Messages in this thread Patch in this message |  | | | Subject | [PATCH 05/28] ext4: Fix endian problem in MMP initialization | | From | "Darrick J. Wong" <> | | Date | Sat, 08 Oct 2011 00:54:16 -0700 |
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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> --- 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)
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