On Mon, Aug 06, 2018 at 02:17:54PM +0800, Qu Wenruo wrote:
> > - u64 objectid;
>
> Off topic crazy idea here.
>
> I think it is a little crazy, but it should save a lot of objectid
> related modification:
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 118346aceea9..e6d70f2309a3 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1166,7 +1166,10 @@ struct btrfs_root {
>
> unsigned long state;
> struct btrfs_root_item root_item;
> - struct btrfs_key root_key;
> + union {
> + struct btrfs_key root_key;
> + u64 objectid;
> + };
> struct btrfs_fs_info *fs_info;
> struct extent_io_tree dirty_log_pages;
>
> @@ -1198,7 +1201,6 @@ struct btrfs_root {
> int last_log_commit;
> pid_t log_start_pid;
>
> - u64 objectid;
> u64 last_trans;
>
> u32 type;
>
> I'm not sure if this is a really crazy idea or a dirty hack to reduce
> some modification.
Be wary of such tricks. This might make you feel good for a moment how
good your C knowlege is, and also might save a few keystrokes. And a few
years later this costs somebody a week of debugging a mysterious memory
corrupption under circumstances not imagined right now.
Try to write understandable code. If there is a reason to use tricks,
like the struct page has to do for performance reasons, then it must be
documented and justified.
