From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753047AbXCPHit (ORCPT ); Fri, 16 Mar 2007 03:38:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753052AbXCPHis (ORCPT ); Fri, 16 Mar 2007 03:38:48 -0400 Received: from smtp104.mail.mud.yahoo.com ([209.191.85.214]:41710 "HELO smtp104.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752966AbXCPHis (ORCPT ); Fri, 16 Mar 2007 03:38:48 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=2cYOd2/SBqYKazMipLy+IpmwN+m/qL2/Z7qwQxzKQatlzSqv9XkNBQ7yAdMXAXDR9iXFCEKjwRivnbAaitsX9DHu3pnaYL3vYOb8mExWPAeZY7rpG+AMvBFUY+yoBDpj4haI70Uo4qRyp55Cv+zhE4xgRkTBrpGiC8fADFqNsf8= ; X-YMail-OSG: pvxxAmoVM1lXi4_ydmvbWJScsd1Ykx9jtxJmujrEgSNKz2BMbPsHcvcka2GTjPG8cz_039gvszDCMLA92yaJ5XS3zEZpnQMFc3lNwcXQRq4ICvMktm3Vz2LlHq5HEcZL3pKsdHDlpFmJeUE- Message-ID: <45FA4984.9000506@yahoo.com.au> Date: Fri, 16 Mar 2007 18:38:44 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Pekka J Enberg CC: akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] revoke: misc fixes References: <45FA458C.8050605@yahoo.com.au> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Pekka J Enberg wrote: > Pekka J Enberg wrote: > >>> /* >>>- * Not holding ->mmap_sem here. >>>+ * Not holding ->mmap_sem here but we must watch out for page >>>+ * faults and after the shared mappings have been taken down >>>+ * and sys_mmap() trying to remap the revoked range. >>> */ >>> vma->vm_flags |= VM_REVOKED; >>> smp_mb(); >>>@@ -455,7 +457,7 @@ int err = 0; > > > On Fri, 16 Mar 2007, Nick Piggin wrote: > >>You're still modifying vm_flags without down_write mmap_sem, so this will >>corrupt vm_flags. > > > Uhm, you're right, two concurrent writes and we can lose some bits so a > barrier doesn't work. Too bad as we're under mapping->i_mmap_lock here and > thus cannot take ->mmap_sep... > Could you try something like walk the i_mmap lists to find mms with vmas that haven't need revoking, then each time you find one, take a ref on the mm, drop i_mmap_lock, take mmap_sem, and walk all its vmas looking for any that reference the inode? Bit of a roundabout way to go, but it might work. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com