On Fri, May 12, 2023 at 09:08:54AM -0600, Jens Axboe wrote: > On 5/12/23 9:03?AM, Ming Lei wrote: > > Passthrough(pt) request shouldn't be queued to scheduler, especially some > > schedulers(such as bfq) supposes that req->bio is always available and > > blk-cgroup can be retrieved via bio. > > > > Sometimes pt request could be part of error handling, so it is better to always > > queue it into hctx->dispatch directly. > > > > Fix this issue by queuing pt request from plug list to hctx->dispatch > > directly. > > Why not just add the check to the BFQ insertion? That would be a lot > more trivial and would not be poluting the core with this stuff. Because we really need to keep the passthrough code separate. The fact that a passthrough request can leak into common code in various places is really a bit of a problem. We have most of these nicely separate with two exceptions: - the plug list - the requeue list The higher level and the more obvious we special case the passthrough request there, the better for debuggability and maintainability.
