Messages in this thread | | | Date | Tue, 25 Oct 2011 09:35:05 -0400 | From | Ted Ts'o <> | Subject | Re: [PATCH 5/5] ext4: Fix endian problem in MMP initialization |
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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
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