Messages in this thread Patch in this message |  | | | Date | Mon, 5 Mar 2012 09:20:00 -0800 | | From | Tejun Heo <> | | Subject | Re: [PATCHSET] mempool, percpu, blkcg: fix percpu stat allocation and remove stats_lock |
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Hello, Vivek.
Sorry about the delay. Was off last week.
On Wed, Feb 29, 2012 at 02:03:54PM -0500, Vivek Goyal wrote: > Ok, more debugging revealed that culprit here is "floppy" driver module. > It instanciates a queue but never registers a disk against it. Better > skip such queues/groups. Here is the patch.
Urgh.. I hate that driver. I ended up folding the following patch in the series right after "blkcg: kill the mind-bending blkg->dev".
Thanks.
Subject: blkcg: skip blkg printing if q isn't associated with disk
blk-cgroup printing code currently assumes that there is a device/disk associated with every queue in the system, but modules like floppy, can instantiate request queues without registering disk which can lead to oops.
Skip the queue/blkg which don't have dev/disk associated with them.
-tj: Factored out backing_dev_info check into blkg_dev_name().
Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org> --- block/blk-cgroup.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) Index: work/block/blk-cgroup.c =================================================================== --- work.orig/block/blk-cgroup.c +++ work/block/blk-cgroup.c @@ -951,13 +951,24 @@ static int blkiocg_file_write(struct cgr return ret; } +static const char *blkg_dev_name(struct blkio_group *blkg) +{ + /* some drivers (floppy) instantiate a queue w/o disk registered */ + if (blkg->q->backing_dev_info.dev) + return dev_name(blkg->q->backing_dev_info.dev); + return NULL; +} + static void blkio_print_group_conf(struct cftype *cft, struct blkio_group *blkg, struct seq_file *m) { - const char *dname = dev_name(blkg->q->backing_dev_info.dev); + const char *dname = blkg_dev_name(blkg); int fileid = BLKIOFILE_ATTR(cft->private); int rw = WRITE; + if (!dname) + return; + switch (blkg->plid) { case BLKIO_POLICY_PROP: if (blkg->conf.weight) @@ -1049,9 +1060,9 @@ static int blkio_read_blkg_stats(struct rcu_read_lock(); hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) { - const char *dname = dev_name(blkg->q->backing_dev_info.dev); + const char *dname = blkg_dev_name(blkg); - if (BLKIOFILE_POLICY(cft->private) != blkg->plid) + if (!dname || BLKIOFILE_POLICY(cft->private) != blkg->plid) continue; if (pcpu) cgroup_total += blkio_get_stat_cpu(blkg, cb, dname,
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