Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751303Ab3FHGNI (ORCPT ); Sat, 8 Jun 2013 02:13:08 -0400 Received: from smtp.gentoo.org ([140.211.166.183]:52960 "EHLO smtp.gentoo.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750911Ab3FHGNG (ORCPT ); Sat, 8 Jun 2013 02:13:06 -0400 Date: Sat, 8 Jun 2013 09:11:14 +0300 From: Sergei Trofimovich To: gentoo-dev@lists.gentoo.org Cc: ryao@gentoo.org, Kernel development list , kernel@gentoo.org, gentooligan@gmail.com Subject: Re: [gentoo-dev] dm-crypt reordering BIOs across barriers? Message-ID: <20130608091114.441c5f17@sf> In-Reply-To: <51B2A955.4010906@gentoo.org> References: <51B2A955.4010906@gentoo.org> Reply-To: gentoo-dev@lists.gentoo.org X-Mailer: Claws Mail 3.9.0 (GTK+ 2.24.17; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/fo7M09A2dxvn/n99HU_TveV"; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1635 Lines: 46 --Sig_/fo7M09A2dxvn/n99HU_TveV Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Fri, 07 Jun 2013 23:47:33 -0400 Richard Yao wrote: > When you use dm-crypt, block IO requests to a dm-* device will invoke > dm_request_fn() -> map_request() -> crypt_map(). If a BIO is a write > barrier, crypt_map() will return DM_MAPIO_REMAPPED to map_request(), > which will immediately queue it to the device. >=20 > If a few dozen IOs are queued in rapid succession with multiple write > barriers, all write barriers will be executed before any actual write > BIOs occur because the write IOs will be processed asynchronously in a > work queue. Since the barriers will be long gone by the time the write > IOs are queued, they can be queued in any order. >=20 > Am I misunderstanding this or is dm-crypt ignoring proper write barrier > semantics? >=20 http://www.saout.de/pipermail/dm-crypt/2012-April/002441.html http://lwn.net/Articles/400541/ --=20 Sergei --Sig_/fo7M09A2dxvn/n99HU_TveV Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) iEYEARECAAYFAlGyywYACgkQcaHudmEf86qSNwCePybnYkljHZgbPS2hTdks3mOp ZUAAn2z23+P8ndmybC4CF/QgXTPluT4t =QXSG -----END PGP SIGNATURE----- --Sig_/fo7M09A2dxvn/n99HU_TveV-- -- 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/