Re: In-kernel units for block numbers, etc ...

[David Holland <dholland-tech%netbsd.org@localhost>]

On Thu, Nov 26, 2015 at 11:25:21PM +0000, Michael van Elst wrote:
 > dholland-tech%netbsd.org@localhost (David Holland) writes:
 > 
 > >The problem I see with carrying around unit values at runtime (besides
 > >potential overhead) is that at least in FS-level code it'll make a
 > >huge mess. FFS, for example, has hardware-level sectors, DEV_BSIZE
 > >blocks, fragments, its own blocks, and maybe other things;
 > 
 > FFS (without WAPBL) has
 > 
 > - a superblock at a byte offset
 > - fragments
 > 
 > All disk I/O except for the superblock is just accessing
 > one or more fragments. Fragment addresses used to be
 > converted to physical sector addresses, but in NetBSD
 > they are converted to DEV_BSIZE adresses when passed
 > to the disk driver. This is done with a single macro.
 > 
 > It's very simple.

Theoretically, perhaps; in practice, I'm sure that macros like "cgtod"
or "dtog" or "lfragtosize" didn't appear with WAPBL.

-- 
David A. Holland
dholland%netbsd.org@localhost