RDMA/srpt: Add support for immediate data

Modify allocation of the non-SRQ receive queues such that immediate
data is aligned on a 512 byte boundary. That alignment is necessary
to pass the immediate data without copying to the block layer. When
receiving an SRP_CMD with immediate data, postpone the ib_post_recv()
call until target_execute_cmd() has finished. See also
srpt_release_cmd().

Cc: Sergey Gorenko <sergeygo@mellanox.com>
Cc: Max Gurtovoy <maxg@mellanox.com>
Cc: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/ulp/srpt/ib_srpt.h

@@ -120,11 +120,18 @@ enum {
 	MAX_SRPT_RDMA_SIZE = 1U << 24,
 	MAX_SRPT_RSP_SIZE = 1024,
 
+	SRP_MAX_ADD_CDB_LEN = 16,
+	SRP_MAX_IMM_DATA_OFFSET = 80,
+	SRP_MAX_IMM_DATA = 8 * 1024,
 	MIN_MAX_REQ_SIZE = 996,
-	DEFAULT_MAX_REQ_SIZE
-		= sizeof(struct srp_cmd)/*48*/
-		+ sizeof(struct srp_indirect_buf)/*20*/
-		+ 128 * sizeof(struct srp_direct_buf)/*16*/,
+	DEFAULT_MAX_REQ_SIZE_1 = sizeof(struct srp_cmd)/*48*/ +
+				 SRP_MAX_ADD_CDB_LEN +
+				 sizeof(struct srp_indirect_buf)/*20*/ +
+				 128 * sizeof(struct srp_direct_buf)/*16*/,
+	DEFAULT_MAX_REQ_SIZE_2 = SRP_MAX_IMM_DATA_OFFSET +
+				 sizeof(struct srp_imm_buf) + SRP_MAX_IMM_DATA,
+	DEFAULT_MAX_REQ_SIZE = DEFAULT_MAX_REQ_SIZE_1 > DEFAULT_MAX_REQ_SIZE_2 ?
+			       DEFAULT_MAX_REQ_SIZE_1 : DEFAULT_MAX_REQ_SIZE_2,
 
 	MIN_MAX_RSP_SIZE = sizeof(struct srp_rsp)/*36*/ + 4,
 	DEFAULT_MAX_RSP_SIZE = 256, /* leaves 220 bytes for sense data */
@@ -161,12 +168,14 @@ enum srpt_command_state {
  * @cqe:   Completion queue element.
  * @buf:   Pointer to the buffer.
  * @dma:   DMA address of the buffer.
+ * @offset: Offset of the first byte in @buf and @dma that is actually used.
  * @index: Index of the I/O context in its ioctx_ring array.
  */
 struct srpt_ioctx {
 	struct ib_cqe		cqe;
 	void			*buf;
 	dma_addr_t		dma;
+	uint32_t		offset;
 	uint32_t		index;
 };
 
@@ -174,10 +183,12 @@ struct srpt_ioctx {
  * struct srpt_recv_ioctx - SRPT receive I/O context
  * @ioctx:     See above.
  * @wait_list: Node for insertion in srpt_rdma_ch.cmd_wait_list.
+ * @byte_len:  Number of bytes in @ioctx.buf.
  */
 struct srpt_recv_ioctx {
 	struct srpt_ioctx	ioctx;
 	struct list_head	wait_list;
+	int			byte_len;
 };
 
 struct srpt_rw_ctx {
@@ -190,8 +201,11 @@ struct srpt_rw_ctx {
  * struct srpt_send_ioctx - SRPT send I/O context
  * @ioctx:       See above.
  * @ch:          Channel pointer.
+ * @recv_ioctx:  Receive I/O context associated with this send I/O context.
+ *		 Only used for processing immediate data.
  * @s_rw_ctx:    @rw_ctxs points here if only a single rw_ctx is needed.
  * @rw_ctxs:     RDMA read/write contexts.
+ * @imm_sg:      Scatterlist for immediate data.
  * @rdma_cqe:    RDMA completion queue element.
  * @free_list:   Node in srpt_rdma_ch.free_list.
  * @state:       I/O context state.
@@ -205,10 +219,13 @@ struct srpt_rw_ctx {
 struct srpt_send_ioctx {
 	struct srpt_ioctx	ioctx;
 	struct srpt_rdma_ch	*ch;
+	struct srpt_recv_ioctx	*recv_ioctx;
 
 	struct srpt_rw_ctx	s_rw_ctx;
 	struct srpt_rw_ctx	*rw_ctxs;
 
+	struct scatterlist	imm_sg;
+
 	struct ib_cqe		rdma_cqe;
 	struct list_head	free_list;
 	enum srpt_command_state	state;
@@ -258,12 +275,15 @@ enum rdma_ch_state {
  * @req_lim:       request limit: maximum number of requests that may be sent
  *                 by the initiator without having received a response.
  * @req_lim_delta: Number of credits not yet sent back to the initiator.
+ * @imm_data_offset: Offset from start of SRP_CMD for immediate data.
  * @spinlock:      Protects free_list and state.
  * @free_list:     Head of list with free send I/O contexts.
  * @state:         channel state. See also enum rdma_ch_state.
  * @using_rdma_cm: Whether the RDMA/CM or IB/CM is used for this channel.
  * @processing_wait_list: Whether or not cmd_wait_list is being processed.
+ * @rsp_buf_cache: kmem_cache for @ioctx_ring.
  * @ioctx_ring:    Send ring.
+ * @req_buf_cache: kmem_cache for @ioctx_recv_ring.
  * @ioctx_recv_ring: Receive I/O context ring.
  * @list:          Node in srpt_nexus.ch_list.
  * @cmd_wait_list: List of SCSI commands that arrived before the RTU event. This
@@ -296,10 +316,13 @@ struct srpt_rdma_ch {
 	int			max_ti_iu_len;
 	atomic_t		req_lim;
 	atomic_t		req_lim_delta;
+	u16			imm_data_offset;
 	spinlock_t		spinlock;
 	struct list_head	free_list;
 	enum rdma_ch_state	state;
+	struct kmem_cache	*rsp_buf_cache;
 	struct srpt_send_ioctx	**ioctx_ring;
+	struct kmem_cache	*req_buf_cache;
 	struct srpt_recv_ioctx	**ioctx_recv_ring;
 	struct list_head	list;
 	struct list_head	cmd_wait_list;
@@ -394,6 +417,7 @@ struct srpt_port {
  * @srq_size:      SRQ size.
  * @sdev_mutex:	   Serializes use_srq changes.
  * @use_srq:       Whether or not to use SRQ.
+ * @req_buf_cache: kmem_cache for @ioctx_ring buffers.
  * @ioctx_ring:    Per-HCA SRQ.
  * @event_handler: Per-HCA asynchronous IB event handler.
  * @list:          Node in srpt_dev_list.
@@ -408,6 +432,7 @@ struct srpt_device {
 	int			srq_size;
 	struct mutex		sdev_mutex;
 	bool			use_srq;
+	struct kmem_cache	*req_buf_cache;
 	struct srpt_recv_ioctx	**ioctx_ring;
 	struct ib_event_handler	event_handler;
 	struct list_head	list;