On Mon, Aug 29, 2016 at 11:52 AM, Matthew Wilcox <[email protected]> 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.
