From: Tejun Heo <tj@kernel.org>
Date: Mon, 5 Mar 2012 21:15:19 +0000 (-0800)
Subject: blkcg: let blkcg core manage per-queue blkg list and counter
X-Git-Tag: v3.5-rc1~42^2~67
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=03aa264ac15637b6f98374270bcdf31400965505;p=pandora-kernel.git

blkcg: let blkcg core manage per-queue blkg list and counter

With the previous patch to move blkg list heads and counters to
request_queue and blkg, logic to manage them in both policies are
almost identical and can be moved to blkcg core.

This patch moves blkg link logic into blkg_lookup_create(), implements
common blkg unlink code in blkg_destroy(), and updates
blkg_destory_all() so that it's policy specific and can skip root
group.  The updated blkg_destroy_all() is now used to both clear queue
for bypassing and elv switching, and release all blkgs on q exit.

This patch introduces a race window where policy [de]registration may
race against queue blkg clearing.  This can only be a problem on cfq
unload and shouldn't be a real problem in practice (and we have many
other places where this race already exists).  Future patches will
remove these unlikely races.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

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