btrfs: initialize ret to -ENOSPC at __reserve_bytes()

At space-info.c:__reserve_bytes(), instead of initializing 'ret' to 0 when
it's declared and then shortly after set it to -ENOSPC under the space
info's spinlock, initialize it to -ENOSPC when declaring it.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/space-info.c

@@ -1599,7 +1599,7 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info,
 	struct reserve_ticket ticket;
 	u64 start_ns = 0;
 	u64 used;
-	int ret = 0;
+	int ret = -ENOSPC;
 	bool pending_tickets;
 
 	ASSERT(orig_bytes);
@@ -1622,7 +1622,6 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info,
 		async_work = &fs_info->async_reclaim_work;
 
 	spin_lock(&space_info->lock);
-	ret = -ENOSPC;
 	used = btrfs_space_info_used(space_info, true);
 
 	/*