From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f170.google.com (mail-ig0-f170.google.com [209.85.213.170]) by kanga.kvack.org (Postfix) with ESMTP id EB2066B0035 for ; Thu, 10 Apr 2014 20:22:14 -0400 (EDT) Received: by mail-ig0-f170.google.com with SMTP id uq10so1444711igb.1 for ; Thu, 10 Apr 2014 17:22:14 -0700 (PDT) Received: from mail-ie0-x235.google.com (mail-ie0-x235.google.com [2607:f8b0:4001:c03::235]) by mx.google.com with ESMTPS id lp10si583100igb.41.2014.04.10.17.22.13 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 10 Apr 2014 17:22:14 -0700 (PDT) Received: by mail-ie0-f181.google.com with SMTP id tp5so4467900ieb.26 for ; Thu, 10 Apr 2014 17:22:13 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <53470E26.2030306@cybernetics.com> References: <53470E26.2030306@cybernetics.com> Date: Fri, 11 Apr 2014 02:22:13 +0200 Message-ID: Subject: Re: [PATCH 2/6] shm: add sealing API From: David Herrmann Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Tony Battersby Cc: linux-kernel , linux-fsdevel , linux-mm , "dri-devel@lists.freedesktop.org" Hi On Thu, Apr 10, 2014 at 11:33 PM, Tony Battersby wrote: > For O_DIRECT the kernel pins the submitted pages in memory for DMA by > incrementing the page reference counts when the I/O is submitted, > allowing the pages to be modified by DMA even if they are no longer > mapped in the address space of the process. This is different from a > regular read(), which uses the CPU to copy the data and will fail if the > pages are not mapped. Can you please provide an example code-path? For instance, file_read_actor() does not pin any pages but only keeps the user-space address and resolves it once it has data to write. Thanks David -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org