From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f44.google.com (mail-wm0-f44.google.com [74.125.82.44]) by kanga.kvack.org (Postfix) with ESMTP id 4E5766B0038 for ; Mon, 23 Nov 2015 03:19:50 -0500 (EST) Received: by wmww144 with SMTP id w144so85431220wmw.1 for ; Mon, 23 Nov 2015 00:19:49 -0800 (PST) Received: from mail-wm0-f44.google.com (mail-wm0-f44.google.com. [74.125.82.44]) by mx.google.com with ESMTPS id c64si17646674wmi.55.2015.11.23.00.19.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 23 Nov 2015 00:19:49 -0800 (PST) Received: by wmec201 with SMTP id c201so148306179wme.0 for ; Mon, 23 Nov 2015 00:19:48 -0800 (PST) Date: Mon, 23 Nov 2015 09:19:47 +0100 From: Michal Hocko Subject: Re: [PATCH v2 2/2] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region Message-ID: <20151123081946.GA21050@dhcp22.suse.cz> References: <20151118162939.GA1842@home.local> <1448037734-4734-1-git-send-email-kwapulinski.piotr@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1448037734-4734-1-git-send-email-kwapulinski.piotr@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Piotr Kwapulinski Cc: akpm@linux-foundation.org, oleg@redhat.com, cmetcalf@ezchip.com, mszeredi@suse.cz, viro@zeniv.linux.org.uk, dave@stgolabs.net, kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com, aarcange@redhat.com, iamjoonsoo.kim@lge.com, jack@suse.cz, xiexiuqi@huawei.com, vbabka@suse.cz, Vineet.Gupta1@synopsys.com, riel@redhat.com, gang.chen.5i5j@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Fri 20-11-15 17:42:14, Piotr Kwapulinski wrote: > The following flag comparison in mmap_region makes no sense: > > if (!(vm_flags & MAP_FIXED)) > return -ENOMEM; > > The condition is always false and thus the above "return -ENOMEM" is never > executed. The vm_flags must not be compared with MAP_FIXED flag. > The vm_flags may only be compared with VM_* flags. > MAP_FIXED has the same value as VM_MAYREAD. > It has no user visible effect. > > Remove the code that makes no sense. > > Signed-off-by: Piotr Kwapulinski I think this is preferable. Hitting the rlimit is a slow path and find_vma_intersection should realize that there is no overlapping VMA for !MAP_FIXED case pretty quickly. I would prefer this to be in the changelog rather than/in addition to "It has no user visible effect" which is really vague. Acked-by: Michal Hocko > --- > I made a mistake in a changelog in a previous version of this patch. > I'm Sorry for the confusion. > This patch may be considered to be applied only in case the patch > "[PATCH v2 1/2] mm: fix incorrect behavior when process virtual > address space limit is exceeded" > is not going to be accepted. > > mm/mmap.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 2ce04a6..42a8259 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1551,9 +1551,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr, > * MAP_FIXED may remove pages of mappings that intersects with > * requested mapping. Account for the pages it would unmap. > */ > - if (!(vm_flags & MAP_FIXED)) > - return -ENOMEM; > - > nr_pages = count_vma_pages_range(mm, addr, addr + len); > > if (!may_expand_vm(mm, (len >> PAGE_SHIFT) - nr_pages)) > -- > 2.6.2 > -- Michal Hocko SUSE Labs -- 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