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authorTejun Heo <tj@kernel.org>2012-03-05 13:15:00 -0800
committerJens Axboe <axboe@kernel.dk>2012-03-06 21:27:22 +0100
commit72e06c255181537d0b3e1f657a9ed81655d745b1 (patch)
treeeb656df2ad23a7709b4e9fe58f1dabdc32be9ae9 /block/cfq-iosched.c
parent6ecf23afab13c39d3bb0e2d826d0984b0dd53733 (diff)
blkcg: shoot down blkio_groups on elevator switch
Elevator switch may involve changes to blkcg policies. Implement shoot down of blkio_groups. Combined with the previous bypass updates, the end goal is updating blkcg core such that it can ensure that blkcg's being affected become quiescent and don't have any per-blkg data hanging around before commencing any policy updates. Until queues are made aware of the policies that applies to them, as an interim step, all per-policy blkg data will be shot down. * blk-throtl doesn't need this change as it can't be disabled for a live queue; however, update it anyway as the scheduled blkg unification requires this behavior change. This means that blk-throtl configuration will be unnecessarily lost over elevator switch. This oddity will be removed after blkcg learns to associate individual policies with request_queues. * blk-throtl dosen't shoot down root_tg. This is to ease transition. Unified blkg will always have persistent root group and not shooting down root_tg for now eases transition to that point by avoiding having to update td->root_tg and is safe as blk-throtl can never be disabled -v2: Vivek pointed out that group list is not guaranteed to be empty on return from clear function if it raced cgroup removal and lost. Fix it by waiting a bit and retrying. This kludge will soon be removed once locking is updated such that blkg is never in limbo state between blkcg and request_queue locks. blk-throtl no longer shoots down root_tg to avoid breaking td->root_tg. Also, Nest queue_lock inside blkio_list_lock not the other way around to avoid introduce possible deadlock via blkcg lock. -v3: blkcg_clear_queue() repositioned and renamed to blkg_destroy_all() to increase consistency with later changes. cfq_clear_queue() updated to check q->elevator before dereferencing it to avoid NULL dereference on not fully initialized queues (used by later change). 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.c20
1 files changed, 19 insertions, 1 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 72680a6715f..61693d3404d 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1225,10 +1225,11 @@ static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
cfq_put_cfqg(cfqg);
}
-static void cfq_release_cfq_groups(struct cfq_data *cfqd)
+static bool cfq_release_cfq_groups(struct cfq_data *cfqd)
{
struct hlist_node *pos, *n;
struct cfq_group *cfqg;
+ bool empty = true;
hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
/*
@@ -1238,7 +1239,10 @@ static void cfq_release_cfq_groups(struct cfq_data *cfqd)
*/
if (!cfq_blkiocg_del_blkio_group(&cfqg->blkg))
cfq_destroy_cfqg(cfqd, cfqg);
+ else
+ empty = false;
}
+ return empty;
}
/*
@@ -1265,6 +1269,19 @@ static void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
+static struct elevator_type iosched_cfq;
+
+static bool cfq_clear_queue(struct request_queue *q)
+{
+ lockdep_assert_held(q->queue_lock);
+
+ /* shoot down blkgs iff the current elevator is cfq */
+ if (!q->elevator || q->elevator->type != &iosched_cfq)
+ return true;
+
+ return cfq_release_cfq_groups(q->elevator->elevator_data);
+}
+
#else /* GROUP_IOSCHED */
static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd)
{
@@ -3875,6 +3892,7 @@ static struct elevator_type iosched_cfq = {
static struct blkio_policy_type blkio_policy_cfq = {
.ops = {
.blkio_unlink_group_fn = cfq_unlink_blkio_group,
+ .blkio_clear_queue_fn = cfq_clear_queue,
.blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
},
.plid = BLKIO_POLICY_PROP,