From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755941Ab0JHI3Z (ORCPT ); Fri, 8 Oct 2010 04:29:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35072 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752722Ab0JHI3X (ORCPT ); Fri, 8 Oct 2010 04:29:23 -0400 Message-ID: <4CAED656.2080300@redhat.com> Date: Fri, 08 Oct 2010 10:29:10 +0200 From: Jerome Marchand User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.4pre) Gecko/20091014 Fedora/3.0-2.8.b4.fc11 Thunderbird/3.0b4 MIME-Version: 1.0 To: Andrew Morton CC: Matthew Wilcox , Pavel Emelyanov , Linux Kernel Mailing List , xiyou.wangcong@gmail.com Subject: Re: [PATCH v2] procfs: fix numbering in /proc/locks References: <4CA484BA.7090809@redhat.com> <4CAB1693.2080301@redhat.com> <20101007162702.7db08f5b.akpm@linux-foundation.org> In-Reply-To: <20101007162702.7db08f5b.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/08/2010 01:27 AM, Andrew Morton wrote: > On Tue, 05 Oct 2010 14:14:11 +0200 > Jerome Marchand wrote: > >> On 09/30/2010 02:38 PM, Jerome Marchand wrote: >>> >>> The lock number in /proc/locks (first field) is implemented by a counter >>> (private field of struct seq_file) which is incremented at each call of >>> locks_show() and reset to 1 in locks_start() whatever the offset is. It >>> should be reset according to the actual position in the list. >>> >>> Moreover, locks_show() can be called twice to print a single line thus >>> skipping a number. The counter should be incremented in locks_next(). >>> >>> Signed-off-by: Jerome Marchand >>> --- >>> locks.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/fs/locks.c b/fs/locks.c >>> index ab24d49..49d7343 100644 >>> --- a/fs/locks.c >>> +++ b/fs/locks.c >>> @@ -2166,19 +2166,19 @@ static int locks_show(struct seq_file *f, void *v) >>> list_for_each_entry(bfl, &fl->fl_block, fl_block) >>> lock_get_status(f, bfl, (long)f->private, " ->"); >>> >>> - f->private++; >>> return 0; >>> } >>> >>> static void *locks_start(struct seq_file *f, loff_t *pos) >>> { >>> lock_kernel(); >>> - f->private = (void *)1; >>> + f->private = (void *) (*pos + 1); >> >> That cast trigger a warning on some arch: >> "warning: cast to pointer from integer of different size" >> >> There is no real risk here. At worst /proc/locks will show wrong number >> if there is more than 2^32 locks, but should I mute the warning it with >> something like: >> f->private = (void *) (size_t) (*pos + 1); >> ? > > Putting a loff_t into a void* is a pretty alarming thing to do. If > we're really going to do that then use a (long) cast and put a very > good comment at the code site explaining why the bug doesn't matter, so > people aren't misled. > > But really, why sweat it? kmalloc the eight bytes, make ->private > point at that and we never have to think about it again. Bonus points > for doing this without any typecasts ;) > That's definitely cleaner. I'll do that. Thanks, Jerome