[PATCH 5.5 012/120] RDMA/umem: Fix ib_umem_find_best_pgsz()

[Greg Kroah-Hartman]

From: Artemy Kovalyov <artemyko@xxxxxxxxxxxx>

commit 36798d5ae1af62e830c5e045b2e41ce038690c61 upstream.

Except for the last entry, the ending iova alignment sets the maximum
possible page size as the low bits of the iova must be zero when starting
the next chunk.

Fixes: 4a35339958f1 ("RDMA/umem: Add API to find best driver supported page size in an MR")
Link: https://lore.kernel.org/r/20200128135612.174820-1-leon@xxxxxxxxxx
Signed-off-by: Artemy Kovalyov <artemyko@xxxxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Tested-by: Gal Pressman <galpress@xxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/core/umem.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -166,10 +166,13 @@ unsigned long ib_umem_find_best_pgsz(str
 		 * for any address.
 		 */
 		mask |= (sg_dma_address(sg) + pgoff) ^ va;
-		if (i && i != (umem->nmap - 1))
-			/* restrict by length as well for interior SGEs */
-			mask |= sg_dma_len(sg);
 		va += sg_dma_len(sg) - pgoff;
+		/* Except for the last entry, the ending iova alignment sets
+		 * the maximum possible page size as the low bits of the iova
+		 * must be zero when starting the next chunk.
+		 */
+		if (i != (umem->nmap - 1))
+			mask |= va;
 		pgoff = 0;
 	}
 	best_pg_bit = rdma_find_pg_bit(mask, pgsz_bitmap);