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Author SHA1 Message Date
Alasdair G Kergon
0e56822d30 [PATCH] device-mapper: mirror log bitset fix
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

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-22 09:14:31 -08:00
Linus Torvalds
1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00