xfs: fix log CRC mismatches between i386 and other architectures

xfs: fix log CRC mismatches between i386 and other architectures

[ Upstream commit e747883c7d7306acb4d683038d881528fbfbe749 ]

When mounting file systems with a log that was dirtied on i386 on
other architectures or vice versa, log recovery is unhappy:

[   11.068052] XFS (vdb): Torn write (CRC failure) detected at log block 0x2. Truncating head block from 0xc.

This is because the CRCs generated by i386 and other architectures
always diff.  The reason for that is that sizeof(struct xlog_rec_header)
returns different values for i386 vs the rest (324 vs 328), because the
struct is not sizeof(uint64_t) aligned, and i386 has odd struct size
alignment rules.

This issue goes back to commit 13cdc853c519 ("Add log versioning, and new
super block field for the log stripe") in the xfs-import tree, which
adds log v2 support and the h_size field that causes the unaligned size.
At that time it only mattered for the crude debug only log header
checksum, but with commit 0e446be44806 ("xfs: add CRC checks to the log")
it became a real issue for v5 file system, because now there is a proper
CRC, and regular builds actually expect it match.

Fix this by allowing checksums with and without the padding.

Fixes: 0e446be44806 ("xfs: add CRC checks to the log")
Cc: <stable@vger.kernel.org> # v3.8
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
[ Adjust context and filenames ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>