Right now it's only fs_info::volume_mutex.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index c10d75f..8bb1f4e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2572,7 +2572,7 @@
 		goto error;
 	}
 
-	name = rcu_string_strdup(device_path, GFP_NOFS);
+	name = rcu_string_strdup(device_path, GFP_KERNEL);
 	if (!name) {
 		kfree(device);
 		ret = -ENOMEM;