The linux bitset operators (test_bit, set_bit etc) work on arrays of "unsigned long". dm-log uses such bitsets but treats them as arrays of uint32_t, only allocating and zeroing a multiple of 4 bytes (as 'clean_bits' is a uint32_t). The patch below fixes this problem. The problem is specific to 64-bit big endian machines such as s390x or ppc-64 and can prevent pvmove terminating. In the simplest case, if "region_count" were (say) 30, then bitset_size (below) would be 4 and bitset_uint32_count would be 1. Thus the memory for this butset, after allocation and zeroing would be 0 0 0 0 X X X X On a bigendian 64bit machine, bit 0 for this bitset is in the 8th byte! (and every bit that dm-log would use would be in the X area). 0 0 0 0 X X X X ^ here which hasn't been cleared properly. As the dm-raid1 code only syncs and counts regions which have a 0 in the 'sync_bits' bitset, and only finishes when it has counted high enough, a large number of 1's among those 'X's will cause the sync to not complete. It is worth noting that the code uses the same bitsets for in-memory and on-disk logs. As these bitsets are host-endian and host-sized, this means that they cannot safely be moved between computers with different architectures. Signed-off-by: Neil Brown <neilb> dm-log-bitset-fix.patch
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2006-0132.html