target: Report correct response length for some commands

When an initiator sends an allocation length bigger than what its
command consumes, the target should only return the actual response data
and set the residual length to the unused part of the allocation length.

Add a helper function that command handlers (INQUIRY, READ CAPACITY,
etc) can use to do this correctly, and use this code to get the correct
residual for commands that don't use the full initiator allocation in the
handlers for READ CAPACITY, READ CAPACITY(16), INQUIRY, MODE SENSE and
REPORT LUNS.

This addresses a handful of failures as reported by Christophe with
the Windows Certification Kit:

  http://permalink.gmane.org/gmane.linux.scsi.target.devel/6515

Signed-off-by: Roland Dreier <roland@purestorage.com>
Tested-by: Christophe Vu-Brugier <cvubrugier@yahoo.fr>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

4 files changed, 26 insertions, 5 deletions

diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index 97a33603795d..1d3a626bf24f 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -81,7 +81,7 @@ sbc_emulate_readcapacity(struct se_cmd *cmd)
 		transport_kunmap_data_sg(cmd);
 	}
 
-	target_complete_cmd(cmd, GOOD);
+	target_complete_cmd_with_length(cmd, GOOD, 8);
 	return 0;
 }
 
@@ -137,7 +137,7 @@ sbc_emulate_readcapacity_16(struct se_cmd *cmd)
 		transport_kunmap_data_sg(cmd);
 	}
 
-	target_complete_cmd(cmd, GOOD);
+	target_complete_cmd_with_length(cmd, GOOD, 32);
 	return 0;
 }
 
diff --git a/drivers/target/target_core_spc.c b/drivers/target/target_core_spc.c
index 17b5b7e099fa..6cd7222738fc 100644
--- a/drivers/target/target_core_spc.c
+++ b/drivers/target/target_core_spc.c
@@ -716,6 +716,7 @@ spc_emulate_inquiry(struct se_cmd *cmd)
 	unsigned char *buf;
 	sense_reason_t ret;
 	int p;
+	int len = 0;
 
 	buf = kzalloc(SE_INQUIRY_BUF, GFP_KERNEL);
 	if (!buf) {
@@ -737,6 +738,7 @@ spc_emulate_inquiry(struct se_cmd *cmd)
 		}
 
 		ret = spc_emulate_inquiry_std(cmd, buf);
+		len = buf[4] + 5;
 		goto out;
 	}
 
@@ -744,6 +746,7 @@ spc_emulate_inquiry(struct se_cmd *cmd)
 		if (cdb[2] == evpd_handlers[p].page) {
 			buf[1] = cdb[2];
 			ret = evpd_handlers[p].emulate(cmd, buf);
+			len = get_unaligned_be16(&buf[2]) + 4;
 			goto out;
 		}
 	}
@@ -760,7 +763,7 @@ out:
 	kfree(buf);
 
 	if (!ret)
-		target_complete_cmd(cmd, GOOD);
+		target_complete_cmd_with_length(cmd, GOOD, len);
 	return ret;
 }
 
@@ -1098,7 +1101,7 @@ set_length:
 		transport_kunmap_data_sg(cmd);
 	}
 
-	target_complete_cmd(cmd, GOOD);
+	target_complete_cmd_with_length(cmd, GOOD, length);
 	return 0;
 }
 
@@ -1274,7 +1277,7 @@ done:
 	buf[3] = (lun_count & 0xff);
 	transport_kunmap_data_sg(cmd);
 
-	target_complete_cmd(cmd, GOOD);
+	target_complete_cmd_with_length(cmd, GOOD, 8 + lun_count * 8);
 	return 0;
 }
 EXPORT_SYMBOL(spc_emulate_report_luns);
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 15dbf6e97289..c9e8b35a954f 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -703,6 +703,23 @@ void target_complete_cmd(struct se_cmd *cmd, u8 scsi_status)
 }
 EXPORT_SYMBOL(target_complete_cmd);
 
+void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int length)
+{
+	if (scsi_status == SAM_STAT_GOOD && length < cmd->data_length) {
+		if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) {
+			cmd->residual_count += cmd->data_length - length;
+		} else {
+			cmd->se_cmd_flags |= SCF_UNDERFLOW_BIT;
+			cmd->residual_count = cmd->data_length - length;
+		}
+
+		cmd->data_length = length;
+	}
+
+	target_complete_cmd(cmd, scsi_status);
+}
+EXPORT_SYMBOL(target_complete_cmd_with_length);
+
 static void target_add_to_state_list(struct se_cmd *cmd)
 {
 	struct se_device *dev = cmd->se_dev;
diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h
index 3a1c1eea1fff..9adc1bca1178 100644
--- a/include/target/target_core_backend.h
+++ b/include/target/target_core_backend.h
@@ -59,6 +59,7 @@ int	transport_subsystem_register(struct se_subsystem_api *);
 void	transport_subsystem_release(struct se_subsystem_api *);
 
 void	target_complete_cmd(struct se_cmd *, u8);
+void	target_complete_cmd_with_length(struct se_cmd *, u8, int);
 
 sense_reason_t	spc_parse_cdb(struct se_cmd *cmd, unsigned int *size);
 sense_reason_t	spc_emulate_report_luns(struct se_cmd *cmd);