target: Fix WRITE_SAME_[16,32] number of blocks=0 case

This patch fixes the handling of WRITE_SAME_[16,32] emulation where a
WRITE_SAME_* CDB with number of blocks=0 was being rejected by SCSI
expected data transfer length overflow checking in target core.

It changes both CDB cases in transport_generic_cmd_sequencer() to use
dev->se_sub_dev->se_dev_attrib.block_size to match what sg_write_same
is sending us with --num=0.  It also fixes target_emulate_write_same()
to properly determine the num_blocks with --num=0 case to determine the
remaining range for dev->transport->do_discard().

Reported-by: Chris Greiveldinger <chris.greiveldinger@rnanetworks.com>
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>

2 files changed, 32 insertions, 10 deletions

diff --git a/drivers/target/target_core_cdb.c b/drivers/target/target_core_cdb.c
index 95195d71810..8d5a0fc3a22 100644
--- a/drivers/target/target_core_cdb.c
+++ b/drivers/target/target_core_cdb.c
@@ -1008,18 +1008,30 @@ target_emulate_unmap(struct se_task *task)
  * Note this is not used for TCM/pSCSI passthrough
  */
 static int
-target_emulate_write_same(struct se_task *task)
+target_emulate_write_same(struct se_task *task, int write_same32)
 {
         struct se_cmd *cmd = task->task_se_cmd;
         struct se_device *dev = cmd->se_dev;
-        sector_t lba = cmd->t_task.t_task_lba;
-        unsigned int range;
+        sector_t range, lba = cmd->t_task.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.
+         */
+        if (write_same32)
+                num_blocks = get_unaligned_be32(&cmd->t_task.t_task_cdb[28]);
+        else
+                num_blocks = get_unaligned_be32(&cmd->t_task.t_task_cdb[10]);
 
-        range = (cmd->data_length / dev->se_sub_dev->se_dev_attrib.block_size);
+        if (num_blocks != 0)
+                range = num_blocks;
+        else
+                range = (dev->transport->get_blocks(dev) - lba);
 
-        printk(KERN_INFO "WRITE_SAME UNMAP: LBA: %llu Range: %u\n",
-                         (unsigned long long)lba, range);
+        printk(KERN_INFO "WRITE_SAME UNMAP: LBA: %llu Range: %llu\n",
+                 (unsigned long long)lba, (unsigned long long)range);
 
         ret = dev->transport->do_discard(dev, lba, range);
         if (ret < 0) {
@@ -1081,7 +1093,7 @@ transport_emulate_control_cdb(struct se_task *task)
                                         " for: %s\n", dev->transport->name);
                         return PYX_TRANSPORT_UNKNOWN_SAM_OPCODE;
                 }
-                ret = target_emulate_write_same(task);
+                ret = target_emulate_write_same(task, 0);
                 break;
         case VARIABLE_LENGTH_CMD:
                 service_action =
@@ -1094,7 +1106,7 @@ transport_emulate_control_cdb(struct se_task *task)
                                         dev->transport->name);
                                 return PYX_TRANSPORT_UNKNOWN_SAM_OPCODE;
                         }
-                        ret = target_emulate_write_same(task);
+                        ret = target_emulate_write_same(task, 1);
                         break;
                 default:
                         printk(KERN_ERR "Unsupported VARIABLE_LENGTH_CMD SA:"
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index a29f6d3fc55..bf401da05f3 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -3132,7 +3132,12 @@ static int transport_generic_cmd_sequencer(
                         sectors = transport_get_sectors_32(cdb, cmd, &sector_ret);
                         if (sector_ret)
                                 goto out_unsupported_cdb;
-                        size = transport_get_size(sectors, cdb, cmd);
+
+                        if (sectors != 0)
+                                size = transport_get_size(sectors, cdb, cmd);
+                        else
+                                size = dev->se_sub_dev->se_dev_attrib.block_size;
+
                         cmd->t_task.t_task_lba = get_unaligned_be64(&cdb[12]);
                         cmd->se_cmd_flags |= SCF_SCSI_CONTROL_SG_IO_CDB;
 
@@ -3416,7 +3421,12 @@ static int transport_generic_cmd_sequencer(
                 sectors = transport_get_sectors_16(cdb, cmd, &sector_ret);
                 if (sector_ret)
                         goto out_unsupported_cdb;
-                size = transport_get_size(sectors, cdb, cmd);
+
+                if (sectors != 0)
+                        size = transport_get_size(sectors, cdb, cmd);
+                else
+                        size = dev->se_sub_dev->se_dev_attrib.block_size;
+
                 cmd->t_task.t_task_lba = get_unaligned_be64(&cdb[2]);
                 passthrough = (dev->transport->transport_type ==
                                 TRANSPORT_PLUGIN_PHBA_PDEV);