block: Export integrity data interval size in sysfs

The size of the data interval was not exported in the sysfs integrity
directory. Export it so that userland apps can tell whether the interval
is different from the device's logical block size.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

Documentation/ABI/testing/sysfs-block

@@ -60,6 +60,13 @@ Description:
 		Indicates whether a storage device is capable of storing
 		integrity metadata. Set if the device is T10 PI-capable.
 
+What:		/sys/block/<disk>/integrity/protection_interval_bytes
+Date:		July 2015
+Contact:	Martin K. Petersen <martin.petersen@oracle.com>
+Description:
+		Describes the number of data bytes which are protected
+		by one integrity tuple. Typically the device's logical
+		block size.
 
 What:		/sys/block/<disk>/integrity/write_generate
 Date:		June 2008

block/blk-integrity.c

@@ -289,6 +289,14 @@ static ssize_t integrity_tag_size_show(struct blk_integrity *bi, char *page)
 		return sprintf(page, "0\n");
 }
 
+static ssize_t integrity_interval_show(struct blk_integrity *bi, char *page)
+{
+	if (bi != NULL)
+		return sprintf(page, "%u\n", 1 << bi->interval_exp);
+	else
+		return sprintf(page, "0\n");
+}
+
 static ssize_t integrity_verify_store(struct blk_integrity *bi,
 				      const char *page, size_t count)
 {
@@ -343,6 +351,11 @@ static struct integrity_sysfs_entry integrity_tag_size_entry = {
 	.show = integrity_tag_size_show,
 };
 
+static struct integrity_sysfs_entry integrity_interval_entry = {
+	.attr = { .name = "protection_interval_bytes", .mode = S_IRUGO },
+	.show = integrity_interval_show,
+};
+
 static struct integrity_sysfs_entry integrity_verify_entry = {
 	.attr = { .name = "read_verify", .mode = S_IRUGO | S_IWUSR },
 	.show = integrity_verify_show,
@@ -363,6 +376,7 @@ static struct integrity_sysfs_entry integrity_device_entry = {
 static struct attribute *integrity_attrs[] = {
 	&integrity_format_entry.attr,
 	&integrity_tag_size_entry.attr,
+	&integrity_interval_entry.attr,
 	&integrity_verify_entry.attr,
 	&integrity_generate_entry.attr,
 	&integrity_device_entry.attr,