On 11/18/18 6:59 PM, Dave Chinner wrote:

On Sat, Nov 17, 2018 at 04:53:15PM -0700, Jens Axboe wrote:

quoted

Add the field and have the blockdev direct_IO() helpers set it.
This is in preparation for being able to poll for iocb completion.

What purpose does this field serve?

It's for later lookup to find the queue to poll on.

And why add it to just blockdev direct_IO and not the other direct
IO paths, too?

Only block devices support polling.

-- 
Jens Axboe