xen-blkback: prefer xenbus_scanf() over xenbus_gather()

... for single items being collected: It is more typesafe (as the
compiler can check format string and to-be-written-to variable match)
and requires one less parameter to be passed.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 3355f1c..bf09ffe 100644 (file)
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -1022,9 +1022,9 @@ static int connect_ring(struct backend_info *be)
        pr_debug("%s %s\n", __func__, dev->otherend);
 
        be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
-       err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
-                           "%63s", protocol, NULL);
-       if (err)
+       err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
+                          "%63s", protocol);
+       if (err <= 0)
                strcpy(protocol, "unspecified, assuming default");
        else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
                be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
@@ -1036,10 +1036,9 @@ static int connect_ring(struct backend_info *be)
                xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
                return -ENOSYS;
        }
-       err = xenbus_gather(XBT_NIL, dev->otherend,
-                           "feature-persistent", "%u",
-                           &pers_grants, NULL);
-       if (err)
+       err = xenbus_scanf(XBT_NIL, dev->otherend,
+                          "feature-persistent", "%u", &pers_grants);
+       if (err <= 0)
                pers_grants = 0;
 
        be->blkif->vbd.feature_gnt_persistent = pers_grants;