linux-kernel - Re: [PATCH 01/16] blkcg: make CONFIG_BLK

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Date:	Thu, 02 Feb 2012 14:53:57 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	axboe@...nel.dk, vgoyal@...hat.com, ctalbott@...gle.com,
	rni@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/16] blkcg: make CONFIG_BLK_CGROUP bool

Tejun Heo wrote:
> Block cgroup core can be built as module; however, it isn't too useful
> as blk-throttle can only be built-in and cfq-iosched is usually the
> default built-in scheduler.  Scheduled blkcg cleanup requires calling
> into blkcg from block core.  To simplify that, disallow building blkcg
> as module by making CONFIG_BLK_CGROUP bool.
> 
> If building blkcg core as module really matters, which I doubt, we can
> revisit it after blkcg API cleanup.
> 
> -v2: Vivek pointed out that IOSCHED_CFQ was incorrectly updated to
>      depend on BLK_CGROUP.  Fixed.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> ---
>  block/Kconfig.iosched |    4 ----
>  block/blk-cgroup.c    |   17 -----------------
>  block/blk-cgroup.h    |   10 ++--------
>  init/Kconfig          |    2 +-
>  4 files changed, 3 insertions(+), 30 deletions(-)
> 

You can merge the following change with your patch.

Moreover, some cgroup APIs were exported to allow blk-cgroup to be built
as a module, and now they can be unexported.

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index fa8f263..bc8ea70 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -55,9 +55,7 @@ struct cgroup_subsys blkio_subsys = {
 	.subsys_id = blkio_subsys_id,
 #endif
 	.use_id = 1,
-	.module = THIS_MODULE,
 };
-EXPORT_SYMBOL_GPL(blkio_subsys);
 
 static inline void blkio_policy_insert_node(struct blkio_cgroup *blkcg,
 					    struct blkio_policy_node *pn)
@@ -1594,8 +1592,6 @@ static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 
 	free_css_id(&blkio_subsys, &blkcg->css);
 	rcu_read_unlock();
-	if (blkcg != &blkio_root_cgroup)
-		kfree(blkcg);
 }
 
 static struct cgroup_subsys_state *


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