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>

fs/nfs/nfs3proc.c

@@ -398,8 +398,7 @@ nfs3_proc_remove(struct inode *dir, struct qstr *name)
 {
 	struct nfs_removeargs arg = {
 		.fh = NFS_FH(dir),
-		.name.len = name->len,
-		.name.name = name->name,
+		.name = *name,
 	};
 	struct nfs_removeres res;
 	struct rpc_message msg = {