Hi,
I've just completed cgroups support, and I'd like to highlight the
main blk-mq issue that I have found along the way. I have pushed the
commit that completes the support for cgroups to the usual WIP branch
[1]. Before moving to this issue, I have preliminary question about
the scheduler name, since I'm about to start preparing the patch
series for submission. So far, I have used bfq-mq as a temporary
name. Are we fine with it, or should I change it, for example, to
just bfq? Jens?
I've found a sort of circular dependency in blk-mq, related to
scheduler initialization. To describe both the issue and how I've
addressed it, I'm pasting the message of the new commit.
This commit completes cgroups support for bfq-mq. In particular, it deals with
a sort of circular dependency introduced in blk-mq: the function
blkcg_activate_policy, invoked during scheduler initialization, triggers the
invocation of the has_work scheduler hook (before the init function is
finished). To adress this issue, this commit moves the invocation of
blkcg_activate_policy after the initialization of all the fields that could be
initialized before invoking blkcg_activate_policy itself. This enables has_work
to correctly return false, and thus to prevent the blk-mq stack from invoking
further scheduler hooks before the init function is finished.
Thanks,
Paolo
[1] https://github.com/Algodev-github/bfq-mq
