From: Andreas Dilger Subject: Re: [PATCH 5/5] ext4: Fix endian problem in MMP initialization Date: Sat, 22 Oct 2011 11:25:31 -0600 Message-ID: <67F2A39D-1E28-4660-8758-0B16DED30096@gmail.com> References: <20111021211759.10784.17257.stgit@elm3c44.beaverton.ibm.com> <20111021211825.10784.97113.stgit@elm3c44.beaverton.ibm.com> Mime-Version: 1.0 (iPhone Mail 8L1) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Cc: Tao Ma , Theodore Tso , "linux-ext4@vger.kernel.org" , linux-kernel To: "Darrick J. Wong" Return-path: Received: from mail-pz0-f42.google.com ([209.85.210.42]:61771 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754055Ab1JVRYk convert rfc822-to-8bit (ORCPT ); Sat, 22 Oct 2011 13:24:40 -0400 In-Reply-To: <20111021211825.10784.97113.stgit@elm3c44.beaverton.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: You can add my Acked-by: Andreas Dilger to this. Cheers, Andreas On 2011-10-21, at 3:18 PM, "Darrick J. Wong" wrote: > As part of startup, the MMP initialization code does this: > > mmp->mmp_seq = seq = cpu_to_le32(mmp_new_seq()); > > Next, mmp->mmp_seq is written out to disk, a delay happens, and then the MMP > block is read back in and the sequence value is tested: > > if (seq != le32_to_cpu(mmp->mmp_seq)) { > /* fail the mount */ > > On a LE system such as x86, the *le32* functions do nothing and this works. > Unfortunately, on a BE system such as ppc64, this comparison becomes: > > if (cpu_to_le32(new_seq) != le32_to_cpu(cpu_to_le32(new_seq)) { > /* fail the mount */ > > Except for a few palindromic sequence numbers, this test always causes the > mount to fail, which makes MMP filesystems generally unmountable on ppc64. The > attached patch fixes this situation. > > Signed-off-by: Darrick J. Wong > --- > fs/ext4/mmp.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > > diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c > index 9bdef3f..a7a4986 100644 > --- a/fs/ext4/mmp.c > +++ b/fs/ext4/mmp.c > @@ -295,7 +295,8 @@ skip: > /* > * write a new random sequence number. > */ > - mmp->mmp_seq = seq = cpu_to_le32(mmp_new_seq()); > + seq = mmp_new_seq(); > + mmp->mmp_seq = cpu_to_le32(seq); > > retval = write_mmp_block(bh); > if (retval) > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html