From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f46.google.com (mail-pb0-f46.google.com [209.85.160.46]) by kanga.kvack.org (Postfix) with ESMTP id 4B2426B0032 for ; Tue, 8 Oct 2013 12:24:09 -0400 (EDT) Received: by mail-pb0-f46.google.com with SMTP id rq2so8832444pbb.19 for ; Tue, 08 Oct 2013 09:24:08 -0700 (PDT) Message-ID: <52543185.3060705@sr71.net> Date: Tue, 08 Oct 2013 09:23:33 -0700 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [PATCH 1/2] vmsplice: unmap gifted pages for recipient References: <1381177293-27125-1-git-send-email-rcj@linux.vnet.ibm.com> <1381177293-27125-2-git-send-email-rcj@linux.vnet.ibm.com> In-Reply-To: <1381177293-27125-2-git-send-email-rcj@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Robert C Jennings , linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Alexander Viro , Rik van Riel , Andrea Arcangeli , Matt Helsley , Anthony Liguori , Michael Roth , Lei Li , Leonardo Garcia , Vlastimil Babka On 10/07/2013 01:21 PM, Robert C Jennings wrote: > spd.partial[page_nr].offset = loff; > spd.partial[page_nr].len = this_len; > + spd.partial[page_nr].useraddr = index << PAGE_CACHE_SHIFT; > len -= this_len; > loff = 0; > spd.nr_pages++; > @@ -656,6 +702,7 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos, > this_len = min_t(size_t, vec[i].iov_len, res); > spd.partial[i].offset = 0; > spd.partial[i].len = this_len; > + spd.partial[i].useraddr = (unsigned long)vec[i].iov_base; > if (!this_len) { > __free_page(spd.pages[i]); > spd.pages[i] = NULL; > @@ -1475,6 +1522,8 @@ static int get_iovec_page_array(const struct iovec __user *iov, > > partial[buffers].offset = off; > partial[buffers].len = plen; > + partial[buffers].useraddr = (unsigned long)base; > + base = (void*)((unsigned long)base + PAGE_SIZE); > > off = 0; > len -= plen; > diff --git a/include/linux/splice.h b/include/linux/splice.h > index 74575cb..56661e3 100644 > --- a/include/linux/splice.h > +++ b/include/linux/splice.h > @@ -44,6 +44,7 @@ struct partial_page { > unsigned int offset; > unsigned int len; > unsigned long private; > + unsigned long useraddr; > }; "useraddr" confuses me. You make it an 'unsigned long', yet two of the three assignments are from "void __user *". The other assignment: spd.partial[page_nr].useraddr = index << PAGE_CACHE_SHIFT; 'index' looks to be the offset inside the file, not a user address, so I'm confused what that is doing. Could you elaborate a little more on why 'useraddr' is suddenly needed in these patches? How is "index << PAGE_CACHE_SHIFT" a virtual address? Also, are we losing any of the advantages of sparse checking since 'useraddr' is without the __user annotation? -- 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