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authorTejun Heo <tj@kernel.org>2012-03-06 01:15:09 +0400
committerJens Axboe <axboe@kernel.dk>2012-03-07 00:27:22 +0400
commit7a4dd281ec66224f802093962d1d903d86b09560 (patch)
treec38c5c40464d4d7eb429cc14348a435176832ef2 /block/cfq-iosched.c
parent4bfd482e73b30284cb21e10834ce729fa81aa256 (diff)
downloadlinux-7a4dd281ec66224f802093962d1d903d86b09560.tar.xz
blkcg: kill the mind-bending blkg->dev
blkg->dev is dev_t recording the device number of the block device for the associated request_queue. It is used to identify the associated block device when printing out configuration or stats. This is redundant to begin with. A blkg is an association between a cgroup and a request_queue and it of course is possible to reach request_queue from blkg and synchronization conventions are in place for safe q dereferencing, so this shouldn't be necessary from the beginning. Furthermore, it's initialized by sscanf()ing the device name of backing_dev_info. The mind boggles. Anyways, if blkg is visible under rcu lock, we *know* that the associated request_queue hasn't gone away yet and its bdi is registered and alive - blkg can't be created for request_queue which hasn't been fully initialized and it can't go away before blkg is removed. Let stat and conf read functions get device name from blkg->q->backing_dev_info.dev and pass it down to printing functions and remove blkg->dev. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/cfq-iosched.c')
-rw-r--r--block/cfq-iosched.c21
1 files changed, 0 insertions, 21 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 08d4fdd188fa..f67d109eb974 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1052,20 +1052,7 @@ static void cfq_link_blkio_group(struct request_queue *q,
struct blkio_group *blkg)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
- struct backing_dev_info *bdi = &q->backing_dev_info;
struct cfq_group *cfqg = cfqg_of_blkg(blkg);
- unsigned int major, minor;
-
- /*
- * Add group onto cgroup list. It might happen that bdi->dev is
- * not initialized yet. Initialize this new group without major
- * and minor info and this info will be filled in once a new thread
- * comes for IO.
- */
- if (bdi->dev) {
- sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
- blkg->dev = MKDEV(major, minor);
- }
cfqd->nr_blkcg_linked_grps++;
@@ -1104,7 +1091,6 @@ static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
struct blkio_cgroup *blkcg)
{
struct request_queue *q = cfqd->queue;
- struct backing_dev_info *bdi = &q->backing_dev_info;
struct cfq_group *cfqg = NULL;
/* avoid lookup for the common case where there's no blkio cgroup */
@@ -1118,13 +1104,6 @@ static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
cfqg = cfqg_of_blkg(blkg);
}
- if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
- unsigned int major, minor;
-
- sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
- cfqg->blkg.dev = MKDEV(major, minor);
- }
-
return cfqg;
}