Linux: Clang build fixes

config/kernel-kmap-atomic-args.m4

@@ -7,7 +7,7 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_KMAP_ATOMIC_ARGS], [
 	ZFS_LINUX_TEST_SRC([kmap_atomic], [
 		#include <linux/pagemap.h>
 	],[
-		struct page page;
+		struct page page = {};
 		kmap_atomic(&page);
 	])
 ])

module/Kbuild.in

@@ -2,7 +2,7 @@
 # first.  This ensures its module initialization function is run before
 # any of the other module initialization functions which depend on it.
 
-ZFS_MODULE_CFLAGS += -std=gnu99 -Wno-declaration-after-statement
+ZFS_MODULE_CFLAGS += -std=gnu11 -Wno-declaration-after-statement
 ZFS_MODULE_CFLAGS += -Wmissing-prototypes
 ZFS_MODULE_CFLAGS += @KERNEL_DEBUG_CFLAGS@ @KERNEL_NO_FORMAT_ZERO_LENGTH@
 

udev/zvol_id.c

@@ -67,7 +67,7 @@ main(int argc, const char *const *argv)
 		return (1);
 	}
 
-	char zvol_name[MAXNAMELEN + strlen("-part") + 10];
+	char zvol_name[MAXNAMELEN+15];
 	if (ioctl(fd, BLKZNAME, zvol_name) == -1) {
 		fprintf(stderr, "%s: BLKZNAME: %s\n",
 		    dev_name, strerror(errno));