Re: [PATCH v1 1/3] add io_uring with IOPOLL support in scsi layer

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On 15/10/2020 14:36, Kashyap Desai wrote:
io_uring with IOPOLL is not currently supported in scsi mid layer.
Outside of that everything else should work and no extra support in the driver is needed.
Currently io_uring with IOPOLL support is only available in block layer.
This patch is to extend support of mq_poll in scsi layer. >
Signed-off-by: Kashyap Desai <kashyap.desai@xxxxxxxxxxxx>
Cc: sumit.saxena@xxxxxxxxxxxx
Cc: chandrakanth.patil@xxxxxxxxxxxx
Cc: linux-block@xxxxxxxxxxxxxxx

---
  drivers/scsi/scsi_lib.c  | 16 ++++++++++++++++
  include/scsi/scsi_cmnd.h |  1 +
  include/scsi/scsi_host.h | 11 +++++++++++
  3 files changed, 28 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 72b12102f777..5a3c383a2bb3 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1766,6 +1766,19 @@ static void scsi_mq_exit_request(struct blk_mq_tag_set *set, struct request *rq,
  			       cmd->sense_buffer);
  }
+
+static int scsi_mq_poll(struct blk_mq_hw_ctx *hctx)
+{
+	struct request_queue *q = hctx->queue;
+	struct scsi_device *sdev = q->queuedata;
+	struct Scsi_Host *shost = sdev->host;

could we separately set hctx->driver_data = shost or similar for a quicker lookup? I don't see hctx->driver_data set for SCSI currently. Going through the scsi_device looks strange - I know that it is done in scsi_commit_rqs.

+
+	if (shost->hostt->mq_poll)

to avoid this check, could we reject if .mq_poll is not set and HCTX_TYPE_POLL is?

+		return shost->hostt->mq_poll(shost, hctx->queue_num);
+
+	return 0;
+}
+
  static int scsi_map_queues(struct blk_mq_tag_set *set)
  {
  	struct Scsi_Host *shost = container_of(set, struct Scsi_Host, tag_set);
@@ -1833,6 +1846,7 @@ static const struct blk_mq_ops scsi_mq_ops_no_commit = {
  	.cleanup_rq	= scsi_cleanup_rq,
  	.busy		= scsi_mq_lld_busy,
  	.map_queues	= scsi_map_queues,
+	.poll		= scsi_mq_poll,
  };
@@ -1861,6 +1875,7 @@ static const struct blk_mq_ops scsi_mq_ops = {
  	.cleanup_rq	= scsi_cleanup_rq,
  	.busy		= scsi_mq_lld_busy,
  	.map_queues	= scsi_map_queues,
+	.poll		= scsi_mq_poll,
  };
struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev)
@@ -1893,6 +1908,7 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
  	else
  		tag_set->ops = &scsi_mq_ops_no_commit;
  	tag_set->nr_hw_queues = shost->nr_hw_queues ? : 1;
+	tag_set->nr_maps = shost->nr_maps ? : 1;
  	tag_set->queue_depth = shost->can_queue;
  	tag_set->cmd_size = cmd_size;
  	tag_set->numa_node = NUMA_NO_NODE;
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index e76bac4d14c5..5844374a85b1 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -9,6 +9,7 @@
  #include <linux/types.h>
  #include <linux/timer.h>
  #include <linux/scatterlist.h>
+#include <scsi/scsi_host.h>

can we maintain alphabetic ordering?

  #include <scsi/scsi_device.h>
  #include <scsi/scsi_request.h>
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 701f178b20ae..905ee6b00c55 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -270,6 +270,16 @@ struct scsi_host_template {
  	 */
  	int (* map_queues)(struct Scsi_Host *shost);
+ /*
+	 * SCSI interface of blk_poll - poll for IO completions.
+	 * Possible interface only if scsi LLD expose multiple h/w queues.
+	 *
+	 * Return values: Number of completed entries found.

/s/values/value/

+	 *
+	 * Status: OPTIONAL
+	 */
+	int (* mq_poll)(struct Scsi_Host *shost, unsigned int queue_num);
+
  	/*
  	 * Check if scatterlists need to be padded for DMA draining.
  	 *
@@ -610,6 +620,7 @@ struct Scsi_Host {
  	 * the total queue depth is can_queue.
  	 */
  	unsigned nr_hw_queues;
+	unsigned nr_maps; >   	unsigned active_mode:2;
  	unsigned unchecked_isa_dma:1;




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