On Sun, Aug 15, 2010 at 09:02:30PM +0200, Christoph Hellwig wrote:
> On Sun, Aug 15, 2010 at 01:39:06PM -0400, Ted Ts'o wrote:
> > So after these ordering flush/ordering change that have been proposed,
> > if the block device layer is free to reorder the discard and a
> > subsequent write to a discard block, I will need to add a *new* wait
> > for the discard to complete before I can free the busy extent list.
> > And this will be true for all file systems that are currently issuing
> > discards. Again, am I missing something?
>
> The above is correct, except for the *new* part. sb_issue_discard at
> the moment is synchronous, so you're already waiting for it to finish.
OK, now I understand why I'm confused. I thought the proposal was to
change sb_issue_discard() to make it be asynchronous? Really, what
we're talking about here is eliminating the explicit
barrier/SYNCHRONIZE CACHE from the discard, correct? The
sb_issue_discard() call will still remain synchronous.
- Ted
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