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authorDarrick J. Wong <djwong@us.ibm.com>2011-10-18 10:53:51 -0400
committerTheodore Ts'o <tytso@mit.edu>2011-10-18 10:53:51 -0400
commitf6f96fdb8c2779f9bd8ed7b0b08405b4439c982b (patch)
tree310c22fa079a169a824910bd3c3b13464a22c12c /fs
parentbdfc230f33a9dab316dcb6be4696ae59e1562e3c (diff)
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blackbird-op-linux-f6f96fdb8c2779f9bd8ed7b0b08405b4439c982b.zip
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 <djwong@us.ibm.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs')
-rw-r--r--fs/ext4/mmp.c3
1 files changed, 2 insertions, 1 deletions
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)
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