From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f200.google.com (mail-qt0-f200.google.com [209.85.216.200]) by kanga.kvack.org (Postfix) with ESMTP id 124DB6B02F4 for ; Tue, 15 Aug 2017 22:18:23 -0400 (EDT) Received: by mail-qt0-f200.google.com with SMTP id u11so12647241qtu.10 for ; Tue, 15 Aug 2017 19:18:23 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id s3si9809861qtg.497.2017.08.15.19.18.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Aug 2017 19:18:22 -0700 (PDT) Message-ID: <1502849899.6577.66.camel@redhat.com> Subject: Re: [PATCH 2/2] mm,fork: introduce MADV_WIPEONFORK From: Rik van Riel Date: Tue, 15 Aug 2017 22:18:19 -0400 In-Reply-To: <20170815155114.ff9f4164eed28bf02db48fbb@linux-foundation.org> References: <20170811212829.29186-1-riel@redhat.com> <20170811212829.29186-3-riel@redhat.com> <20170815155114.ff9f4164eed28bf02db48fbb@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-kernel@vger.kernel.org, mhocko@kernel.org, mike.kravetz@oracle.com, linux-mm@kvack.org, fweimer@redhat.com, colm@allcosts.net, keescook@chromium.org, luto@amacapital.net, wad@chromium.org, mingo@kernel.org, kirill@shutemov.name, dave.hansen@intel.com, linux-api@vger.kernel.org, torvalds@linux-foundation.org, willy@infradead.org On Tue, 2017-08-15 at 15:51 -0700, Andrew Morton wrote: > On Fri, 11 Aug 2017 17:28:29 -0400 riel@redhat.com wrote: > > > A further complication is the proliferation of clone flags, > > programs bypassing glibc's functions to call clone directly, > > and programs calling unshare, causing the glibc pthread_atfork > > hook to not get called. > > > > It would be better to have the kernel take care of this > > automatically. > > I'll add "The patch also adds MADV_KEEPONFORK, to undo the effects of > a > prior MADV_WIPEONFORK." here. > > I guess it isn't worth mentioning that these things can cause VMA > merges and splits.A That's the same as every other Linux specific madvise operation. > > --- a/mm/madvise.c > > +++ b/mm/madvise.c > > @@ -80,6 +80,17 @@ static long madvise_behavior(struct > > vm_area_struct *vma, > > A } > > A new_flags &= ~VM_DONTCOPY; > > A break; > > + case MADV_WIPEONFORK: > > + /* MADV_WIPEONFORK is only supported on anonymous > > memory. */ > > + if (vma->vm_file || vma->vm_flags & VM_SHARED) { > > + error = -EINVAL; > > + goto out; > > + } > > + new_flags |= VM_WIPEONFORK; > > + break; > > + case MADV_KEEPONFORK: > > + new_flags &= ~VM_WIPEONFORK; > > + break; > > A case MADV_DONTDUMP: > > A new_flags |= VM_DONTDUMP; > > A break; > > It seems odd to permit MADV_KEEPONFORK against other-than-anon vmas? Given that the only way to set VM_WIPEONFORK is through MADV_WIPEONFORK, calling MADV_KEEPONFORK on an other-than-anon vma would be equivalent to a noop. If new_flags == vma->vm_flags, madvise_behavior() will immediately exit. -- 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