Re: [PATCH] btrfs: use shifts for sectorsize and nodesize

[David Sterba <dsterba@suse.cz>]

On Wed, May 27, 2026 at 09:04:09AM -0700, Boris Burkov wrote:
> > --- a/fs/btrfs/relocation.c
> > +++ b/fs/btrfs/relocation.c
> > @@ -1560,7 +1560,7 @@ static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
> >  	 * and * 2 since we have two trees to COW.
> >  	 */
> >  	reserve_level = max_t(int, 1, btrfs_root_level(root_item));
> > -	min_reserved = fs_info->nodesize * reserve_level * 2;
> > +	min_reserved = (reserve_level << fs_info->nodesize_bits) * 2;
> 
> Is it nicer to just add 1 to the shift operand?

There's fragment of the comment in the diff context, in full

        /*
         * In merge_reloc_root(), we modify the upper level pointer to swap the
         * tree blocks between reloc tree and subvolume tree.  Thus for tree
         * block COW, we COW at most from level 1 to root level for each tree.
         *
         * Thus the needed metadata size is at most root_level * nodesize,
         * and * 2 since we have two trees to COW.
         */

so the "* 2" matches it.