Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760203AbYFRC1d (ORCPT ); Tue, 17 Jun 2008 22:27:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759527AbYFRC1X (ORCPT ); Tue, 17 Jun 2008 22:27:23 -0400 Received: from out3.smtp.messagingengine.com ([66.111.4.27]:40231 "EHLO out3.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759495AbYFRC1X (ORCPT ); Tue, 17 Jun 2008 22:27:23 -0400 X-Greylist: delayed 356 seconds by postgrey-1.27 at vger.kernel.org; Tue, 17 Jun 2008 22:27:23 EDT Date: Wed, 18 Jun 2008 12:27:12 +1000 From: Bron Gondwana To: Linus Torvalds Cc: Bron Gondwana , Linux Kernel Mailing List , Nick Piggin , Andrew Morton , Rob Mueller , Andi Kleen , Ingo Molnar Subject: Re: BUG: mmapfile/writev spurious zero bytes (x86_64/not i386, bisected, reproducable) Message-ID: <20080618022712.GB1383@brong.net> References: <1213682410.13174.1258837181@webmail.messagingengine.com> <1213682570.13708.1258839317@webmail.messagingengine.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: brong.net User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1628 Lines: 39 On Tue, Jun 17, 2008 at 02:20:49PM -0700, Linus Torvalds wrote: > > > On Tue, 17 Jun 2008, Linus Torvalds wrote: > > > > Hmm. Something like this *may* salvage it. > > > > Untested, so far (I'll reboot and test soon enough), but even if it fixes > > things, it's not really very good. > > Ok, so I just rebooted with this, and it does indeed fix the bug. > > I'd be happier with a more complete fix (ie being byte-accurate and > actually doing the partial copy when it hits a fault in the middle), but > this seems to be the minimal fix, and at least fixes the totally bogus > return values from the x86-64 __copy_user*() functions. > > Not that I checked that I got _all_ cases correct (and maybe there are > other versions of __copy_user that I missed entirely), but Bron's > test-case at least seems to work properly for me now. > > Bron? If you have a more complete test-suite (ie the real-world case that > made you find this), it would be good to verify the whole thing. I have a real world test case using "cyr_dbtool" from Cyrus 2.3.12 on a known-bug-inducing piece of data (the key and value sizes in the example code were taken from that. Indeed, the example code started off building byte-for-byte identical files, then I changed it to write only a single character across the entire key and value so the hexdump was shorter) I'll give it a go. Bron. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/