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authorTejun Heo <tj@kernel.org>2012-03-05 13:15:09 -0800
committerJens Axboe <axboe@kernel.dk>2012-03-06 21:27:22 +0100
commit7a4dd281ec66224f802093962d1d903d86b09560 (patch)
treec38c5c40464d4d7eb429cc14348a435176832ef2 /block/blk-throttle.c
parent4bfd482e73b30284cb21e10834ce729fa81aa256 (diff)
downloadop-kernel-dev-7a4dd281ec66224f802093962d1d903d86b09560.zip
op-kernel-dev-7a4dd281ec66224f802093962d1d903d86b09560.tar.gz
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/blk-throttle.c')
-rw-r--r--block/blk-throttle.c51
1 files changed, 2 insertions, 49 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 791b107..52a4293 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));
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