On Fri, May 08, 2020 at 11:04:45AM -0700, Dan Williams wrote:

On Fri, May 8, 2020 at 9:16 AM Christoph Hellwig [off-list ref] wrote:

quoted

Hi all,

various bio based drivers use queue->queuedata despite already having
set up disk->private_data, which can be used just as easily.  This
series cleans them up to only use a single private data pointer.

...but isn't the queue pretty much guaranteed to be cache hot and the
gendisk cache cold? I'm not immediately seeing what else needs the
gendisk in the I/O path. Is there another motivation I'm missing?

->private_data is right next to the ->queue pointer, pat0 and part_tbl
which are all used in the I/O submission path (generic_make_request /
generic_make_request_checks).  This is mostly a prep cleanup patch to
also remove the pointless queue argument from ->make_request - then
->queue is an extra dereference and extra churn.