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

[Kashyap Desai <kashyap.desai@broadcom.com>]

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> > 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.

John - I have included your comments. Below is add-on patch which handles
all your comment except one.
Below is just compiled (not tested patch). Please let me know if you like to
handle "scsi_init_hctx" in this patch or shall we do it as a separate patch
(out of this patch series.) ?


--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1769,9 +1769,7 @@ static void scsi_mq_exit_request(struct blk_mq_tag_set
*set, struct request *rq,

 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;
+       struct Scsi_Host *shost = hctx->driver_data;

        if (shost->hostt->mq_poll)
                return shost->hostt->mq_poll(shost, hctx->queue_num);
@@ -1779,6 +1777,14 @@ static int scsi_mq_poll(struct blk_mq_hw_ctx *hctx)
        return 0;
 }

+static int scsi_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
+                         unsigned int hctx_idx)
+{
+       struct Scsi_Host *shost = data;
+       hctx->driver_data = shost;
+       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);
@@ -1846,6 +1852,7 @@ 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,
+       .init_hctx      = scsi_init_hctx,
        .poll           = scsi_mq_poll,
 };

@@ -1875,6 +1882,7 @@ static const struct blk_mq_ops scsi_mq_ops = {
        .cleanup_rq     = scsi_cleanup_rq,
        .busy           = scsi_mq_lld_busy,
        .map_queues     = scsi_map_queues,
+       .init_hctx      = scsi_init_hctx,
        .poll           = scsi_mq_poll,
 };

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 5844374a85b1..cc30df96f5f7 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -9,8 +9,8 @@
 #include <linux/types.h>
 #include <linux/timer.h>
 #include <linux/scatterlist.h>
-#include <scsi/scsi_host.h>
 #include <scsi/scsi_device.h>
+#include <scsi/scsi_host.h>
 #include <scsi/scsi_request.h>

 struct Scsi_Host;
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 905ee6b00c55..a0cda0f66b84 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -274,7 +274,7 @@ struct scsi_host_template {
         * 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.
+        * Return value: Number of completed entries found.
         *
         * Status: OPTIONAL
         */

>
> > +
> > +	if (shost->hostt->mq_poll)
>
> to avoid this check, could we reject if .mq_poll is not set and
> HCTX_TYPE_POLL is?

Is this urgent or shall we improve later ? I am not able to figure out how
you want to manage this ? Can you explain little bit ?

Kashyap

>
> > +		return shost->hostt->mq_poll(shost, hctx->queue_num);
> > +
> > +	return 0;
> > +}

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