[Drbd-dev] [RFC PATCH 00/32] separate operations from flags in the bio/request structs

[Mike Snitzer]

On Wed, Nov 11 2015 at  6:28am -0500,
Christoph Hellwig <hch at infradead.org> wrote:

> On Wed, Nov 11, 2015 at 01:53:24AM -0600, Mike Christie wrote:
> > We no longer have the bvec merge functions so the original reason given
> > in the thread/patch Bart referenced is no longer valid.
> > 
> > Offlist it was suggested that dropping the argument from submit_bio
> > might still improve performance, but I modified xfs and dm and did some
> > testing and did not see anything.
> > 
> > So the change is not needed, and it would only be done because people
> > feel it would improve the interface.
> 
> I would defintively prefer the changed interface, and to me it also
> looks like it would make your overall patch simpler.  If you disagree
> feel free to keep it as-is for now and I'll do another pass later.

The less churn the better.  But honestly, not quite following the logic
on why all this flag-day churn is needed.  BUT if it needs to happen,
because we'll soon hit a wall on supported operations via REQ_*, now is
as good a time as any -- but best to limit the change to the flags IMHO.