target: Update QUEUE ALGORITHM MODIFIER control page default

This patch adds the default 'Unrestricted reordering allowed' for SCSI
control mode page QUEUE ALGORITHM MODIFIER on a per se_device basis in
target_modesense_control() following spc4r23.  This includes a new
emuluate_rest_reord configfs attribute that currently (only) accepts
zero to signal 'Unrestricted reordering allowed' in control mode page
usage by the backend target device.

Reported-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@risingtidesystems.com>

drivers/target/target_core_cdb.c

@@ -774,6 +774,35 @@ target_modesense_control(struct se_device *dev, unsigned char *p)
 	p[0] = 0x0a;
 	p[1] = 0x0a;
 	p[2] = 2;
+	/*
+	 * From spc4r23, 7.4.7 Control mode page
+	 *
+	 * The QUEUE ALGORITHM MODIFIER field (see table 368) specifies
+	 * restrictions on the algorithm used for reordering commands
+	 * having the SIMPLE task attribute (see SAM-4).
+	 *
+	 *                    Table 368 -- QUEUE ALGORITHM MODIFIER field
+	 *                         Code      Description
+	 *                          0h       Restricted reordering
+	 *                          1h       Unrestricted reordering allowed
+	 *                          2h to 7h    Reserved
+	 *                          8h to Fh    Vendor specific
+	 *
+	 * A value of zero in the QUEUE ALGORITHM MODIFIER field specifies that
+	 * the device server shall order the processing sequence of commands
+	 * having the SIMPLE task attribute such that data integrity is maintained
+	 * for that I_T nexus (i.e., if the transmission of new SCSI transport protocol
+	 * requests is halted at any time, the final value of all data observable
+	 * on the medium shall be the same as if all the commands had been processed
+	 * with the ORDERED task attribute).
+	 *
+	 * A value of one in the QUEUE ALGORITHM MODIFIER field specifies that the
+	 * device server may reorder the processing sequence of commands having the
+	 * SIMPLE task attribute in any manner. Any data integrity exposures related to
+	 * command sequence order shall be explicitly handled by the application client
+	 * through the selection of appropriate ommands and task attributes.
+	 */
+	p[3] = (dev->se_sub_dev->se_dev_attrib.emulate_rest_reord == 1) ? 0x00 : 0x10;
 	/*
 	 * From spc4r17, section 7.4.6 Control mode Page
 	 *

drivers/target/target_core_configfs.c

@@ -701,6 +701,9 @@ SE_DEV_ATTR(enforce_pr_isids, S_IRUGO | S_IWUSR);
 DEF_DEV_ATTRIB(is_nonrot);
 SE_DEV_ATTR(is_nonrot, S_IRUGO | S_IWUSR);
 
+DEF_DEV_ATTRIB(emulate_rest_reord);
+SE_DEV_ATTR(emulate_rest_reord, S_IRUGO | S_IWUSR);
+
 DEF_DEV_ATTRIB_RO(hw_block_size);
 SE_DEV_ATTR_RO(hw_block_size);
 
@@ -750,6 +753,7 @@ static struct configfs_attribute *target_core_dev_attrib_attrs[] = {
 	&target_core_dev_attrib_emulate_tpws.attr,
 	&target_core_dev_attrib_enforce_pr_isids.attr,
 	&target_core_dev_attrib_is_nonrot.attr,
+	&target_core_dev_attrib_emulate_rest_reord.attr,
 	&target_core_dev_attrib_hw_block_size.attr,
 	&target_core_dev_attrib_block_size.attr,
 	&target_core_dev_attrib_hw_max_sectors.attr,

drivers/target/target_core_device.c

@@ -857,6 +857,7 @@ void se_dev_set_default_attribs(
 	dev->se_sub_dev->se_dev_attrib.emulate_alua = DA_EMULATE_ALUA;
 	dev->se_sub_dev->se_dev_attrib.enforce_pr_isids = DA_ENFORCE_PR_ISIDS;
 	dev->se_sub_dev->se_dev_attrib.is_nonrot = DA_IS_NONROT;
+	dev->se_sub_dev->se_dev_attrib.emulate_rest_reord = DA_EMULATE_REST_REORD;
 	/*
 	 * The TPU=1 and TPWS=1 settings will be set in TCM/IBLOCK
 	 * iblock_create_virtdevice() from struct queue_limits values
@@ -1128,11 +1129,23 @@ int se_dev_set_is_nonrot(struct se_device *dev, int flag)
 		return -EINVAL;
 	}
 	dev->se_sub_dev->se_dev_attrib.is_nonrot = flag;
-	printk(KERN_INFO "dev[%p]: SE Device is_nonrot bit: %d\n",
+	pr_debug("dev[%p]: SE Device is_nonrot bit: %d\n",
 	       dev, flag);
 	return 0;
 }
 
+int se_dev_set_emulate_rest_reord(struct se_device *dev, int flag)
+{
+	if (flag != 0) {
+		printk(KERN_ERR "dev[%p]: SE Device emulatation of restricted"
+			" reordering not implemented\n", dev);
+		return -ENOSYS;
+	}
+	dev->se_sub_dev->se_dev_attrib.emulate_rest_reord = flag;
+	pr_debug("dev[%p]: SE Device emulate_rest_reord: %d\n", dev, flag);
+	return 0;
+}
+
 /*
  * Note, this can only be called on unexported SE Device Object.
  */

include/target/target_core_base.h

@@ -662,6 +662,7 @@ struct se_dev_attrib {
 	int		emulate_alua;
 	int		enforce_pr_isids;
 	int		is_nonrot;
+	int		emulate_rest_reord;
 	u32		hw_block_size;
 	u32		block_size;
 	u32		hw_max_sectors;

include/target/target_core_device.h

@@ -40,6 +40,7 @@ extern int se_dev_set_emulate_tpu(struct se_device *, int);
 extern int se_dev_set_emulate_tpws(struct se_device *, int);
 extern int se_dev_set_enforce_pr_isids(struct se_device *, int);
 extern int se_dev_set_is_nonrot(struct se_device *, int);
+extern int se_dev_set_emulate_rest_reord(struct se_device *dev, int);
 extern int se_dev_set_queue_depth(struct se_device *, u32);
 extern int se_dev_set_max_sectors(struct se_device *, u32);
 extern int se_dev_set_optimal_sectors(struct se_device *, u32);

include/target/target_core_transport.h

@@ -103,6 +103,8 @@
 #define DA_STATUS_MAX_SECTORS_MAX		8192
 /* By default don't report non-rotating (solid state) medium */
 #define DA_IS_NONROT				0
+/* Queue Algorithm Modifier default for restricted reordering in control mode page */
+#define DA_EMULATE_REST_REORD			0
 
 #define SE_MODE_PAGE_BUF			512