fs: dcache reduce branches in lookup path

Reduce some branches and memory accesses in dcache lookup by adding dentry
flags to indicate common d_ops are set, rather than having to check them.
This saves a pointer memory access (dentry->d_op) in common path lookup
situations, and saves another pointer load and branch in cases where we
have d_op but not the particular operation.

Patched with:

git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

fs/adfs/super.c

@@ -484,7 +484,7 @@ static int adfs_fill_super(struct super_block *sb, void *data, int silent)
 		adfs_error(sb, "get root inode failed\n");
 		goto error;
 	} else
-		sb->s_root->d_op = &adfs_dentry_operations;
+		d_set_d_op(sb->s_root, &adfs_dentry_operations);
 	unlock_kernel();
 	return 0;