linux-kernel - [PATCH 4.7 159/186] IB/core, RDMA RW API: Do not exceed QP SGE send limit

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Date:	Thu, 18 Aug 2016 15:59:36 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Bart Van Assche <bart.vanassche@...disk.com>,
	Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>,
	Steve Wise <swise@...ngridcomputing.com>,
	Parav Pandit <pandit.parav@...il.com>,
	Nicholas Bellinger <nab@...ux-iscsi.org>,
	Laurence Oberman <loberman@...hat.com>,
	Doug Ledford <dledford@...hat.com>
Subject: [PATCH 4.7 159/186] IB/core, RDMA RW API: Do not exceed QP SGE send limit

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche@...disk.com>

commit 632bc3f65081dd1e2e5394a9161580a0f78e8839 upstream.

Compute the SGE limit for RDMA READ and WRITE requests in
ib_create_qp(). Use that limit in the RDMA RW API implementation.

Signed-off-by: Bart Van Assche <bart.vanassche@...disk.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Sagi Grimberg <sagi@...mberg.me>
Cc: Steve Wise <swise@...ngridcomputing.com>
Cc: Parav Pandit <pandit.parav@...il.com>
Cc: Nicholas Bellinger <nab@...ux-iscsi.org>
Cc: Laurence Oberman <loberman@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Doug Ledford <dledford@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/infiniband/core/rw.c    |   10 ++--------
 drivers/infiniband/core/verbs.c |    9 +++++++++
 include/rdma/ib_verbs.h         |    6 ++++++
 3 files changed, 17 insertions(+), 8 deletions(-)

--- a/drivers/infiniband/core/rw.c
+++ b/drivers/infiniband/core/rw.c
@@ -58,13 +58,6 @@ static inline bool rdma_rw_io_needs_mr(s
 	return false;
 }
 
-static inline u32 rdma_rw_max_sge(struct ib_device *dev,
-		enum dma_data_direction dir)
-{
-	return dir == DMA_TO_DEVICE ?
-		dev->attrs.max_sge : dev->attrs.max_sge_rd;
-}
-
 static inline u32 rdma_rw_fr_page_list_len(struct ib_device *dev)
 {
 	/* arbitrary limit to avoid allocating gigantic resources */
@@ -186,7 +179,8 @@ static int rdma_rw_init_map_wrs(struct r
 		u64 remote_addr, u32 rkey, enum dma_data_direction dir)
 {
 	struct ib_device *dev = qp->pd->device;
-	u32 max_sge = rdma_rw_max_sge(dev, dir);
+	u32 max_sge = dir == DMA_TO_DEVICE ? qp->max_write_sge :
+		      qp->max_read_sge;
 	struct ib_sge *sge;
 	u32 total_len = 0, i, j;
 
--- a/drivers/infiniband/core/verbs.c
+++ b/drivers/infiniband/core/verbs.c
@@ -814,6 +814,15 @@ struct ib_qp *ib_create_qp(struct ib_pd
 		}
 	}
 
+	/*
+	 * Note: all hw drivers guarantee that max_send_sge is lower than
+	 * the device RDMA WRITE SGE limit but not all hw drivers ensure that
+	 * max_send_sge <= max_sge_rd.
+	 */
+	qp->max_write_sge = qp_init_attr->cap.max_send_sge;
+	qp->max_read_sge = min_t(u32, qp_init_attr->cap.max_send_sge,
+				 device->attrs.max_sge_rd);
+
 	return qp;
 }
 EXPORT_SYMBOL(ib_create_qp);
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1428,6 +1428,10 @@ struct ib_srq {
 	} ext;
 };
 
+/*
+ * @max_write_sge: Maximum SGE elements per RDMA WRITE request.
+ * @max_read_sge:  Maximum SGE elements per RDMA READ request.
+ */
 struct ib_qp {
 	struct ib_device       *device;
 	struct ib_pd	       *pd;
@@ -1449,6 +1453,8 @@ struct ib_qp {
 	void                  (*event_handler)(struct ib_event *, void *);
 	void		       *qp_context;
 	u32			qp_num;
+	u32			max_write_sge;
+	u32			max_read_sge;
 	enum ib_qp_type		qp_type;
 };