From: Darrick J. Wong Date: Tue, 18 Oct 2011 14:53:51 +0000 (-0400) Subject: ext4: Fix comparison endianness problem in MMP initialization X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=f6f96fdb8c2779f9bd8ed7b0b08405b4439c982b;p=openwrt%2Fstaging%2Fblogic.git ext4: Fix comparison endianness problem in MMP initialization 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 Signed-off-by: "Theodore Ts'o" --- diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c index 6b327423e622..7ea4ba4eff2a 100644 --- a/fs/ext4/mmp.c +++ b/fs/ext4/mmp.c @@ -296,7 +296,8 @@ 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)