target: Add/check max_write_same_len device attribute + update block limits VPD

This patch adds a new max_write_same_len device attribute for use with
WRITE_SAME w/ UNMAP=0 backend emulation.  This can be useful for
lowering the default backend value (IBLOCK uses 0xFFFF).

Also, update block limits VPD emulation code in spc_emulate_evpd_b0() to
report MAXIMUM WRITE SAME LENGTH, and enforce max_write_same_len during
sbc_parse() -> sbc_setup_write_same() CDB sanity checking for all emulated
WRITE_SAME w/ UNMAP=0 cases.

(Robert: Move max_write_same_len check in sbc_setup_write_same() to
         check both WRITE_SAME w/ UNMAP=1 and w/ UNMAP=0 cases)

Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Robert Elliott <Elliott@hp.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 5350f6e580f0..645d90ac6097 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -71,6 +71,8 @@
 #define DA_UNMAP_GRANULARITY_DEFAULT            0
 /* Default unmap_granularity_alignment */
 #define DA_UNMAP_GRANULARITY_ALIGNMENT_DEFAULT  0
+/* Default max_write_same_len, disabled by default */
+#define DA_MAX_WRITE_SAME_LEN                   0
 /* Default max transfer length */
 #define DA_FABRIC_MAX_SECTORS                   8192
 /* Emulation for Direct Page Out */
@@ -609,6 +611,7 @@ struct se_dev_attrib {
         u32             max_unmap_block_desc_count;
         u32             unmap_granularity;
         u32             unmap_granularity_alignment;
+        u32             max_write_same_len;
         struct se_device *da_dev;
         struct config_group da_group;
 };