vfs: make it possible to access the dentry hash/len as one 64-bit entry

This allows comparing hash and len in one operation on 64-bit
architectures.  Right now only __d_lookup_rcu() takes advantage of this,
since that is the case we care most about.

The use of anonymous struct/unions hides the alternate 64-bit approach
from most users, the exception being a few cases where we initialize a
'struct qstr' with a static initializer.  This makes the problematic
cases use a new QSTR_INIT() helper function for that (but initializing
just the name pointer with a "{ .name = xyzzy }" initializer remains
valid, as does just copying another qstr structure).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index adf2990..7fee13b 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -127,9 +127,7 @@
 {
 	static uint32_t clntid;
 	char name[15];
-	struct qstr q = {
-		.name = name,
-	};
+	struct qstr q = { .name = name };
 	struct dentry *dir, *dentry;
 	int error;