Re: [PATCH 1/3] zpool: add zpool_has_pool()

[Seth Jennings]

On Thu, Aug 06, 2015 at 04:50:23PM -0500, Seth Jennings wrote:
> On Wed, Aug 05, 2015 at 03:06:59PM -0700, Andrew Morton wrote:
> > On Wed, 5 Aug 2015 18:00:26 -0400 Dan Streetman <ddstreet@xxxxxxxx> wrote:
> > 
> > > >
> > > > If there's some reason why this can't happen, can we please have a code
> > > > comment which reveals that reason?
> > > 
> > > zpool_create_pool() should work if this returns true, unless as you
> > > say the module is rmmod'ed *and* removed from the system - since
> > > zpool_create_pool() will call request_module() just as this function
> > > does.  I can add a comment explaining that.
> > 
> > I like comments ;)
> > 
> > Seth, I'm planning on sitting on these patches until you've had a
> > chance to review them.
> 
> Thanks Andrew.  I'm reviewing now.  Patch 2/3 is pretty huge.  I've got
> the gist of the changes now.  I'm also building and testing for myself
> as this creates a lot more surface area for issues, alternating between
> compressors and allocating new compression transforms on the fly.
> 
> I'm kinda with Sergey on this in that it adds yet another complexity to
> an already complex feature.  This adds more locking, more RCU, more
> refcounting.  It's becoming harder to review, test, and verify.
> 
> I should have results tomorrow.

So I gave it a test run turning all the knobs (compressor, enabled,
max_pool_percent, and zpool) like a crazy person and it was stable,
and all the adjustments had the expected result.

Dan, you might follow up with an update to Documentation/vm/zswap.txt
noting that these parameters are runtime adjustable now.

The growing complexity is a concern, but it is nice to have the
flexibility.  Thanks for the good work!

To patchset:

Acked-by: Seth Jennings <sjennings@xxxxxxxxxxxxxx>

> 
> Thanks,
> Seth
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