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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 1DCBCC433DF for ; Tue, 14 Jul 2020 03:41:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E2E1821D93 for ; Tue, 14 Jul 2020 03:41:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594698074; bh=SPL3nkj9HvC2j7rtwl00nNXwS53s+StgAz1Rltp3OXE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=W2xgGeYSQPqcNMcQHRwk9tXg9iIrQxi6f+NlLx2PJPyYwbdBXgeiLWA3QEcSeiany MGuMLMKyPzJdwpefec20m1wO/hJCRzI6Cbx1ivdH15M8DBULdYzcntwcA13HD4LELK 75OkQ/KcuOiC1kIjWUkblZKa7l+qsnAYxNVL39fM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726777AbgGNDlN (ORCPT ); Mon, 13 Jul 2020 23:41:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:51326 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726432AbgGNDlN (ORCPT ); Mon, 13 Jul 2020 23:41:13 -0400 Received: from sol.localdomain (c-107-3-166-239.hsd1.ca.comcast.net [107.3.166.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 67C8D20890; Tue, 14 Jul 2020 03:41:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594698072; bh=SPL3nkj9HvC2j7rtwl00nNXwS53s+StgAz1Rltp3OXE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Pn4xLHed5UErZazjYs75fzvgnaYZ3py3NH+VTIX724EC9TUqwdfrEv0jCtI5x3vj2 EcUQBE7VdW1zx031C74H8IiVcL3J+EpURqyQwsT7kCDHC7vukx4ZThuUXuj41Abqg/ EdHFmTdurMMLft9g//TwoWhWD6R5YzJPHJLQEJCw= Date: Mon, 13 Jul 2020 20:41:11 -0700 From: Eric Biggers To: Hillf Danton Cc: syzbot , akpm@linux-foundation.org, arve@android.com, christian@brauner.io, devel@driverdev.osuosl.org, gregkh@linuxfoundation.org, hughd@google.com, joel@joelfernandes.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, maco@android.com, syzkaller-bugs@googlegroups.com, tkjos@android.com, Markus Elfring Subject: Re: possible deadlock in shmem_fallocate (4) Message-ID: <20200714034111.GD1696@sol.localdomain> References: <0000000000000b5f9d059aa2037f@google.com> <20200714033252.8748-1-hdanton@sina.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200714033252.8748-1-hdanton@sina.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 14, 2020 at 11:32:52AM +0800, Hillf Danton wrote: > > Add FALLOC_FL_NOBLOCK and on the shmem side try to lock inode upon the > new flag. And the overall upside is to keep the current gfp either in > the khugepaged context or not. > > --- a/include/uapi/linux/falloc.h > +++ b/include/uapi/linux/falloc.h > @@ -77,4 +77,6 @@ > */ > #define FALLOC_FL_UNSHARE_RANGE 0x40 > > +#define FALLOC_FL_NOBLOCK 0x80 > + You can't add a new UAPI flag to fix a kernel-internal problem like this. - Eric