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/blk-throttle.c | 51 ++------------------------------------------------- 1 file changed, 2 insertions(+), 49 deletions(-) (limited to 'block/blk-throttle.c') diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 791b10719e43..52a429397d3b 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -212,50 +212,12 @@ static struct blkio_group *throtl_alloc_blkio_group(struct request_queue *q, return &tg->blkg; } -static void -__throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg) -{ - struct backing_dev_info *bdi = &td->queue->backing_dev_info; - unsigned int major, minor; - - if (!tg || tg->blkg.dev) - return; - - /* - * Fill in device details for a group which might not have been - * filled at group creation time as queue was being instantiated - * and driver had not attached a device yet - */ - if (bdi->dev && dev_name(bdi->dev)) { - sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); - tg->blkg.dev = MKDEV(major, minor); - } -} - -/* - * Should be called with without queue lock held. Here queue lock will be - * taken rarely. It will be taken only once during life time of a group - * if need be - */ -static void -throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg) -{ - if (!tg || tg->blkg.dev) - return; - - spin_lock_irq(td->queue->queue_lock); - __throtl_tg_fill_dev_details(td, tg); - spin_unlock_irq(td->queue->queue_lock); -} - static void throtl_link_blkio_group(struct request_queue *q, struct blkio_group *blkg) { struct throtl_data *td = q->td; struct throtl_grp *tg = tg_of_blkg(blkg); - __throtl_tg_fill_dev_details(td, tg); - hlist_add_head(&tg->tg_node, &td->tg_list); td->nr_undestroyed_grps++; } @@ -263,20 +225,14 @@ static void throtl_link_blkio_group(struct request_queue *q, static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td, struct blkio_cgroup *blkcg) { - struct throtl_grp *tg = NULL; - /* * This is the common case when there are no blkio cgroups. * Avoid lookup in this case */ if (blkcg == &blkio_root_cgroup) - tg = td->root_tg; - else - tg = tg_of_blkg(blkg_lookup(blkcg, td->queue, - BLKIO_POLICY_THROTL)); + return td->root_tg; - __throtl_tg_fill_dev_details(td, tg); - return tg; + return tg_of_blkg(blkg_lookup(blkcg, td->queue, BLKIO_POLICY_THROTL)); } static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td, @@ -303,7 +259,6 @@ static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td, tg = td->root_tg; } - __throtl_tg_fill_dev_details(td, tg); return tg; } @@ -1090,8 +1045,6 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio) blkcg = task_blkio_cgroup(current); tg = throtl_lookup_tg(td, blkcg); if (tg) { - throtl_tg_fill_dev_details(td, tg); - if (tg_no_rule_group(tg, rw)) { blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, rw_is_sync(bio->bi_rw)); -- cgit v1.2.3