From: Ted Ts'o <tytso@mit.edu>
To: "Darrick J. Wong" <djwong@us.ibm.com>
Cc: Tao Ma <tm@tao.ma>,
linux-ext4@vger.kernel.org,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 5/5] ext4: Fix endian problem in MMP initialization
Date: Tue, 25 Oct 2011 09:35:05 -0400 [thread overview]
Message-ID: <20111025133505.GL31921@thunk.org> (raw)
In-Reply-To: <20111021211825.10784.97113.stgit@elm3c44.beaverton.ibm.com>
On Fri, Oct 21, 2011 at 02:18:25PM -0700, 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 <djwong@us.ibm.com>
Thanks, this is already in the ext4 tree, although not yet in the
master branch (just the dev branch).
- Ted
next prev parent reply other threads:[~2011-10-25 13:35 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-21 21:17 [PATCH 1/5] ext4: ext4_dx_add_entry should dirty directory metadata with the directory inode Darrick J. Wong
2011-10-21 21:18 ` [PATCH 2/5] ext4: ext4_rename should dirty dir_bh with the correct directory Darrick J. Wong
2011-10-25 13:08 ` Ted Ts'o
2011-10-21 21:18 ` [PATCH 3/5] ext4: ext4_mkdir should dirty dir_block with the parent inode Darrick J. Wong
2011-10-25 13:09 ` Ted Ts'o
2011-10-21 21:18 ` [PATCH 4/5] ext4: Prevent stack overrun in ext4_file_open when recording last known mountpoint Darrick J. Wong
2011-10-25 13:22 ` Ted Ts'o
2011-10-21 21:18 ` [PATCH 5/5] ext4: Fix endian problem in MMP initialization Darrick J. Wong
2011-10-22 17:25 ` Andreas Dilger
2011-10-25 13:35 ` Ted Ts'o [this message]
2011-10-25 13:13 ` [PATCH 1/5] ext4: ext4_dx_add_entry should dirty directory metadata with the directory inode Ted Ts'o
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