From: Eric Gouriou Subject: Re: [PATCH 1/2] ext4: remove a wrong BUG_ON in ext4_ext_convert_to_initialized Date: Mon, 12 Dec 2011 16:01:56 -0800 Message-ID: References: <1323235287-29806-1-git-send-email-xiaoqiangnk@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "linux-ext4@vger.kernel.org" , "achender@linux.vnet.ibm.com" , "hughd@google.com" , "tytso@mit.edu" To: Yongqiang Yang Return-path: Received: from mail-qy0-f174.google.com ([209.85.216.174]:41716 "EHLO mail-qy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753709Ab1LMAB6 convert rfc822-to-8bit (ORCPT ); Mon, 12 Dec 2011 19:01:58 -0500 Received: by qcqz2 with SMTP id z2so4091042qcq.19 for ; Mon, 12 Dec 2011 16:01:57 -0800 (PST) In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: [Yet another resend, without HTML and _with_ the list CC'ed. Apologies for the spam] On Fri, Dec 9, 2011 at 19:36, Yongqiang Yang wr= ote: > > > On Saturday, December 10, 2011, Eric Gouriou wr= ote: >> On Tue, Dec 6, 2011 at 21:21, Yongqiang Yang >> wrote: >>> If a file is fallocated on a hole, map->m_lblk + map->m_len may be >>> greater >>> than ee_block + ee_len. >> >> Could you please detail a scenario that leads to this check being in= valid? >> As I'm to blame for the faulty BUG_ON I'd like to use this as an >> opportunity >> to get properly edified. > It's easy to reproduce, I think. =C2=A0 Just need to write beyond fal= located > blocks, write back would submit a request to ext4_map_blocks with blo= cks > part of which are fallocated while other part of which are not, then = the > bug-on would happen. Thanks, this makes sense. > > I met the bug_on during fsx and after the patch applied it works norm= al. > > I think Allison also tested with this patch. > > Yongqiang.. > >> >>> Signed-off-by: Yongqiang Yang Reviewed-by: Eric Gouriou Thanks - Eric >>> --- >>> =C2=A0fs/ext4/extents.c | =C2=A0 =C2=A01 - >>> =C2=A01 files changed, 0 insertions(+), 1 deletions(-) >>> >>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c >>> index 6f0300e..29bb629 100644 >>> --- a/fs/ext4/extents.c >>> +++ b/fs/ext4/extents.c >>> @@ -2943,7 +2943,6 @@ static int ext4_ext_convert_to_initialized(ha= ndle_t >>> *handle, >>> =C2=A0 =C2=A0 =C2=A0 =C2=A0/* Pre-conditions */ >>> =C2=A0 =C2=A0 =C2=A0 =C2=A0BUG_ON(!ext4_ext_is_uninitialized(ex)); >>> =C2=A0 =C2=A0 =C2=A0 =C2=A0BUG_ON(!in_range(map->m_lblk, ee_block, = ee_len)); >>> - =C2=A0 =C2=A0 =C2=A0 BUG_ON(map->m_lblk + map->m_len > ee_block += ee_len); >> >> For a bit I thought this would break the fast path logic, however it= gets >> protected by the checks marked /*L1*/ and /*L2*/ since m_lblk =3D=3D= ee_block >> (L1) and m_len < ee_len (L2). >> >> =C2=A0Regards - Eric >> >>> >>> =C2=A0 =C2=A0 =C2=A0 =C2=A0/* >>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 * Attempt to transfer newly initialized= blocks from the currently >>> -- >>> 1.7.5.1 >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-ext= 4" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at =C2=A0http://vger.kernel.org/majordomo-info.= html >> > > -- > Best Wishes > Yongqiang Yang > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html