From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 7D64B6B0047 for ; Fri, 8 Jan 2010 17:05:33 -0500 (EST) From: David Howells Subject: [PATCH 3/6] NOMMU: Remove a superfluous check of vm_region::vm_usage Date: Fri, 08 Jan 2010 22:05:28 +0000 Message-ID: <20100108220527.23489.91998.stgit@warthog.procyon.org.uk> In-Reply-To: <20100108220516.23489.11319.stgit@warthog.procyon.org.uk> References: <20100108220516.23489.11319.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: viro@ZenIV.linux.org.uk, vapier@gentoo.org, lethal@linux-sh.org Cc: dhowells@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: In split_vma(), there's no need to check if the VMA being split has a region that's in use by more than one VMA because: (1) The preceding test prohibits splitting of non-anonymous VMAs and regions (eg: file or chardev backed VMAs). (2) Anonymous regions can't be mapped multiple times because there's no handle by which to refer to the already existing region. (3) If a VMA has previously been split, then the region backing it has also been split into two regions, each of usage 1. Signed-off-by: David Howells --- mm/nommu.c | 7 +++---- 1 files changed, 3 insertions(+), 4 deletions(-) diff --git a/mm/nommu.c b/mm/nommu.c index 5e39294..d6dd656 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1441,10 +1441,9 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma, kenter(""); - /* we're only permitted to split anonymous regions that have a single - * owner */ - if (vma->vm_file || - vma->vm_region->vm_usage != 1) + /* we're only permitted to split anonymous regions (these should have + * only a single usage on the region) */ + if (vma->vm_file) return -ENOMEM; if (mm->map_count >= sysctl_max_map_count) -- 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