[PATCHv2 1/2] IB/iser: Fix sg_tablesize calculation

[PATCHv2 1/2] IB/iser: Fix sg_tablesize calculation

[Max Gurtovoy]

For devices that can register page list that is bigger than
USHRT_MAX, we actually take the wrong value for sg_tablesize.
E.g: for CX4 max_fast_reg_page_list_len is 65536 (bigger than USHRT_MAX)
so we set sg_tablesize to 0 by mistake. Therefore, each IO that is
bigger than 4k splitted to "< 4k" chunks that cause performance degredation.
Remove wrong sg_tablesize assignment, and use the value that was set during
address resolution handler with the needed casting.

Fixes: 911f4331bc87 ("IB/mlx5: Expose correct max_fast_reg_page_list_len")
Cc: <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org> # v4.5+
Signed-off-by: Max Gurtovoy <maxg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
Changes since v1:
 - update "Fixes" statement
 - use sg_tablesize assignment from iser_calc_scsi_params()
 - add patch 2/2 to remove unneeded variable
---
 drivers/infiniband/ulp/iser/iscsi_iser.c |    7 -------
 1 files changed, 0 insertions(+), 7 deletions(-)

diff --git a/drivers/infiniband/ulp/iser/iscsi_iser.c b/drivers/infiniband/ulp/iser/iscsi_iser.c
index 9104e6b..1c91187 100644
--- a/drivers/infiniband/ulp/iser/iscsi_iser.c
+++ b/drivers/infiniband/ulp/iser/iscsi_iser.c
@@ -651,13 +651,6 @@ static void iscsi_iser_cleanup_task(struct iscsi_task *task)
 						   SHOST_DIX_GUARD_CRC);
 		}
 
-		/*
-		 * Limit the sg_tablesize and max_sectors based on the device
-		 * max fastreg page list length.
-		 */
-		shost->sg_tablesize = min_t(unsigned short, shost->sg_tablesize,
-			ib_conn->device->ib_device->attrs.max_fast_reg_page_list_len);
-
 		if (iscsi_host_add(shost,
 				   ib_conn->device->ib_device->dma_device)) {
 			mutex_unlock(&iser_conn->state_mutex);
-- 
1.7.1

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[PATCHv2 2/2] IB/iser: remove unused variable from iser_conn struct

[Max Gurtovoy]

max_sectors calculation was fixed in commit:
9c674815d346 ("IB/iser: Fix max_sectors calculation").
Thus, iser_conn variable scsi_max_sectors is not needed anymore.

Signed-off-by: Max Gurtovoy <maxg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
 drivers/infiniband/ulp/iser/iscsi_iser.c |    4 ++++
 drivers/infiniband/ulp/iser/iscsi_iser.h |    2 --
 drivers/infiniband/ulp/iser/iser_verbs.c |   13 +------------
 3 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/drivers/infiniband/ulp/iser/iscsi_iser.c b/drivers/infiniband/ulp/iser/iscsi_iser.c
index 1c91187..e71af71 100644
--- a/drivers/infiniband/ulp/iser/iscsi_iser.c
+++ b/drivers/infiniband/ulp/iser/iscsi_iser.c
@@ -672,6 +672,10 @@ static void iscsi_iser_cleanup_task(struct iscsi_task *task)
 	max_fr_sectors = ((shost->sg_tablesize - 1) * PAGE_SIZE) >> 9;
 	shost->max_sectors = min(iser_max_sectors, max_fr_sectors);
 
+	iser_dbg("iser_conn %p, sg_tablesize %u, max_sectors %u\n",
+		 iser_conn, shost->sg_tablesize,
+		 shost->max_sectors);
+
 	if (cmds_max > max_cmds) {
 		iser_info("cmds_max changed from %u to %u\n",
 			  cmds_max, max_cmds);
diff --git a/drivers/infiniband/ulp/iser/iscsi_iser.h b/drivers/infiniband/ulp/iser/iscsi_iser.h
index 0be6a7c..9d0b22a 100644
--- a/drivers/infiniband/ulp/iser/iscsi_iser.h
+++ b/drivers/infiniband/ulp/iser/iscsi_iser.h
@@ -496,7 +496,6 @@ struct ib_conn {
  * @rx_descs:         rx buffers array (cyclic buffer)
  * @num_rx_descs:     number of rx descriptors
  * @scsi_sg_tablesize: scsi host sg_tablesize
- * @scsi_max_sectors: scsi host max sectors
  */
 struct iser_conn {
 	struct ib_conn		     ib_conn;
@@ -519,7 +518,6 @@ struct iser_conn {
 	struct iser_rx_desc	     *rx_descs;
 	u32                          num_rx_descs;
 	unsigned short               scsi_sg_tablesize;
-	unsigned int                 scsi_max_sectors;
 	bool			     snd_w_inv;
 };
 
diff --git a/drivers/infiniband/ulp/iser/iser_verbs.c b/drivers/infiniband/ulp/iser/iser_verbs.c
index 8ae7a3b..6a9d1cb 100644
--- a/drivers/infiniband/ulp/iser/iser_verbs.c
+++ b/drivers/infiniband/ulp/iser/iser_verbs.c
@@ -707,18 +707,7 @@ static void iser_connect_error(struct rdma_cm_id *cma_id)
 	sup_sg_tablesize = min_t(unsigned, ISCSI_ISER_MAX_SG_TABLESIZE,
 				 device->ib_device->attrs.max_fast_reg_page_list_len);
 
-	if (sg_tablesize > sup_sg_tablesize) {
-		sg_tablesize = sup_sg_tablesize;
-		iser_conn->scsi_max_sectors = sg_tablesize * SIZE_4K / 512;
-	} else {
-		iser_conn->scsi_max_sectors = max_sectors;
-	}
-
-	iser_conn->scsi_sg_tablesize = sg_tablesize;
-
-	iser_dbg("iser_conn %p, sg_tablesize %u, max_sectors %u\n",
-		 iser_conn, iser_conn->scsi_sg_tablesize,
-		 iser_conn->scsi_max_sectors);
+	iser_conn->scsi_sg_tablesize = min(sg_tablesize, sup_sg_tablesize);
 }
 
 /**
-- 
1.7.1

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Re: [PATCHv2 1/2] IB/iser: Fix sg_tablesize calculation

[Sagi Grimberg]

> For devices that can register page list that is bigger than
> USHRT_MAX, we actually take the wrong value for sg_tablesize.
> E.g: for CX4 max_fast_reg_page_list_len is 65536 (bigger than USHRT_MAX)
> so we set sg_tablesize to 0 by mistake. Therefore, each IO that is
> bigger than 4k splitted to "< 4k" chunks that cause performance degredation.
> Remove wrong sg_tablesize assignment, and use the value that was set during
> address resolution handler with the needed casting.
>
> Fixes: 911f4331bc87 ("IB/mlx5: Expose correct max_fast_reg_page_list_len")

That's not correct, the patch was a fix which exposed a bug in iser
that was broken anyway. Let's remove it.

Other than that, looks good,

Reviewed-by: Sagi Grimberg <sagi-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org>
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Re: [PATCHv2 2/2] IB/iser: remove unused variable from iser_conn struct

[Sagi Grimberg]

Looks good,

Reviewed-by: Sagi Grimberg <sagi-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org>
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RE: [PATCHv2 2/2] IB/iser: remove unused variable from iser_conn struct

[Steve Wise]

> Looks good,
> 
> Reviewed-by: Sagi Grimberg <sagi-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org>

Chelsio will test these 2 out asap over cxgb4 and report back.

Steve.

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