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SubjectRe: [PATCH 07/23] io-controller: Common hierarchical fair queuing code in elevaotor layer
Hi,

Vivek Goyal wrote, on 08/28/2009 05:30 PM:
> +static struct io_group *io_find_alloc_group(struct request_queue *q,
> + struct cgroup *cgroup, struct elv_fq_data *efqd,
> + int create)
> +{
> + struct io_cgroup *iocg = cgroup_to_io_cgroup(cgroup);
> + struct io_group *iog = NULL;
> + /* Note: Use efqd as key */
> + void *key = efqd;
> +
> + /*
> + * Take a refenrece to css object. Don't want to map a bio to
> + * a group if it has been marked for deletion
> + */
> +
> + if (!css_tryget(&iocg->css))
> + return iog;

cgroup_to_io_cgroup() returns NULL if only blkio subsystem
is mounted but io subsystem is not. It can cause NULL pointer
access.

Signed-off-by: Munehiro "Muuhh" Ikeda <m-ikeda@ds.jp.nec.com>
---
block/elevator-fq.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index b723c12..6714e73 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -1827,7 +1827,7 @@ static struct io_group *io_find_alloc_group(struct request_queue *q,
* a group if it has been marked for deletion
*/

- if (!css_tryget(&iocg->css))
+ if (!iocg || !css_tryget(&iocg->css))
return iog;

iog = io_cgroup_lookup_group(iocg, key);
--
1.6.2.5

--
IKEDA, Munehiro
NEC Corporation of America
m-ikeda@ds.jp.nec.com



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