On Tue, Jan 17, 2017 at 09:25:33PM -0800, willy@bombadil.infradead.org wrote:

On Fri, Jan 13, 2017 at 05:20:08PM -0700, Ross Zwisler wrote:

quoted

We still have a lot of work to do, though, and I'd like to propose a discussion
around what features people would like to see enabled in the coming year as
well as what what use cases their customers have that we might not be aware of.

+1 to the discussion

quoted

- Jan suggested [2] that we could use the radix tree as a cache to service DAX
  faults without needing to call into the filesystem.  Are there any issues
  with this approach, and should we move forward with it as an optimization?

Ahem.  I believe I proposed this at last year's LSFMM.  And I sent
patches to start that work.  And Dan blocked it.  So I'm not terribly
amused to see somebody else given credit for the idea.

It's not just an optimisation.  It's also essential for supporting
filesystems which don't have block devices.  I'm aware of at least two
customer demands for this in different domains.

1. Embedded uses with NOR flash
2. Cloud/virt uses with multiple VMs on a single piece of hardware

Yea, I didn't mean the full move to having PFNs in the tree, just using the
sector number in the radix tree instead of calling into the filesystem.

My apologies if you feel I didn't give you proper credit.