From mboxrd@z Thu Jan 1 00:00:00 1970 From: Haggai Eran Subject: Re: [PATCH for-next V1 2/5] IB/core: Add ib_is_udata_cleared Date: Thu, 10 Dec 2015 17:20:30 +0200 Message-ID: <5669983E.5000200@mellanox.com> References: <1449157463-25313-1-git-send-email-matanb@mellanox.com> <1449157463-25313-3-git-send-email-matanb@mellanox.com> <56658718.8080308@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Matan Barak Cc: Matan Barak , Eli Cohen , linux-rdma , Doug Ledford , Eran Ben Elisha , Yann Droneaud List-Id: linux-rdma@vger.kernel.org On 10/12/2015 16:59, Matan Barak wrote: > On Mon, Dec 7, 2015 at 3:18 PM, Haggai Eran wrote: >> On 12/03/2015 05:44 PM, Matan Barak wrote: >>> Extending core and vendor verb commands require us to check that the >>> unknown part of the user's given command is all zeros. >>> Adding ib_is_udata_cleared in order to do so. >>> >> >> Why not copy the data into kernel space and run memchr_inv() on it? >> > > Probably less efficient, isn't it? Why do you think it is less efficient? I'm not sure calling copy_from_user multiple times is very efficient. For once, you are calling access_ok multiple times. I guess it depends on the amount of data you are copying. > I know it isn't data path, but we'll execute this code in all extended > functions (sometimes even more than once). Do you think it is important enough to maintain our own copy of memchr_inv()? -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html