IB/iser: Support up to 8MB data transfer in a single command

iser support up to 512KB data transfer in a single scsi command.
This means that larger IOs will split to different request. While
iser can easily saturate FDR/EDR wires, some arrays are fine tuned
for 1MB (or larger) IO sizes, hence add an option to support larger
transfers (up to 8MB) if the device allows it.

Given that a few target implementations don't support data transfers
of more than 512KB by default and the fact that larger IO sizes require
more resources, we introduce a module parameter to determine the
maximum number of 512B sectors in a single scsi command.
Users that are interested in larger transfers can change this value given
that the target supports larger transfers.

At the moment, iser works in 4K pages granularity, In a later stage
we will get it to work with system page size instead.

IO operations that consists of N pages will need a page vector
of size N+1 in case the first SG element contains an offset. Given
that some devices allocates memory regions in powers of 2, this
means that allocating a region with N+1 pages, will result in
region resources allocation of the next power of 2. Since we don't
want that to happen, in case we are in the limit of IO size supported
and the first SG element has an offset, we align the SG list using a
bounce buffer (which is OK given that this is not likely to happen a lot).

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/drivers/infiniband/ulp/iser/iscsi_iser.h b/drivers/infiniband/ulp/iser/iscsi_iser.h
index e9ebe0b2263d..0bdd7e77e5db 100644
--- a/drivers/infiniband/ulp/iser/iscsi_iser.h
+++ b/drivers/infiniband/ulp/iser/iscsi_iser.h
@@ -98,8 +98,13 @@
 #define SHIFT_4K	12
 #define SIZE_4K	(1ULL << SHIFT_4K)
 #define MASK_4K	(~(SIZE_4K-1))
-					/* support up to 512KB in one RDMA */
-#define ISCSI_ISER_SG_TABLESIZE         (0x80000 >> SHIFT_4K)
+
+/* Default support is 512KB I/O size */
+#define ISER_DEF_MAX_SECTORS		1024
+#define ISCSI_ISER_DEF_SG_TABLESIZE	((ISER_DEF_MAX_SECTORS * 512) >> SHIFT_4K)
+/* Maximum support is 8MB I/O size */
+#define ISCSI_ISER_MAX_SG_TABLESIZE	((16384 * 512) >> SHIFT_4K)
+
 #define ISER_DEF_XMIT_CMDS_DEFAULT		512
 #if ISCSI_DEF_XMIT_CMDS_MAX > ISER_DEF_XMIT_CMDS_DEFAULT
 	#define ISER_DEF_XMIT_CMDS_MAX		ISCSI_DEF_XMIT_CMDS_MAX
@@ -504,6 +509,8 @@ struct ib_conn {
  * @rx_desc_head:     head of rx_descs cyclic buffer
  * @rx_descs:         rx buffers array (cyclic buffer)
  * @num_rx_descs:     number of rx descriptors
+ * @scsi_sg_tablesize: scsi host sg_tablesize
+ * @scsi_max_sectors: scsi host max sectors
  */
 struct iser_conn {
 	struct ib_conn		     ib_conn;
@@ -528,6 +535,8 @@ struct iser_conn {
 	unsigned int 		     rx_desc_head;
 	struct iser_rx_desc	     *rx_descs;
 	u32                          num_rx_descs;
+	unsigned short               scsi_sg_tablesize;
+	unsigned int                 scsi_max_sectors;
 };
 
 /**
@@ -583,6 +592,7 @@ extern struct iser_global ig;
 extern int iser_debug_level;
 extern bool iser_pi_enable;
 extern int iser_pi_guard;
+extern unsigned int iser_max_sectors;
 
 int iser_assign_reg_ops(struct iser_device *device);