From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55CC8C004D3 for ; Wed, 24 Oct 2018 13:16:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DB5502064C for ; Wed, 24 Oct 2018 13:16:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=thunk.org header.i=@thunk.org header.b="dau/jQwL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DB5502064C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mit.edu Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726735AbeJXVoQ (ORCPT ); Wed, 24 Oct 2018 17:44:16 -0400 Received: from imap.thunk.org ([74.207.234.97]:52676 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726285AbeJXVoQ (ORCPT ); Wed, 24 Oct 2018 17:44:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=thunk.org; s=ef5046eb; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=bBxSB3Vz4tdzpwUC7MA6Ml58QKYOxyWCVP1GvRwfYsc=; b=dau/jQwLkN6wuQgTUvkpNkl8Og zH5tTWa8mClAXqMJdAJJeADvHDnFBQw1RRfmGh4tpKOwx4aqp4Eo4w9EbKraOjKGREhFyZtb6D/90 j025dQxVqvnT5sAB0GqyL4C6QbwTUuk5nP9qrvpDZsxRpNz/YcxDM6WQpusoPdjdtpdg=; Received: from root (helo=callcc.thunk.org) by imap.thunk.org with local-esmtp (Exim 4.89) (envelope-from ) id 1gFJ0e-0007sP-Sx; Wed, 24 Oct 2018 13:15:40 +0000 Received: by callcc.thunk.org (Postfix, from userid 15806) id D180F7A56C1; Wed, 24 Oct 2018 09:15:34 -0400 (EDT) Date: Wed, 24 Oct 2018 09:15:34 -0400 From: "Theodore Y. Ts'o" To: NeilBrown Cc: Andy Lutomirski , Andreas Dilger , Peter Zijlstra , Dmitry Safonov , "H. Peter Anvin" , Denys Vlasenko , Linus Torvalds , Borislav Petkov , Ingo Molnar , Brian Gerst , LKML , Thomas Gleixner , linux-tip-commits@vger.kernel.org, jsimmons@infradead.org Subject: Re: in_compat_syscall() returns from kernel thread for X86_32. Message-ID: <20181024131534.GD11606@thunk.org> Mail-Followup-To: "Theodore Y. Ts'o" , NeilBrown , Andy Lutomirski , Andreas Dilger , Peter Zijlstra , Dmitry Safonov , "H. Peter Anvin" , Denys Vlasenko , Linus Torvalds , Borislav Petkov , Ingo Molnar , Brian Gerst , LKML , Thomas Gleixner , linux-tip-commits@vger.kernel.org, jsimmons@infradead.org References: <1460987025-30360-1-git-send-email-dsafonov@virtuozzo.com> <87h8hkc9fd.fsf@notabene.neil.brown.name> <871s8ndg6a.fsf@notabene.neil.brown.name> <871s8g6roy.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <871s8g6roy.fsf@notabene.neil.brown.name> User-Agent: Mutt/1.10.1 (2018-07-13) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 24, 2018 at 12:47:57PM +1100, NeilBrown wrote: > > I doubt it was copied - more likely independent evolution. > But on reflection, I see that it is probably reasonable that it > shouldn't be used this way - or at all in this context. > I'll try to understand what the issues really are and see if I can > find a solution that doesn't depend on this interface. > Thanks for your help. At least for ext4, the primary problem is that we want to use a 64-bit telldir/seekdir cookie if all 64-bits will make it to user space, and a 32-bit telldir cookie if only 32 bits will make it userspace. This impacts NFS as well because if there are people who are still using NFSv2, which has 32-bit directory offsets, we need to constrain the telldir/seekdir cookies we give to NFS to be a 32 has as opposed to a 64-bit hash. - Ted