queue-5.15/rdma-rtrs-srv-fix-sg-mapping.patch

From 61acd55ea3f61f15290a54bcb07027a04df8a4e4 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Wed, 7 Jan 2026 17:15:08 +0100
Subject: RDMA/rtrs-srv: fix SG mapping

From: Roman Penyaev <r.peniaev@gmail.com>

[ Upstream commit 83835f7c07b523c7ca2a5ad0a511670b5810539e ]

This fixes the following error on the server side:

   RTRS server session allocation failed: -EINVAL

caused by the caller of the `ib_dma_map_sg()`, which does not expect
less mapped entries, than requested, which is in the order of things
and can be easily reproduced on the machine with enabled IOMMU.

The fix is to treat any positive number of mapped sg entries as a
successful mapping and cache DMA addresses by traversing modified
SG table.

Fixes: 9cb837480424 ("RDMA/rtrs: server: main functionality")
Signed-off-by: Roman Penyaev <r.peniaev@gmail.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Grzegorz Prajsner <grzegorz.prajsner@ionos.com>
Link: https://patch.msgid.link/20260107161517.56357-2-haris.iqbal@ionos.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/infiniband/ulp/rtrs/rtrs-srv.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.c b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
index b5f3cbf0fd79c..8ccac2bce5123 100644
--- a/drivers/infiniband/ulp/rtrs/rtrs-srv.c
+++ b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
@@ -597,7 +597,7 @@ static int map_cont_bufs(struct rtrs_srv_path *srv_path)
 	     srv_path->mrs_num++) {
 		struct rtrs_srv_mr *srv_mr = &srv_path->mrs[srv_path->mrs_num];
 		struct scatterlist *s;
-		int nr, nr_sgt, chunks;
+		int nr, nr_sgt, chunks, ind;
 
 		sgt = &srv_mr->sgt;
 		chunks = chunks_per_mr * srv_path->mrs_num;
@@ -627,7 +627,7 @@ static int map_cont_bufs(struct rtrs_srv_path *srv_path)
 		}
 		nr = ib_map_mr_sg(mr, sgt->sgl, nr_sgt,
 				  NULL, max_chunk_size);
-		if (nr != nr_sgt) {
+		if (nr < nr_sgt) {
 			err = nr < 0 ? nr : -EINVAL;
 			goto dereg_mr;
 		}
@@ -643,9 +643,24 @@ static int map_cont_bufs(struct rtrs_srv_path *srv_path)
 				goto dereg_mr;
 			}
 		}
-		/* Eventually dma addr for each chunk can be cached */
-		for_each_sg(sgt->sgl, s, nr_sgt, i)
-			srv_path->dma_addr[chunks + i] = sg_dma_address(s);
+
+		/*
+		 * Cache DMA addresses by traversing sg entries.  If
+		 * regions were merged, an inner loop is required to
+		 * populate the DMA address array by traversing larger
+		 * regions.
+		 */
+		ind = chunks;
+		for_each_sg(sgt->sgl, s, nr_sgt, i) {
+			unsigned int dma_len = sg_dma_len(s);
+			u64 dma_addr = sg_dma_address(s);
+			u64 dma_addr_end = dma_addr + dma_len;
+
+			do {
+				srv_path->dma_addr[ind++] = dma_addr;
+				dma_addr += max_chunk_size;
+			} while (dma_addr < dma_addr_end);
+		}
 
 		ib_update_fast_reg_key(mr, ib_inc_rkey(mr->rkey));
 		srv_mr->mr = mr;
-- 
2.51.0