IB/srp: allow lockless work posting

Only one CPU at a time will own an RX IU, so using the address of the IU
as the work request cookie allows us to avoid taking a lock. We can
similarly prepare the TX path for lockless posting by moving the free TX
IUs to a list. This also removes the requirement that the queue sizes be
a power of 2.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
[ broken out, small cleanups, and modified to avoid needing an extra field
  in the IU by David Dillow]
Signed-off-by: David Dillow <dillowda@ornl.gov>

1 files changed, 2 insertions, 5 deletions

diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
index f8b689a644b7..41ecb46adf15 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -59,10 +59,8 @@ enum {
 
         SRP_RQ_SHIFT            = 6,
         SRP_RQ_SIZE             = 1 << SRP_RQ_SHIFT,
-        SRP_RQ_MASK             = SRP_RQ_SIZE - 1,
 
         SRP_SQ_SIZE             = SRP_RQ_SIZE,
-        SRP_SQ_MASK             = SRP_SQ_SIZE - 1,
         SRP_RSP_SQ_SIZE         = 1,
         SRP_REQ_SQ_SIZE         = SRP_SQ_SIZE - SRP_RSP_SQ_SIZE,
         SRP_TSK_MGMT_SQ_SIZE    = 1,
@@ -144,11 +142,9 @@ struct srp_target_port {
 
         int                     zero_req_lim;
 
-        unsigned                rx_head;
         struct srp_iu          *rx_ring[SRP_RQ_SIZE];
 
-        unsigned                tx_head;
-        unsigned                tx_tail;
+        struct list_head        free_tx;
         struct srp_iu          *tx_ring[SRP_SQ_SIZE];
 
         struct list_head        free_reqs;
@@ -168,6 +164,7 @@ struct srp_target_port {
 };
 
 struct srp_iu {
+        struct list_head        list;
         u64                     dma;
         void                   *buf;
         size_t                  size;