Message ID | 20110930194900.GY12086@tux1.beaverton.ibm.com |
---|---|
State | Accepted, archived |
Headers | show |
On 2011-09-30, at 1:49 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. > > (This fix came up while testing the metadata checksumming patchset) Thanks also for the catch, you are completely right. We've never run this code on a big-endian system in all the years we had it. > 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) > -- > 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 Cheers, Andreas -- 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
On Fri, Sep 30, 2011 at 12:49:00PM -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. > > (This fix came up while testing the metadata checksumming patchset) > > Signed-off-by: Darrick J. Wong <djwong@us.ibm.com> Applied, thanks. - Ted -- 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
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)
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. (This fix came up while testing the metadata checksumming patchset) Signed-off-by: Darrick J. Wong <djwong@us.ibm.com> --- fs/ext4/mmp.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) -- 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