blk-mq-sched: unify request prepare methods

This patch makes sure we always allocate requests in the core blk-mq
code and use a common prepare_request method to initialize them for
both mq I/O schedulers.  For Kyber and additional limit_depth method
is added that is called before allocating the request.

Also because none of the intializations can really fail the new method
does not return an error - instead the bfq finish method is hardened
to deal with the no-IOC case.

Last but not least this removes the abuse of RQF_QUEUE by the blk-mq
scheduling code as RQF_ELFPRIV is all that is needed now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 12 insertions, 7 deletions

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index f037b005faa1..60d32700f104 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4292,8 +4292,14 @@ static void bfq_put_rq_priv_body(struct bfq_queue *bfqq)
 
 static void bfq_finish_request(struct request *rq)
 {
-        struct bfq_queue *bfqq = RQ_BFQQ(rq);
-        struct bfq_data *bfqd = bfqq->bfqd;
+        struct bfq_queue *bfqq;
+        struct bfq_data *bfqd;
+
+        if (!rq->elv.icq)
+                return;
+
+        bfqq = RQ_BFQQ(rq);
+        bfqd = bfqq->bfqd;
 
         if (rq->rq_flags & RQF_STARTED)
                 bfqg_stats_update_completion(bfqq_group(bfqq),
@@ -4394,9 +4400,9 @@ static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd,
 /*
  * Allocate bfq data structures associated with this request.
  */
-static int bfq_get_rq_private(struct request_queue *q, struct request *rq,
-                              struct bio *bio)
+static void bfq_prepare_request(struct request *rq, struct bio *bio)
 {
+        struct request_queue *q = rq->q;
         struct bfq_data *bfqd = q->elevator->elevator_data;
         struct bfq_io_cq *bic;
         const int is_sync = rq_is_sync(rq);
@@ -4405,7 +4411,7 @@ static int bfq_get_rq_private(struct request_queue *q, struct request *rq,
         bool split = false;
 
         if (!rq->elv.icq)
-                return 1;
+                return;
         bic = icq_to_bic(rq->elv.icq);
 
         spin_lock_irq(&bfqd->lock);
@@ -4466,7 +4472,6 @@ static int bfq_get_rq_private(struct request_queue *q, struct request *rq,
                 bfq_handle_burst(bfqd, bfqq);
 
         spin_unlock_irq(&bfqd->lock);
-        return 0;
 }
 
 static void bfq_idle_slice_timer_body(struct bfq_queue *bfqq)
@@ -4945,7 +4950,7 @@ static struct elv_fs_entry bfq_attrs[] = {
 
 static struct elevator_type iosched_bfq_mq = {
         .ops.mq = {
-                .get_rq_priv            = bfq_get_rq_private,
+                .prepare_request        = bfq_prepare_request,
                 .finish_request         = bfq_finish_request,
                 .exit_icq               = bfq_exit_icq,
                 .insert_requests        = bfq_insert_requests,