Received-SPF: pass (google.com: domain of linux-kernel+bounces-46774-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Wed, 31 Jan 2024 08:16:54 -0800
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Jiri Slaby <jirislaby@kernel.org>
Cc: Joe Damato <jdamato@fastly.com>, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, chuck.lever@oracle.com, jlayton@kernel.org,
	linux-api@vger.kernel.org, brauner@kernel.org, edumazet@google.com,
	davem@davemloft.net, alexander.duyck@gmail.com,
	sridhar.samudrala@intel.com, kuba@kernel.org,
	willemdebruijn.kernel@gmail.com, weiwan@google.com,
	David.Laight@aculab.com, arnd@arndb.de,
	Jonathan Corbet <corbet@lwn.net>,
	Alexander Viro <viro@zeniv.linux.org.uk>, Jan Kara <jack@suse.cz>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Nathan Lynch <nathanl@linux.ibm.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Maik Broemme <mbroemme@libmpq.org>,
	Steve French <stfrench@microsoft.com>,
	Julien Panis <jpanis@baylibre.com>, Thomas Huth <thuth@redhat.com>,
	Andrew Waterman <waterman@eecs.berkeley.edu>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	"open list:FILESYSTEMS (VFS and infrastructure)" <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH net-next v4 3/3] eventpoll: Add epoll ioctl for
 epoll_params
Message-ID: <2024013145-payment-enjoyment-6274@gregkh>
References: <20240131014738.469858-1-jdamato@fastly.com>
 <20240131014738.469858-4-jdamato@fastly.com>
 <2024013001-prison-strum-899d@gregkh>
 <20240131022756.GA4837@fastly.com>
 <efee9789-4f05-4202-9a95-21d88f6307b0@kernel.org>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <efee9789-4f05-4202-9a95-21d88f6307b0@kernel.org>

On Wed, Jan 31, 2024 at 07:03:54AM +0100, Jiri Slaby wrote:
> On 31. 01. 24, 3:27, Joe Damato wrote:
> > On Tue, Jan 30, 2024 at 06:08:36PM -0800, Greg Kroah-Hartman wrote:
> > > On Wed, Jan 31, 2024 at 01:47:33AM +0000, Joe Damato wrote:
> > > > +struct epoll_params {
> > > > +	__aligned_u64 busy_poll_usecs;
> > > > +	__u16 busy_poll_budget;
> > > > +
> > > > +	/* pad the struct to a multiple of 64bits for alignment on all arches */
> > > > +	__u8 __pad[6];
> > > 
> > > You HAVE to check this padding to be sure it is all 0, otherwise it can
> > > never be used in the future for anything.
> > 
> > Is there some preferred mechanism for this in the kernel that I should be
> > using or is this as simple as adding a for loop to check each u8 == 0 ?
> 
> You are likely looking for memchr_inv().

Ah, never noticed that, thanks!