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Re: don't use wapbl (-o log) on / (/dev)

On Mon, Feb 16, 2009 at 09:24:11AM +0900, YAMAMOTO Takashi wrote:
> > I'm inclined to think a big part of it is that the buffer cache tries
> > (to support LFS) to be virtually indexed and never physically indexed;
> > that is, all buffers belong to vnodes and file offsets rather than
> > devices and device offsets. The problem is that this doesn't work for

and UDF yes

> > I think the buffer cache needs to be restructured so it can be either
> > virtually or physically indexed. This is going to be a big hassle.

i think the easiest way is to make the buffer cache virtually indexed only
since its file granularity that you want to cache on. It does not make sense
to cache a large file when its contents is already deleted. A Physical block
cache needs to exist in the discs device driver, not in a FS.

The transition to virtual indexed cache is almost trivial; FFS stores its
indirect blocks as *negative* indexes already f.e. (yuck, but what to do about
it now).

> actually filesystems can use any kind of numbers as buffer cache index
> for their own vnodes.

Indeed, see FFS

> i don't understand how you think it's related to the bug, tho.

I didn't follow the start of the conversation, so no comment here.

With regards,

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