From 7a4dd281ec66224f802093962d1d903d86b09560 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 5 Mar 2012 13:15:09 -0800 Subject: 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 Cc: Vivek Goyal Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 21 --------------------- 1 file changed, 21 deletions(-) (limited to 'block/cfq-iosched.c') 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; } -- cgit v1.2.3-59-g8ed1b