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authorTejun Heo <tj@kernel.org>2012-03-06 01:15:22 +0400
committerJens Axboe <axboe@kernel.dk>2012-03-07 00:27:24 +0400
commitc875f4d0250a1f070fa26087a73bdd8f54c48100 (patch)
tree4ed2bae2fc48e54ac712d28eaaae8217c8064c1d /block/blk-cgroup.h
parent9f13ef678efd977487fc0c2e489f17c9a8c67a3e (diff)
downloadlinux-c875f4d0250a1f070fa26087a73bdd8f54c48100.tar.xz
blkcg: drop unnecessary RCU locking
Now that blkg additions / removals are always done under both q and blkcg locks, the only places RCU locking is necessary are blkg_lookup[_create]() for lookup w/o blkcg lock. This patch drops unncessary RCU locking replacing it with plain blkcg locking as necessary. * blkiocg_pre_destroy() already perform proper locking and don't need RCU. Dropped. * blkio_read_blkg_stats() now uses blkcg->lock instead of RCU read lock. This isn't a hot path. * Now unnecessary synchronize_rcu() from queue exit paths removed. This makes q->nr_blkgs unnecessary. Dropped. * RCU annotation on blkg->q removed. -v2: Vivek pointed out that blkg_lookup_create() still needs to be called under rcu_read_lock(). Updated. -v3: After the update, stats_lock locking in blkio_read_blkg_stats() shouldn't be using _irq variant as it otherwise ends up enabling irq while blkcg->lock is locked. Fixed. 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-cgroup.h')
-rw-r--r--block/blk-cgroup.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index df73040a6a5f..66eaefefcbd2 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -176,8 +176,8 @@ struct blkg_policy_data {
};
struct blkio_group {
- /* Pointer to the associated request_queue, RCU protected */
- struct request_queue __rcu *q;
+ /* Pointer to the associated request_queue */
+ struct request_queue *q;
struct list_head q_node;
struct hlist_node blkcg_node;
struct blkio_cgroup *blkcg;