blkcg: make blkg_conf_prep() take @pol and return with queue lock held

Add @pol to blkg_conf_prep() and let it return with queue lock held
(to be released by blkg_conf_finish()).  Note that @pol isn't used
yet.

This is to prepare for per-queue policy activation and doesn't cause
any visible difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 10 insertions, 7 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 2d4d7d6d9ae9..f6581a090b9d 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -464,17 +464,19 @@ EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
 /**
  * blkg_conf_prep - parse and prepare for per-blkg config update
  * @blkcg: target block cgroup
+ * @pol: target policy
  * @input: input string
  * @ctx: blkg_conf_ctx to be filled
  *
  * Parse per-blkg config update from @input and initialize @ctx with the
  * result.  @ctx->blkg points to the blkg to be updated and @ctx->v the new
- * value.  This function returns with RCU read locked and must be paired
- * with blkg_conf_finish().
+ * value.  This function returns with RCU read lock and queue lock held and
+ * must be paired with blkg_conf_finish().
  */
-int blkg_conf_prep(struct blkio_cgroup *blkcg, const char *input,
+int blkg_conf_prep(struct blkio_cgroup *blkcg,
+                   const struct blkio_policy_type *pol, const char *input,
                    struct blkg_conf_ctx *ctx)
-        __acquires(rcu)
+        __acquires(rcu) __acquires(disk->queue->queue_lock)
 {
         struct gendisk *disk;
         struct blkio_group *blkg;
@@ -490,14 +492,14 @@ int blkg_conf_prep(struct blkio_cgroup *blkcg, const char *input,
                 return -EINVAL;
 
         rcu_read_lock();
-
         spin_lock_irq(disk->queue->queue_lock);
+
         blkg = blkg_lookup_create(blkcg, disk->queue, false);
-        spin_unlock_irq(disk->queue->queue_lock);
 
         if (IS_ERR(blkg)) {
                 ret = PTR_ERR(blkg);
                 rcu_read_unlock();
+                spin_unlock_irq(disk->queue->queue_lock);
                 put_disk(disk);
                 /*
                  * If queue was bypassing, we should retry.  Do so after a
@@ -527,8 +529,9 @@ EXPORT_SYMBOL_GPL(blkg_conf_prep);
  * with blkg_conf_prep().
  */
 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
-        __releases(rcu)
+        __releases(ctx->disk->queue->queue_lock) __releases(rcu)
 {
+        spin_unlock_irq(ctx->disk->queue->queue_lock);
         rcu_read_unlock();
         put_disk(ctx->disk);
 }