Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752212AbcDZM4h (ORCPT ); Tue, 26 Apr 2016 08:56:37 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:34363 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751507AbcDZM4f (ORCPT ); Tue, 26 Apr 2016 08:56:35 -0400 From: Michal Hocko To: , Andrew Morton Cc: LKML , Michal Hocko , Oleg Nesterov , "Kirill A. Shutemov" , Konstantin Khlebnikov , Andrea Arcangeli , Alexander Viro Subject: [PATCH 03/18] mm: make vm_munmap killable Date: Tue, 26 Apr 2016 14:56:10 +0200 Message-Id: <1461675385-5934-4-git-send-email-mhocko@kernel.org> X-Mailer: git-send-email 2.8.0.rc3 In-Reply-To: <1461675385-5934-1-git-send-email-mhocko@kernel.org> References: <1461675385-5934-1-git-send-email-mhocko@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1637 Lines: 47 From: Michal Hocko Almost all current users of vm_munmap are ignoring the return value and so they do not handle potential error. This means that some VMAs might stay behind. This patch doesn't try to solve those potential problems. Quite contrary it adds a new failure mode by using down_write_killable in vm_munmap. This should be safer than other failure modes, though, because the process is guaranteed to die as soon as it leaves the kernel and exit_mmap will clean the whole address space. This will help in the OOM conditions when the oom victim might be stuck waiting for the mmap_sem for write which in turn can block oom_reaper which relies on the mmap_sem for read to make a forward progress and reclaim the address space of the victim. Cc: Oleg Nesterov Cc: "Kirill A. Shutemov" Cc: Konstantin Khlebnikov Cc: Andrea Arcangeli Cc: Alexander Viro Signed-off-by: Michal Hocko --- mm/mmap.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 1d229487dab1..032605bda665 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2494,11 +2494,9 @@ int vm_munmap(unsigned long start, size_t len) int ret; struct mm_struct *mm = current->mm; - /* - * XXX convert to down_write_killable as soon as all users are able - * to handle the error. - */ - down_write(&mm->mmap_sem); + if (down_write_killable(&mm->mmap_sem)) + return -EINTR; + ret = do_munmap(mm, start, len); up_write(&mm->mmap_sem); return ret; -- 2.8.0.rc3