Re: [RFC PATCH 1/3] blk-mq: Reference count request usage

Christoph Hellwig
2018-05-22T15:19:37Z

On Mon, May 21, 2018 at 05:11:29PM -0600, Keith Busch wrote:
> This patch adds a struct kref to struct request so that request users
> can be sure they're operating on the same request without it changing
> while they're processing it. The request's tag won't be released for
> reuse until the last user is done with it.

Can you please use a raw refcount_t instead of the kref? That avoids
a possible indirect call in the fast path, which have become really
painful with the spectre mitigrations, and also is easier to follow
to start with.

I also think this should be merged into patch 3, as it isn't very
useful on its own.