IB/srp: Introduce the 'register_always' kernel module parameter

Add a kernel module parameter that enables memory registration also for SG-lists
that can be processed without memory registration. This makes it easier for kernel
developers to test the memory registration code.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index c2e0ad399213..77ba96553b27 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -66,6 +66,7 @@ static unsigned int srp_sg_tablesize;
 static unsigned int cmd_sg_entries;
 static unsigned int indirect_sg_entries;
 static bool allow_ext_sg;
+static bool register_always;
 static int topspin_workarounds = 1;
 
 module_param(srp_sg_tablesize, uint, 0444);
@@ -87,6 +88,10 @@ module_param(topspin_workarounds, int, 0444);
 MODULE_PARM_DESC(topspin_workarounds,
                  "Enable workarounds for Topspin/Cisco SRP target bugs if != 0");
 
+module_param(register_always, bool, 0444);
+MODULE_PARM_DESC(register_always,
+                 "Use memory registration even for contiguous memory regions");
+
 static struct kernel_param_ops srp_tmo_ops;
 
 static int srp_reconnect_delay = 10;
@@ -956,7 +961,7 @@ static int srp_finish_mapping(struct srp_map_state *state,
         if (state->npages == 0)
                 return 0;
 
-        if (state->npages == 1)
+        if (state->npages == 1 && !register_always)
                 srp_map_desc(state, state->base_dma_addr, state->fmr_len,
                              target->rkey);
         else
@@ -1138,7 +1143,7 @@ static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_target_port *target,
         fmt = SRP_DATA_DESC_DIRECT;
         len = sizeof (struct srp_cmd) + sizeof (struct srp_direct_buf);
 
-        if (count == 1) {
+        if (count == 1 && !register_always) {
                 /*
                  * The midlayer only generated a single gather/scatter
                  * entry, or DMA mapping coalesced everything to a