Re: [PATCH 0/4] eliminate SECTOR related magic numbers and duplicated conversions

[Matthew Wilcox]

On Tue, May 05, 2020 at 06:32:36PM +0100, antlists wrote:
> On 05/05/2020 12:55, Zhen Lei wrote:
> > When I studied the code of mm/swap, I found "1 << (PAGE_SHIFT - 9)" appears
> > many times. So I try to clean up it.
> > 
> > 1. Replace "1 << (PAGE_SHIFT - 9)" or similar with SECTORS_PER_PAGE
> > 2. Replace "PAGE_SHIFT - 9" with SECTORS_PER_PAGE_SHIFT
> > 3. Replace "9" with SECTOR_SHIFT
> > 4. Replace "512" with SECTOR_SIZE
> 
> Naive question - what is happening about 4096-byte sectors? Do we need to
> forward-plan?

They're fully supported already, but Linux defines a sector to be 512
bytes.  So we multiply by 8 and divide by 8 a few times unnecessarily,
but it's not worth making sector size be a per-device property.

Good thought, though.