From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752695AbbFHISI (ORCPT ); Mon, 8 Jun 2015 04:18:08 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38353 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752439AbbFHIR5 (ORCPT ); Mon, 8 Jun 2015 04:17:57 -0400 Date: Mon, 8 Jun 2015 10:17:51 +0200 From: Michal Hocko To: Piotr Kwapulinski Cc: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, riel@redhat.com, sasha.levin@oracle.com, dave@stgolabs.net, koct9i@gmail.com, pfeiner@google.com, dh.herrmann@gmail.com, vishnu.ps@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/mmap.c: optimization of do_mmap_pgoff function Message-ID: <20150608081751.GC1380@dhcp22.suse.cz> References: <1433584472-19151-1-git-send-email-kwapulinski.piotr@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1433584472-19151-1-git-send-email-kwapulinski.piotr@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 06-06-15 11:54:32, Piotr Kwapulinski wrote: > The simple check for zero length memory mapping may be performed > earlier. It causes that in case of zero length memory mapping some > unnecessary code is not executed at all. It does not make the code less > readable and saves some CPU cycles. > > Signed-off-by: Piotr Kwapulinski Acked-by: Michal Hocko > --- > mm/mmap.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index bb50cac..aa632ad 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1258,6 +1258,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, > > *populate = 0; > > + if (!len) > + return -EINVAL; > + > /* > * Does the application expect PROT_READ to imply PROT_EXEC? > * > @@ -1268,9 +1271,6 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, > if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC))) > prot |= PROT_EXEC; > > - if (!len) > - return -EINVAL; > - > if (!(flags & MAP_FIXED)) > addr = round_hint_to_min(addr); > > -- > 2.3.7 > -- Michal Hocko SUSE Labs