[PATCH 2/7] block: remove hctx->sched_debugfs_dir

[Ming Lei <ming.lei@xxxxxxxxxx>]

For each hctx, its sched debugfs path is fixed, which can be queried from
its parent dentry directly, so it isn't necessary to cache it in hctx
instance because it isn't used in fast path.

Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 block/blk-mq-debugfs.c | 31 ++++++++++++++++++++++++-------
 include/linux/blk-mq.h |  5 -----
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 16260bba4d11..3abb38ea2577 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -634,7 +634,7 @@ void blk_mq_debugfs_register(struct request_queue *q)
 	/* Similarly, blk_mq_init_hctx() couldn't do this previously. */
 	queue_for_each_hw_ctx(q, hctx, i) {
 		blk_mq_debugfs_register_hctx(q, hctx);
-		if (q->elevator && !hctx->sched_debugfs_dir)
+		if (q->elevator)
 			blk_mq_debugfs_register_sched_hctx(q, hctx);
 	}
 
@@ -657,6 +657,19 @@ static __must_check struct dentry *blk_mq_get_hctx_entry(
 	return debugfs_lookup(name, hctx->queue->debugfs_dir);
 }
 
+static __must_check struct dentry *blk_mq_get_hctx_sched_entry(
+		struct blk_mq_hw_ctx *hctx)
+{
+	struct dentry *hctx_dir = blk_mq_get_hctx_entry(hctx);
+	struct dentry *sched_dir = NULL;
+
+	if (hctx_dir) {
+		sched_dir = debugfs_lookup("sched", hctx_dir);
+		dput(hctx_dir);
+	}
+	return sched_dir;
+}
+
 static void blk_mq_debugfs_register_ctx(struct blk_mq_hw_ctx *hctx,
 					struct blk_mq_ctx *ctx)
 {
@@ -708,7 +721,6 @@ void blk_mq_debugfs_unregister_hctx(struct blk_mq_hw_ctx *hctx)
 		return;
 
 	debugfs_remove_recursive(hctx_dir);
-	hctx->sched_debugfs_dir = NULL;
 	dput(hctx_dir);
 }
 
@@ -805,6 +817,7 @@ void blk_mq_debugfs_register_sched_hctx(struct request_queue *q,
 {
 	struct dentry *hctx_dir = blk_mq_get_hctx_entry(hctx);
 	struct elevator_type *e = q->elevator->type;
+	struct dentry *sched_dir;
 
 	lockdep_assert_held(&q->debugfs_mutex);
 
@@ -819,19 +832,23 @@ void blk_mq_debugfs_register_sched_hctx(struct request_queue *q,
 	if (!e->hctx_debugfs_attrs)
 		goto exit;
 
-	hctx->sched_debugfs_dir = debugfs_create_dir("sched", hctx_dir);
-	debugfs_create_files(hctx->sched_debugfs_dir, hctx,
-			     e->hctx_debugfs_attrs);
+	sched_dir = debugfs_create_dir("sched", hctx_dir);
+	debugfs_create_files(sched_dir, hctx, e->hctx_debugfs_attrs);
 exit:
 	dput(hctx_dir);
 }
 
 void blk_mq_debugfs_unregister_sched_hctx(struct blk_mq_hw_ctx *hctx)
 {
+	struct dentry *sched_dir;
+
 	lockdep_assert_held(&hctx->queue->debugfs_mutex);
 
 	if (!hctx->queue->debugfs_dir)
 		return;
-	debugfs_remove_recursive(hctx->sched_debugfs_dir);
-	hctx->sched_debugfs_dir = NULL;
+	sched_dir = blk_mq_get_hctx_sched_entry(hctx);
+	if (sched_dir) {
+		debugfs_remove_recursive(sched_dir);
+		dput(sched_dir);
+	}
 }
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 8c8682491403..965aeea75ddd 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -426,11 +426,6 @@ struct blk_mq_hw_ctx {
 	/** @kobj: Kernel object for sysfs. */
 	struct kobject		kobj;
 
-#ifdef CONFIG_BLK_DEBUG_FS
-	/** @sched_debugfs_dir:	debugfs directory for the scheduler. */
-	struct dentry		*sched_debugfs_dir;
-#endif
-
 	/**
 	 * @hctx_list: if this hctx is not in use, this is an entry in
 	 * q->unused_hctx_list.
-- 
2.47.0