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>

3 files changed, 47 insertions, 1 deletions

diff --git a/drivers/target/target_core_cdb.c b/drivers/target/target_core_cdb.c
index 982830023661..145739bcf752 100644
--- a/drivers/target/target_core_cdb.c
+++ b/drivers/target/target_core_cdb.c
@@ -775,6 +775,35 @@ target_modesense_control(struct se_device *dev, unsigned char *p)
         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
          *
          * Unit Attention interlocks control (UN_INTLCK_CTRL) to code 00b
diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index e56c39daeec6..a92176d2e187 100644
--- a/drivers/target/target_core_configfs.c
+++ b/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,
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 81860ddc7cc4..b38b6c993e65 100644
--- a/drivers/target/target_core_device.c
+++ b/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.
  */