Re: O_DIRECT please; Sybase 12.5

[Andrea Arcangeli]

On Fri, Jul 06, 2001 at 12:28:15AM +1000, Andrew Morton wrote:
> ext3 journals data.  That's unique and it breaks things (or rather,
> things break it).   It'd be trivial to support O_DIRECT in ext3's
> writeback mode (metadata-only), but nobody uses that.

I thought everybody uses metadata-only to avoid killing data-write
performance. So I thought it was ok to at first support O_DIRECT only
for metadata journaling, doing that should be a three liner as you said
and that is what I expected.

> >From a quick look it seems that we'll need fs-private implementations
> of generic_direct_IO() and brw_kiovec() at least.

brw_kiovec is called by generic_direct_IO, so yes, all you need is a
private generic_direct_IO implementation to deal with the journaled data
writes.

> I'll take a closer look.

OK, thanks!

Andrea