block: move elevator tags into struct elevator_resources

This patch introduces a new structure, struct elevator_resources, to
group together all elevator-related resources that share the same
lifetime. As a first step, this change moves the elevator tag pointer
from struct elv_change_ctx into the new struct elevator_resources.

Additionally, rename blk_mq_alloc_sched_tags_batch() and
blk_mq_free_sched_tags_batch() to blk_mq_alloc_sched_res_batch() and
blk_mq_free_sched_res_batch(), respectively. Introduce two new wrapper
helpers, blk_mq_alloc_sched_res() and blk_mq_free_sched_res(), around
blk_mq_alloc_sched_tags() and blk_mq_free_sched_tags().

These changes pave the way for consolidating the allocation and freeing
of elevator-specific resources into common helper functions. This
refactoring improves encapsulation and prepares the code for future
extensions, allowing additional elevator-specific data to be added to
struct elevator_resources without cluttering struct elv_change_ctx.

Subsequent patches will extend struct elevator_resources to include
other elevator-related data.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Yu Kuai <yukuai@fnnas.com>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 16 insertions, 15 deletions

diff --git a/block/elevator.c b/block/elevator.c
index cd7bdff205c8..cbec292a4af5 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -580,7 +580,7 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
 	}
 
 	if (new_e) {
-		ret = blk_mq_init_sched(q, new_e, ctx->et);
+		ret = blk_mq_init_sched(q, new_e, &ctx->res);
 		if (ret)
 			goto out_unfreeze;
 		ctx->new = q->elevator;
@@ -604,7 +604,8 @@ out_unfreeze:
 	return ret;
 }
 
-static void elv_exit_and_release(struct request_queue *q)
+static void elv_exit_and_release(struct elv_change_ctx *ctx,
+		struct request_queue *q)
 {
 	struct elevator_queue *e;
 	unsigned memflags;
@@ -616,7 +617,7 @@ static void elv_exit_and_release(struct request_queue *q)
 	mutex_unlock(&q->elevator_lock);
 	blk_mq_unfreeze_queue(q, memflags);
 	if (e) {
-		blk_mq_free_sched_tags(e->et, q->tag_set);
+		blk_mq_free_sched_res(&ctx->res, q->tag_set);
 		kobject_put(&e->kobj);
 	}
 }
@@ -627,11 +628,12 @@ static int elevator_change_done(struct request_queue *q,
 	int ret = 0;
 
 	if (ctx->old) {
+		struct elevator_resources res = {.et = ctx->old->et};
 		bool enable_wbt = test_bit(ELEVATOR_FLAG_ENABLE_WBT_ON_EXIT,
 				&ctx->old->flags);
 
 		elv_unregister_queue(q, ctx->old);
-		blk_mq_free_sched_tags(ctx->old->et, q->tag_set);
+		blk_mq_free_sched_res(&res, q->tag_set);
 		kobject_put(&ctx->old->kobj);
 		if (enable_wbt)
 			wbt_enable_default(q->disk);
@@ -639,7 +641,7 @@ static int elevator_change_done(struct request_queue *q,
 	if (ctx->new) {
 		ret = elv_register_queue(q, ctx->new, !ctx->no_uevent);
 		if (ret)
-			elv_exit_and_release(q);
+			elv_exit_and_release(ctx, q);
 	}
 	return ret;
 }
@@ -656,10 +658,9 @@ static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)
 	lockdep_assert_held(&set->update_nr_hwq_lock);
 
 	if (strncmp(ctx->name, "none", 4)) {
-		ctx->et = blk_mq_alloc_sched_tags(set, set->nr_hw_queues,
-				blk_mq_default_nr_requests(set));
-		if (!ctx->et)
-			return -ENOMEM;
+		ret = blk_mq_alloc_sched_res(q, &ctx->res, set->nr_hw_queues);
+		if (ret)
+			return ret;
 	}
 
 	memflags = blk_mq_freeze_queue(q);
@@ -681,10 +682,10 @@ static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)
 	if (!ret)
 		ret = elevator_change_done(q, ctx);
 	/*
-	 * Free sched tags if it's allocated but we couldn't switch elevator.
+	 * Free sched resource if it's allocated but we couldn't switch elevator.
 	 */
-	if (ctx->et && !ctx->new)
-		blk_mq_free_sched_tags(ctx->et, set);
+	if (!ctx->new)
+		blk_mq_free_sched_res(&ctx->res, set);
 
 	return ret;
 }
@@ -711,10 +712,10 @@ void elv_update_nr_hw_queues(struct request_queue *q,
 	if (!ret)
 		WARN_ON_ONCE(elevator_change_done(q, ctx));
 	/*
-	 * Free sched tags if it's allocated but we couldn't switch elevator.
+	 * Free sched resource if it's allocated but we couldn't switch elevator.
 	 */
-	if (ctx->et && !ctx->new)
-		blk_mq_free_sched_tags(ctx->et, set);
+	if (!ctx->new)
+		blk_mq_free_sched_res(&ctx->res, set);
 }
 
 /*