On Tue, Aug 30, 2016 at 02:56:17PM -0700, Dan Williams wrote: > On Mon, Aug 29, 2016 at 11:52 AM, Matthew Wilcox <mawil...@microsoft.com> > wrote: > > It may be protected by the mapping lock in the current code, but I would it > > expect it to become an RCU lookup + lock eventually. No mapping lock, just > > like the page cache. > > > > Even if we can work around it, why do we want to? What's the compelling > > reason to change from the current radix tree representation of order-N > > entries to an arbitrary range? There are no in-kernel users right now; is > > there a performance reason to change? We don't usually change an API in > > anticipation of future users appearing, particularly when the API makes it > > harder for the existing users to use it. > > I'd use a fill range api for the radix backing get_dev_pagemap() and > potentially another use in device-dax. It centralizes the common > routine of breaking down a range into its constituent power-of-2 > ranges.
Does your usage not work with the current sibling & canonical entry model?
