target: Pass through I/O topology for block backstores

In addition to block size (already implemented), passing through
alignment offset, logical-to-phys block exponent, I/O granularity and
optimal I/O length will allow initiators to properly handle layout on
LUNs with 4K block sizes.

Tested with various weird values via scsi_debug module.

One thing to look at with this patch is the new block limits values --
instead of granularity 1 optimal 8192, Lio will now be returning whatever
the block device says, which may affect performance.

Signed-off-by: Andy Grover <agrover@redhat.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/target/target_core_spc.c b/drivers/target/target_core_spc.c
index 074539558a54..f89a86f29ee3 100644
--- a/drivers/target/target_core_spc.c
+++ b/drivers/target/target_core_spc.c
@@ -452,6 +452,7 @@ spc_emulate_evpd_b0(struct se_cmd *cmd, unsigned char *buf)
         struct se_device *dev = cmd->se_dev;
         u32 max_sectors;
         int have_tp = 0;
+        int opt, min;
 
         /*
          * Following spc3r22 section 6.5.3 Block Limits VPD page, when
@@ -475,7 +476,10 @@ spc_emulate_evpd_b0(struct se_cmd *cmd, unsigned char *buf)
         /*
          * Set OPTIMAL TRANSFER LENGTH GRANULARITY
          */
-        put_unaligned_be16(1, &buf[6]);
+        if (dev->transport->get_io_min && (min = dev->transport->get_io_min(dev)))
+                put_unaligned_be16(min / dev->dev_attrib.block_size, &buf[6]);
+        else
+                put_unaligned_be16(1, &buf[6]);
 
         /*
          * Set MAXIMUM TRANSFER LENGTH
@@ -487,7 +491,10 @@ spc_emulate_evpd_b0(struct se_cmd *cmd, unsigned char *buf)
         /*
          * Set OPTIMAL TRANSFER LENGTH
          */
-        put_unaligned_be32(dev->dev_attrib.optimal_sectors, &buf[12]);
+        if (dev->transport->get_io_opt && (opt = dev->transport->get_io_opt(dev)))
+                put_unaligned_be32(opt / dev->dev_attrib.block_size, &buf[12]);
+        else
+                put_unaligned_be32(dev->dev_attrib.optimal_sectors, &buf[12]);
 
         /*
          * Exit now if we don't support TP.