On 10/19/18 5:19 AM, Avri Altman wrote:

There are 6 writehint types, but the size of the write_hints array
in the request queue is BLK_MAX_WRITE_HINTS = 5,
which causes the EXTREME type to be ignored when iterating
over the hints.

We only have effectively 5 hints.
Bundle together NONE and NOT_SET, since they end up in the same
bucket on the driver side.

fixes: f793dfd3f39a (blk-mq: expose write hints through debugfs)

This isn't right, you can't just redefine the user API. Looking at
the whole thing, I don't think there's a bug. We have 5 hints,
as mentioned in my previous reply - 4 valid ones, and 1 none. If
you look at the only current user of streams, NVMe, it already
bundles NONE and NOT_SET into 0. Hence there's no bug.

-- 
Jens Axboe