IB/iser: New receive buffer posting logic

Currently, the recv buffer posting logic is based on the transactional
nature of iSER which allows for posting a buffer before sending a PDU.
Change this to post only when the number of outstanding recv buffers
is below a water mark and in a batched manner, thus simplifying and
optimizing the data path.  Use a pre-allocated ring of recv buffers
instead of allocating from kmem cache.  A special treatment is given
to the login response buffer whose size must be 8K unlike the size of
buffers used for any other purpose which is 128 bytes.

Signed-off-by: Or Gerlitz <ogerlitz@voltaire.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 33 insertions, 7 deletions

diff --git a/drivers/infiniband/ulp/iser/iscsi_iser.h b/drivers/infiniband/ulp/iser/iscsi_iser.h
index e8dfdcfa1daf..83effb610594 100644
--- a/drivers/infiniband/ulp/iser/iscsi_iser.h
+++ b/drivers/infiniband/ulp/iser/iscsi_iser.h
@@ -102,9 +102,9 @@
 #define ISER_MAX_TX_MISC_PDUS           6 /* NOOP_OUT(2), TEXT(1),         *
                                            * SCSI_TMFUNC(2), LOGOUT(1) */
 
-#define ISER_QP_MAX_RECV_DTOS           (ISCSI_DEF_XMIT_CMDS_MAX + \
-                                        ISER_MAX_RX_MISC_PDUS    +  \
-                                        ISER_MAX_TX_MISC_PDUS)
+#define ISER_QP_MAX_RECV_DTOS           (ISCSI_DEF_XMIT_CMDS_MAX)
+
+#define ISER_MIN_POSTED_RX              (ISCSI_DEF_XMIT_CMDS_MAX >> 2)
 
 /* the max TX (send) WR supported by the iSER QP is defined by                 *
  * max_send_wr = T * (1 + D) + C ; D is how many inflight dataouts we expect   *
@@ -132,6 +132,12 @@ struct iser_hdr {
         __be64  read_va;
 } __attribute__((packed));
 
+/* Constant PDU lengths calculations */
+#define ISER_HEADERS_LEN  (sizeof(struct iser_hdr) + sizeof(struct iscsi_hdr))
+
+#define ISER_RECV_DATA_SEG_LEN  128
+#define ISER_RX_PAYLOAD_SIZE    (ISER_HEADERS_LEN + ISER_RECV_DATA_SEG_LEN)
+#define ISER_RX_LOGIN_SIZE      (ISER_HEADERS_LEN + ISCSI_DEF_MAX_RECV_SEG_LEN)
 
 /* Length of an object name string */
 #define ISER_OBJECT_NAME_SIZE               64
@@ -212,7 +218,6 @@ struct iser_dto {
 };
 
 enum iser_desc_type {
-        ISCSI_RX,
         ISCSI_TX_CONTROL ,
         ISCSI_TX_SCSI_COMMAND,
         ISCSI_TX_DATAOUT
@@ -228,6 +233,17 @@ struct iser_desc {
         struct iser_dto              dto;
 };
 
+#define ISER_RX_PAD_SIZE        (256 - (ISER_RX_PAYLOAD_SIZE + \
+                                        sizeof(u64) + sizeof(struct ib_sge)))
+struct iser_rx_desc {
+        struct iser_hdr              iser_header;
+        struct iscsi_hdr             iscsi_header;
+        char                         data[ISER_RECV_DATA_SEG_LEN];
+        u64                          dma_addr;
+        struct ib_sge                rx_sg;
+        char                         pad[ISER_RX_PAD_SIZE];
+} __attribute__((packed));
+
 struct iser_device {
         struct ib_device             *ib_device;
         struct ib_pd                 *pd;
@@ -256,6 +272,12 @@ struct iser_conn {
         struct iser_page_vec         *page_vec;     /* represents SG to fmr maps*
                                                      * maps serialized as tx is*/
         struct list_head             conn_list;       /* entry in ig conn list */
+
+        char                         *login_buf;
+        u64                          login_dma;
+        unsigned int                 rx_desc_head;
+        struct iser_rx_desc          *rx_descs;
+        struct ib_recv_wr            rx_wr[ISER_MIN_POSTED_RX];
 };
 
 struct iscsi_iser_conn {
@@ -319,8 +341,9 @@ void iser_conn_put(struct iser_conn *ib_conn);
 
 void iser_conn_terminate(struct iser_conn *ib_conn);
 
-void iser_rcv_completion(struct iser_desc *desc,
-                         unsigned long    dto_xfer_len);
+void iser_rcv_completion(struct iser_rx_desc *desc,
+                         unsigned long    dto_xfer_len,
+                        struct iser_conn *ib_conn);
 
 void iser_snd_completion(struct iser_desc *desc);
 
@@ -332,6 +355,8 @@ void iser_dto_buffs_release(struct iser_dto *dto);
 
 int  iser_regd_buff_release(struct iser_regd_buf *regd_buf);
 
+void iser_free_rx_descriptors(struct iser_conn *ib_conn);
+
 void iser_reg_single(struct iser_device      *device,
                      struct iser_regd_buf    *regd_buf,
                      enum dma_data_direction direction);
@@ -353,7 +378,8 @@ int  iser_reg_page_vec(struct iser_conn     *ib_conn,
 
 void iser_unreg_mem(struct iser_mem_reg *mem_reg);
 
-int  iser_post_recv(struct iser_desc *rx_desc);
+int  iser_post_recvl(struct iser_conn *ib_conn);
+int  iser_post_recvm(struct iser_conn *ib_conn, int count);
 int  iser_post_send(struct iser_desc *tx_desc);
 
 int iser_conn_state_comp(struct iser_conn *ib_conn,