target/sbc: Add LBPRZ attribute + control CDB emulation

This change sets the LBPRZ flag in EVPD page b2h and READ CAPACITY (16)
based on a new unmap_zeroes_data device attribute. This flag is set
automatically for iblock based on underlying block device queue's
discard_zeroes_data flag.
Signed-off-by: Jamie Pocas <jamie.pocas@emc.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_configfs.c

@@ -499,6 +499,7 @@ DEF_CONFIGFS_ATTRIB_SHOW(max_unmap_lba_count);
 DEF_CONFIGFS_ATTRIB_SHOW(max_unmap_block_desc_count);
 DEF_CONFIGFS_ATTRIB_SHOW(unmap_granularity);
 DEF_CONFIGFS_ATTRIB_SHOW(unmap_granularity_alignment);
+DEF_CONFIGFS_ATTRIB_SHOW(unmap_zeroes_data);
 DEF_CONFIGFS_ATTRIB_SHOW(max_write_same_len);
 
 #define DEF_CONFIGFS_ATTRIB_STORE_U32(_name)				\
@@ -866,6 +867,39 @@ static ssize_t emulate_rest_reord_store(struct config_item *item,
 	return count;
 }
 
+static ssize_t unmap_zeroes_data_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct se_dev_attrib *da = to_attrib(item);
+	bool flag;
+	int ret;
+
+	ret = strtobool(page, &flag);
+	if (ret < 0)
+		return ret;
+
+	if (da->da_dev->export_count) {
+		pr_err("dev[%p]: Unable to change SE Device"
+		       " unmap_zeroes_data while export_count is %d\n",
+		       da->da_dev, da->da_dev->export_count);
+		return -EINVAL;
+	}
+	/*
+	 * We expect this value to be non-zero when generic Block Layer
+	 * Discard supported is detected iblock_configure_device().
+	 */
+	if (flag && !da->max_unmap_block_desc_count) {
+		pr_err("dev[%p]: Thin Provisioning LBPRZ will not be set"
+		       " because max_unmap_block_desc_count is zero\n",
+		       da->da_dev);
+	       return -ENOSYS;
+	}
+	da->unmap_zeroes_data = flag;
+	pr_debug("dev[%p]: SE Device Thin Provisioning LBPRZ bit: %d\n",
+		 da->da_dev, flag);
+	return 0;
+}
+
 /*
  * Note, this can only be called on unexported SE Device Object.
  */
@@ -998,6 +1032,7 @@ CONFIGFS_ATTR(, max_unmap_lba_count);
 CONFIGFS_ATTR(, max_unmap_block_desc_count);
 CONFIGFS_ATTR(, unmap_granularity);
 CONFIGFS_ATTR(, unmap_granularity_alignment);
+CONFIGFS_ATTR(, unmap_zeroes_data);
 CONFIGFS_ATTR(, max_write_same_len);
 
 /*
@@ -1034,6 +1069,7 @@ struct configfs_attribute *sbc_attrib_attrs[] = {
 	&attr_max_unmap_block_desc_count,
 	&attr_unmap_granularity,
 	&attr_unmap_granularity_alignment,
+	&attr_unmap_zeroes_data,
 	&attr_max_write_same_len,
 	NULL,
 };

drivers/target/target_core_device.c

@@ -813,6 +813,8 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
 	dev->dev_attrib.unmap_granularity = DA_UNMAP_GRANULARITY_DEFAULT;
 	dev->dev_attrib.unmap_granularity_alignment =
 				DA_UNMAP_GRANULARITY_ALIGNMENT_DEFAULT;
+	dev->dev_attrib.unmap_zeroes_data =
+				DA_UNMAP_ZEROES_DATA_DEFAULT;
 	dev->dev_attrib.max_write_same_len = DA_MAX_WRITE_SAME_LEN;
 
 	xcopy_lun = &dev->xcopy_lun;

drivers/target/target_core_iblock.c

@@ -138,6 +138,8 @@ static int iblock_configure_device(struct se_device *dev)
 				q->limits.discard_granularity >> 9;
 		dev->dev_attrib.unmap_granularity_alignment =
 				q->limits.discard_alignment;
+		dev->dev_attrib.unmap_zeroes_data =
+				q->limits.discard_zeroes_data;
 
 		pr_debug("IBLOCK: BLOCK Discard support available,"
 				" disabled by default\n");

drivers/target/target_core_sbc.c

@@ -141,9 +141,17 @@ sbc_emulate_readcapacity_16(struct se_cmd *cmd)
 	 * Set Thin Provisioning Enable bit following sbc3r22 in section
 	 * READ CAPACITY (16) byte 14 if emulate_tpu or emulate_tpws is enabled.
 	 */
-	if (dev->dev_attrib.emulate_tpu || dev->dev_attrib.emulate_tpws)
+	if (dev->dev_attrib.emulate_tpu || dev->dev_attrib.emulate_tpws) {
 		buf[14] |= 0x80;
 
+		/*
+		 * LBPRZ signifies that zeroes will be read back from an LBA after
+		 * an UNMAP or WRITE SAME w/ unmap bit (sbc3r36 5.16.2)
+		 */
+		if (dev->dev_attrib.unmap_zeroes_data)
+			buf[14] |= 0x40;
+	}
+
 	rbuf = transport_kmap_data_sg(cmd);
 	if (rbuf) {
 		memcpy(rbuf, buf, min_t(u32, sizeof(buf), cmd->data_length));

drivers/target/target_core_spc.c

@@ -635,6 +635,18 @@ spc_emulate_evpd_b2(struct se_cmd *cmd, unsigned char *buf)
 	if (dev->dev_attrib.emulate_tpws != 0)
 		buf[5] |= 0x40 | 0x20;
 
+	/*
+	 * The unmap_zeroes_data set means that the underlying device supports
+	 * REQ_DISCARD and has the discard_zeroes_data bit set. This satisfies
+	 * the SBC requirements for LBPRZ, meaning that a subsequent read
+	 * will return zeroes after an UNMAP or WRITE SAME (16) to an LBA
+	 * See sbc4r36 6.6.4.
+	 */
+	if (((dev->dev_attrib.emulate_tpu != 0) ||
+	     (dev->dev_attrib.emulate_tpws != 0)) &&
+	     (dev->dev_attrib.unmap_zeroes_data != 0))
+		buf[5] |= 0x04;
+
 	return 0;
 }
 

include/target/target_core_base.h

@@ -63,6 +63,8 @@
 #define DA_UNMAP_GRANULARITY_DEFAULT		0
 /* Default unmap_granularity_alignment */
 #define DA_UNMAP_GRANULARITY_ALIGNMENT_DEFAULT	0
+/* Default unmap_zeroes_data */
+#define DA_UNMAP_ZEROES_DATA_DEFAULT		0
 /* Default max_write_same_len, disabled by default */
 #define DA_MAX_WRITE_SAME_LEN			0
 /* Use a model alias based on the configfs backend device name */
@@ -674,6 +676,7 @@ struct se_dev_attrib {
 	int		force_pr_aptpl;
 	int		is_nonrot;
 	int		emulate_rest_reord;
+	int		unmap_zeroes_data;
 	u32		hw_block_size;
 	u32		block_size;
 	u32		hw_max_sectors;