target: Add WRITE_SAME (10) parsing and refactor passthrough checks

This patch adds initial WRITE_SAME (10) w/ UNMAP=1 support following updates in
sbcr26 to allow UNMAP=1 for the non 16 + 32 byte CDB case.  It also refactors
current pSCSI passthrough passthrough checks into target_check_write_same_discard()
ahead of UNMAP=0 w/ write payload support into target_core_iblock.c.

This includes the support for handling WRITE_SAME in transport_emulate_control_cdb(),
and converts target_emulate_write_same to accept num_blocks directly for
WRITE_SAME, WRITE_SAME_16 and WRITE_SAME_32.

Reported-by: Eric Seppanen <eric@purestorage.com>
Cc: Roland Dreier <roland@purestorage.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@risingtidesystems.com>

1 files changed, 16 insertions, 12 deletions

diff --git a/drivers/target/target_core_cdb.c b/drivers/target/target_core_cdb.c
index d095408dbd5f..4c1d3a98e894 100644
--- a/drivers/target/target_core_cdb.c
+++ b/drivers/target/target_core_cdb.c
@@ -1090,24 +1090,17 @@ err:
  * Note this is not used for TCM/pSCSI passthrough
  */
 static int
-target_emulate_write_same(struct se_task *task, int write_same32)
+target_emulate_write_same(struct se_task *task, u32 num_blocks)
 {
         struct se_cmd *cmd = task->task_se_cmd;
         struct se_device *dev = cmd->se_dev;
         sector_t range;
         sector_t lba = cmd->t_task_lba;
-        unsigned int num_blocks;
         int ret;
         /*
-         * Extract num_blocks from the WRITE_SAME_* CDB.  Then use the explict
-         * range when non zero is supplied, otherwise calculate the remaining
-         * range based on ->get_blocks() - starting LBA.
+         * Use the explicit range when non zero is supplied, otherwise calculate
+         * the remaining range based on ->get_blocks() - starting LBA.
          */
-        if (write_same32)
-                num_blocks = get_unaligned_be32(&cmd->t_task_cdb[28]);
-        else
-                num_blocks = get_unaligned_be32(&cmd->t_task_cdb[10]);
-
         if (num_blocks != 0)
                 range = num_blocks;
         else
@@ -1170,13 +1163,23 @@ transport_emulate_control_cdb(struct se_task *task)
                 }
                 ret = target_emulate_unmap(task);
                 break;
+        case WRITE_SAME:
+                if (!dev->transport->do_discard) {
+                        pr_err("WRITE_SAME emulation not supported"
+                                        " for: %s\n", dev->transport->name);
+                        return PYX_TRANSPORT_UNKNOWN_SAM_OPCODE;
+                }
+                ret = target_emulate_write_same(task,
+                                get_unaligned_be16(&cmd->t_task_cdb[7]));
+                break;
         case WRITE_SAME_16:
                 if (!dev->transport->do_discard) {
                         pr_err("WRITE_SAME_16 emulation not supported"
                                         " for: %s\n", dev->transport->name);
                         return PYX_TRANSPORT_UNKNOWN_SAM_OPCODE;
                 }
-                ret = target_emulate_write_same(task, 0);
+                ret = target_emulate_write_same(task,
+                                get_unaligned_be32(&cmd->t_task_cdb[10]));
                 break;
         case VARIABLE_LENGTH_CMD:
                 service_action =
@@ -1189,7 +1192,8 @@ transport_emulate_control_cdb(struct se_task *task)
                                         dev->transport->name);
                                 return PYX_TRANSPORT_UNKNOWN_SAM_OPCODE;
                         }
-                        ret = target_emulate_write_same(task, 1);
+                        ret = target_emulate_write_same(task,
+                                get_unaligned_be32(&cmd->t_task_cdb[28]));
                         break;
                 default:
                         pr_err("Unsupported VARIABLE_LENGTH_CMD SA:"