blk-mq: remove REQ_END

Pass an explicit parameter for the last request in a batch to ->queue_rq
instead of using a request flag.  Besides being a cleaner and non-stateful
interface this is also required for the next patch, which fixes the blk-mq
I/O submission code to not start a time too early.

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

7 files changed, 14 insertions, 25 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index e743d28620b2..32b4797f4186 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -384,7 +384,7 @@ void blk_mq_complete_request(struct request *rq)
 }
 EXPORT_SYMBOL(blk_mq_complete_request);
 
-static void blk_mq_start_request(struct request *rq, bool last)
+static void blk_mq_start_request(struct request *rq)
 {
         struct request_queue *q = rq->q;
 
@@ -421,16 +421,6 @@ static void blk_mq_start_request(struct request *rq, bool last)
                  */
                 rq->nr_phys_segments++;
         }
-
-        /*
-         * Flag the last request in the series so that drivers know when IO
-         * should be kicked off, if they don't do it on a per-request basis.
-         *
-         * Note: the flag isn't the only condition drivers should do kick off.
-         * If drive is busy, the last request might not have the bit set.
-         */
-        if (last)
-                rq->cmd_flags |= REQ_END;
 }
 
 static void __blk_mq_requeue_request(struct request *rq)
@@ -440,8 +430,6 @@ static void __blk_mq_requeue_request(struct request *rq)
         trace_block_rq_requeue(q, rq);
         clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
 
-        rq->cmd_flags &= ~REQ_END;
-
         if (q->dma_drain_size && blk_rq_bytes(rq))
                 rq->nr_phys_segments--;
 }
@@ -755,9 +743,9 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
                 rq = list_first_entry(&rq_list, struct request, queuelist);
                 list_del_init(&rq->queuelist);
 
-                blk_mq_start_request(rq, list_empty(&rq_list));
+                blk_mq_start_request(rq);
 
-                ret = q->mq_ops->queue_rq(hctx, rq);
+                ret = q->mq_ops->queue_rq(hctx, rq, list_empty(&rq_list));
                 switch (ret) {
                 case BLK_MQ_RQ_QUEUE_OK:
                         queued++;
@@ -1198,14 +1186,14 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
                 int ret;
 
                 blk_mq_bio_to_request(rq, bio);
-                blk_mq_start_request(rq, true);
+                blk_mq_start_request(rq);
 
                 /*
                  * For OK queue, we are done. For error, kill it. Any other
                  * error (busy), just add it to our list as we previously
                  * would have done
                  */
-                ret = q->mq_ops->queue_rq(data.hctx, rq);
+                ret = q->mq_ops->queue_rq(data.hctx, rq, true);
                 if (ret == BLK_MQ_RQ_QUEUE_OK)
                         goto done;
                 else {
diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index 5c8e7fe07745..0e2084f37c67 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -3775,7 +3775,8 @@ static bool mtip_check_unal_depth(struct blk_mq_hw_ctx *hctx,
         return false;
 }
 
-static int mtip_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq)
+static int mtip_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq,
+                bool last)
 {
         int ret;
 
diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 00d469c7f9f7..c5b7315c2c13 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -313,7 +313,8 @@ static void null_request_fn(struct request_queue *q)
         }
 }
 
-static int null_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq)
+static int null_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq,
+                bool last)
 {
         struct nullb_cmd *cmd = blk_mq_rq_to_pdu(rq);
 
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 0a581400de0f..13756e016797 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -164,14 +164,14 @@ static void virtblk_done(struct virtqueue *vq)
         spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
 }
 
-static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
+static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req,
+                bool last)
 {
         struct virtio_blk *vblk = hctx->queue->queuedata;
         struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
         unsigned long flags;
         unsigned int num;
         int qid = hctx->queue_num;
-        const bool last = (req->cmd_flags & REQ_END) != 0;
         int err;
         bool notify = false;
 
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 1f2bae475cb7..f1df41168391 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1855,7 +1855,8 @@ static void scsi_mq_done(struct scsi_cmnd *cmd)
         blk_mq_complete_request(cmd->request);
 }
 
-static int scsi_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
+static int scsi_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req,
+                bool last)
 {
         struct request_queue *q = req->q;
         struct scsi_device *sdev = q->queuedata;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index a1e31f274fcd..9c4e306a9217 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -77,7 +77,7 @@ struct blk_mq_tag_set {
         struct list_head        tag_list;
 };
 
-typedef int (queue_rq_fn)(struct blk_mq_hw_ctx *, struct request *);
+typedef int (queue_rq_fn)(struct blk_mq_hw_ctx *, struct request *, bool);
 typedef struct blk_mq_hw_ctx *(map_queue_fn)(struct request_queue *, const int);
 typedef int (init_hctx_fn)(struct blk_mq_hw_ctx *, void *, unsigned int);
 typedef void (exit_hctx_fn)(struct blk_mq_hw_ctx *, unsigned int);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 66c2167f04a9..bb7d66460e7a 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -188,7 +188,6 @@ enum rq_flag_bits {
         __REQ_MIXED_MERGE,      /* merge of different types, fail separately */
         __REQ_KERNEL,           /* direct IO to kernel pages */
         __REQ_PM,               /* runtime pm request */
-        __REQ_END,              /* last of chain of requests */
         __REQ_HASHED,           /* on IO scheduler merge hash */
         __REQ_MQ_INFLIGHT,      /* track inflight for MQ */
         __REQ_NR_BITS,          /* stops here */
@@ -242,7 +241,6 @@ enum rq_flag_bits {
 #define REQ_SECURE              (1ULL << __REQ_SECURE)
 #define REQ_KERNEL              (1ULL << __REQ_KERNEL)
 #define REQ_PM                  (1ULL << __REQ_PM)
-#define REQ_END                 (1ULL << __REQ_END)
 #define REQ_HASHED              (1ULL << __REQ_HASHED)
 #define REQ_MQ_INFLIGHT         (1ULL << __REQ_MQ_INFLIGHT)