Subject: Re: Porting Hammerfs (fwd)
To: None <,>
From: Thor Lancelot Simon <>
List: tech-kern
Date: 12/11/2007 12:36:57
On Sun, Dec 09, 2007 at 08:44:01PM +0100, Mark Weinem wrote:
> Matthew Dillon about the state of the HAMMER filesystem  and about
> porting to other systems:
> ---------- Forwarded message ----------
> [...]
>     With regards to the OS interface, HAMMER uses 16K filesystem buffers
>     and it shouldn't be too hard to port that part of it.  DragonFly uses
>     64 bit byte offsets for its buffer cache buffers rather than block
>     numbers.  There is one big gotcha, though, and that is I am using an
>     augmented softupdates callback API to allow buffer cache buffers to be
>     passively associated with HAMMER's in-memory structures.  When the OS
>     wants to flush or discard/reuse a buffer, it makes a callback and
>     HAMMER then has the ability to tell the OS NOT to do that by setting
>     B_LOCKED in the bp.

NetBSD doesn't use the buffer cache for file data, so I suspect reproducing
this behavior is considerably more difficult than Matthew expected.