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[49.181.38.249]) by smtp.gmail.com with ESMTPSA id d13-20020a63d70d000000b005cd821a01d4sm9196297pgg.28.2024.01.30.18.57.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jan 2024 18:57:08 -0800 (PST) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1rV0mf-00Ha2x-0d; Wed, 31 Jan 2024 13:57:05 +1100 Date: Wed, 31 Jan 2024 13:57:05 +1100 From: Dave Chinner To: Joe Damato Cc: Greg Kroah-Hartman , 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 , Alexander Viro , Jan Kara , Michael Ellerman , Nathan Lynch , Thomas Zimmermann , Maik Broemme , Steve French , Julien Panis , Jiri Slaby , Thomas Huth , Andrew Waterman , Albert Ou , Palmer Dabbelt , "open list:DOCUMENTATION" , "open list:FILESYSTEMS (VFS and infrastructure)" Subject: Re: [PATCH net-next v4 3/3] eventpoll: Add epoll ioctl for epoll_params Message-ID: References: <20240131014738.469858-1-jdamato@fastly.com> <20240131014738.469858-4-jdamato@fastly.com> <2024013001-prison-strum-899d@gregkh> <20240131022756.GA4837@fastly.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240131022756.GA4837@fastly.com> On Tue, Jan 30, 2024 at 06:27:57PM -0800, 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 ? memchr_inv() -Dave. -- Dave Chinner david@fromorbit.com