target: export lio pgr/alua support as device attr

Older kernels could crash or hang if the user write/read some ALUA files
with pscsi and tcmu backends. This patch exports if LIO supports
executing PGR and ALUA scsi commands/checks for the se_device, so userspace
can easily test.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_configfs.c

@@ -1085,6 +1085,24 @@ static ssize_t block_size_store(struct config_item *item,
 	return count;
 }
 
+static ssize_t alua_support_show(struct config_item *item, char *page)
+{
+	struct se_dev_attrib *da = to_attrib(item);
+	u8 flags = da->da_dev->transport->transport_flags;
+
+	return snprintf(page, PAGE_SIZE, "%d\n",
+			flags & TRANSPORT_FLAG_PASSTHROUGH_ALUA ? 0 : 1);
+}
+
+static ssize_t pgr_support_show(struct config_item *item, char *page)
+{
+	struct se_dev_attrib *da = to_attrib(item);
+	u8 flags = da->da_dev->transport->transport_flags;
+
+	return snprintf(page, PAGE_SIZE, "%d\n",
+			flags & TRANSPORT_FLAG_PASSTHROUGH_PGR ? 0 : 1);
+}
+
 CONFIGFS_ATTR(, emulate_model_alias);
 CONFIGFS_ATTR(, emulate_dpo);
 CONFIGFS_ATTR(, emulate_fua_write);
@@ -1116,6 +1134,8 @@ CONFIGFS_ATTR(, unmap_granularity);
 CONFIGFS_ATTR(, unmap_granularity_alignment);
 CONFIGFS_ATTR(, unmap_zeroes_data);
 CONFIGFS_ATTR(, max_write_same_len);
+CONFIGFS_ATTR_RO(, alua_support);
+CONFIGFS_ATTR_RO(, pgr_support);
 
 /*
  * dev_attrib attributes for devices using the target core SBC/SPC
@@ -1154,6 +1174,8 @@ struct configfs_attribute *sbc_attrib_attrs[] = {
 	&attr_unmap_granularity_alignment,
 	&attr_unmap_zeroes_data,
 	&attr_max_write_same_len,
+	&attr_alua_support,
+	&attr_pgr_support,
 	NULL,
 };
 EXPORT_SYMBOL(sbc_attrib_attrs);
@@ -1168,6 +1190,8 @@ struct configfs_attribute *passthrough_attrib_attrs[] = {
 	&attr_hw_block_size,
 	&attr_hw_max_sectors,
 	&attr_hw_queue_depth,
+	&attr_alua_support,
+	&attr_pgr_support,
 	NULL,
 };
 EXPORT_SYMBOL(passthrough_attrib_attrs);