Re: [PATCH] 2.6.11-mm3 patch for ext3 writeback "nobh" option

From: Badari Pulavarty
Date: Mon Mar 14 2005 - 15:02:14 EST

On Mon, 2005-03-14 at 11:29, Arjan van de Ven wrote:
> On Mon, 2005-03-14 at 11:18 -0800, Badari Pulavarty wrote:
> > Hi Andrew,
> >
> > Here is the 2.6.11-mm3 version of patch for adding "nobh"
> > support for ext3 writeback mode.
> can you explain why this is an option ? It's not like the on disk layout
> changes or something... is there a reason to ever not want this?

I am slowly trying to reduce the uses of "bufferhead"s in the ext3.
We can get away not attaching a bufferheads for the pages in
ext3 writeback mode easily. But for ordered mode, its doable
but tricky.

There are few cases, I didn't handle in my patch (just to reduce
the code complexity)

- I still create bufferheads for filesystem
blocksize != PAGE_SIZE

- In case of a truncate and the page is not uptodate
(needs to do IO to read the page) - I attach buffers.
I had code to eliminate this - but Andrew didn't like it :(

I want to get more run-time before making it a default.


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