block: remove dead elevator code

This removes a bunch of core and elevator related code. On the core
front, we remove anything related to queue running, draining,
initialization, plugging, and congestions. We also kill anything
related to request allocation, merging, retrieval, and completion.

Remove any checking for single queue IO schedulers, as they no
longer exist. This means we can also delete a bunch of code related
to request issue, adding, completion, etc - and all the SQ related
ops and helpers.

Also kill the load_default_modules(), as all that did was provide
for a way to load the default single queue elevator.

Tested-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 9 insertions, 27 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 1b82ccfde3fe..d4b1b84ba8ca 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -68,7 +68,7 @@ queue_requests_store(struct request_queue *q, const char *page, size_t count)
         unsigned long nr;
         int ret, err;
 
-        if (!q->request_fn && !q->mq_ops)
+        if (!q->mq_ops)
                 return -EINVAL;
 
         ret = queue_var_store(&nr, page, count);
@@ -78,11 +78,7 @@ queue_requests_store(struct request_queue *q, const char *page, size_t count)
         if (nr < BLKDEV_MIN_RQ)
                 nr = BLKDEV_MIN_RQ;
 
-        if (q->request_fn)
-                err = blk_update_nr_requests(q, nr);
-        else
-                err = blk_mq_update_nr_requests(q, nr);
-
+        err = blk_mq_update_nr_requests(q, nr);
         if (err)
                 return err;
 
@@ -463,20 +459,14 @@ static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
          * ends up either enabling or disabling wbt completely. We can't
          * have IO inflight if that happens.
          */
-        if (q->mq_ops) {
-                blk_mq_freeze_queue(q);
-                blk_mq_quiesce_queue(q);
-        } else
-                blk_queue_bypass_start(q);
+        blk_mq_freeze_queue(q);
+        blk_mq_quiesce_queue(q);
 
         wbt_set_min_lat(q, val);
         wbt_update_limits(q);
 
-        if (q->mq_ops) {
-                blk_mq_unquiesce_queue(q);
-                blk_mq_unfreeze_queue(q);
-        } else
-                blk_queue_bypass_end(q);
+        blk_mq_unquiesce_queue(q);
+        blk_mq_unfreeze_queue(q);
 
         return count;
 }
@@ -847,17 +837,10 @@ static void __blk_release_queue(struct work_struct *work)
 
         blk_free_queue_stats(q->stats);
 
-        blk_exit_rl(q, &q->root_rl);
-
         blk_queue_free_zone_bitmaps(q);
 
-        if (!q->mq_ops) {
-                if (q->exit_rq_fn)
-                        q->exit_rq_fn(q, q->fq->flush_rq);
-                blk_free_flush_queue(q->fq);
-        } else {
+        if (q->mq_ops)
                 blk_mq_release(q);
-        }
 
         blk_trace_shutdown(q);
 
@@ -920,7 +903,6 @@ int blk_register_queue(struct gendisk *disk)
         if (!blk_queue_init_done(q)) {
                 queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q);
                 percpu_ref_switch_to_percpu(&q->q_usage_counter);
-                blk_queue_bypass_end(q);
         }
 
         ret = blk_trace_init_sysfs(dev);
@@ -947,7 +929,7 @@ int blk_register_queue(struct gendisk *disk)
 
         blk_throtl_register_queue(q);
 
-        if (q->request_fn || (q->mq_ops && q->elevator)) {
+        if ((q->mq_ops && q->elevator)) {
                 ret = elv_register_queue(q);
                 if (ret) {
                         mutex_unlock(&q->sysfs_lock);
@@ -1005,7 +987,7 @@ void blk_unregister_queue(struct gendisk *disk)
         blk_trace_remove_sysfs(disk_to_dev(disk));
 
         mutex_lock(&q->sysfs_lock);
-        if (q->request_fn || (q->mq_ops && q->elevator))
+        if (q->mq_ops && q->elevator)
                 elv_unregister_queue(q);
         mutex_unlock(&q->sysfs_lock);