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Subject[PATCH 03/11] blkcg: remove unnecessary blkcg_root handling from css_alloc/free paths
Date
blkcg_css_alloc() bypasses policy data allocation and blkcg_css_free()
bypasses policy data and blkcg freeing for blkcg_root. There's no
reason to to treat policy data any differently for blkcg_root. If the
root css gets allocated after policies are registered, policy
registration path will add policy data; otherwise, the alloc path
will. The free path isn't never invoked for root csses.

This patch removes the unnecessary special handling of blkcg_root from
css_alloc/free paths.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-cgroup.c | 25 ++++++++++---------------
1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 64cc48f..2a493ce 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -819,18 +819,15 @@ static void blkcg_css_offline(struct cgroup_subsys_state *css)
static void blkcg_css_free(struct cgroup_subsys_state *css)
{
struct blkcg *blkcg = css_to_blkcg(css);
+ int i;

mutex_lock(&blkcg_pol_mutex);
list_del(&blkcg->all_blkcgs_node);
mutex_unlock(&blkcg_pol_mutex);

- if (blkcg != &blkcg_root) {
- int i;
-
- for (i = 0; i < BLKCG_MAX_POLS; i++)
- kfree(blkcg->pd[i]);
- kfree(blkcg);
- }
+ for (i = 0; i < BLKCG_MAX_POLS; i++)
+ kfree(blkcg->pd[i]);
+ kfree(blkcg);
}

static struct cgroup_subsys_state *
@@ -844,13 +841,12 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)

if (!parent_css) {
blkcg = &blkcg_root;
- goto done;
- }
-
- blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
- if (!blkcg) {
- ret = ERR_PTR(-ENOMEM);
- goto free_blkcg;
+ } else {
+ blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
+ if (!blkcg) {
+ ret = ERR_PTR(-ENOMEM);
+ goto free_blkcg;
+ }
}

for (i = 0; i < BLKCG_MAX_POLS ; i++) {
@@ -877,7 +873,6 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
pol->cpd_init_fn(blkcg);
}

-done:
spin_lock_init(&blkcg->lock);
INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT);
INIT_HLIST_HEAD(&blkcg->blkg_list);
--
2.4.3


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