xen-blkfront: remove type check from blkfront_setup_discard

In its initial implementation a check for "type" was added, but only phy
and file are handled. This breaks advertised discard support for other
type values such as qdisk.

Fix and simplify this function: If the backend advertises discard
support it is supposed to implement it properly, so enable
feature_discard unconditionally. If the backend advertises the need for
a certain granularity and alignment then propagate both properties to
the blocklayer. The discard-secure property is a boolean, update the code
to reflect that.
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/block/xen-blkfront.c

@@ -1635,23 +1635,16 @@ blkfront_closing(struct blkfront_info *info)
 static void blkfront_setup_discard(struct blkfront_info *info)
 {
 	int err;
-	char *type;
 	unsigned int discard_granularity;
 	unsigned int discard_alignment;
 	unsigned int discard_secure;
 
-	type = xenbus_read(XBT_NIL, info->xbdev->otherend, "type", NULL);
-	if (IS_ERR(type))
-		return;
-
-	info->feature_secdiscard = 0;
-	if (strncmp(type, "phy", 3) == 0) {
+	info->feature_discard = 1;
 	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
 		"discard-granularity", "%u", &discard_granularity,
 		"discard-alignment", "%u", &discard_alignment,
 		NULL);
 	if (!err) {
-			info->feature_discard = 1;
 		info->discard_granularity = discard_granularity;
 		info->discard_alignment = discard_alignment;
 	}
@@ -1659,12 +1652,7 @@ static void blkfront_setup_discard(struct blkfront_info *info)
 		    "discard-secure", "%d", &discard_secure,
 		    NULL);
 	if (!err)
-			info->feature_secdiscard = discard_secure;
-
-	} else if (strncmp(type, "file", 4) == 0)
-		info->feature_discard = 1;
-
-	kfree(type);
+		info->feature_secdiscard = !!discard_secure;
 }
 
 static int blkfront_setup_indirect(struct blkfront_info *info)