[dm-crypt] writing greater than 1GB of data through the mapper to a file hangs kernel 3.2.x

.. ink .. mhogomchungu at gmail.com
Thu Jul 5 23:03:40 CEST 2012


> I am using pclinuxos and "uname -a" gives:
> Linux mtz 3.2.18-pclos2.bfs #1 SMP PREEMPT Thu May 24 04:44:50 CEST
> 2012 i686 i686 i386 GNU/Linux
>
> Using this kernel version:
>
> i created a 2GB file using dd, then i opened a plain mapper on the
> file and then attempted to write 1GB of data through the mapper using
> dd and the system lock up. I tried it 3 times and it lock up 3 times.
>
> writing 100MB  or smaller amount of data does not hang the system.It
> seem the lock up occurs when a certain number of data is passed.
>
> is this problem known?

just to add to above with test results:
i created a 2GB file,  then run the following commands to see where it
would lock up

[root at mtz ink]# cryptsetup create zzz zzz
[root at mtz ink]# dd if=/dev/zero of=/dev/mapper/zzz  bs=1024 count=110K
112640+0 records in
112640+0 records out
115343360 bytes (115 MB) copied, 7.15232 s, 16.1 MB/s
[root at mtz ink]# dd if=/dev/zero of=/dev/mapper/zzz  bs=1024 count=140K
143360+0 records in
143360+0 records out
146800640 bytes (147 MB) copied, 4.80232 s, 30.6 MB/s
[root at mtz ink]# dd if=/dev/zero of=/dev/mapper/zzz  bs=1024 count=200K
204800+0 records in
204800+0 records out
209715200 bytes (210 MB) copied, 9.2493 s, 22.7 MB/s
[root at mtz ink]# dd if=/dev/zero of=/dev/mapper/zzz  bs=1024 count=500K
512000+0 records in
512000+0 records out
524288000 bytes (524 MB) copied, 36.333 s, 14.4 MB/s
[root at mtz ink]# dd if=/dev/zero of=/dev/mapper/zzz  bs=1024 count=800K
819200+0 records in
819200+0 records out
838860800 bytes (839 MB) copied, 205.896 s, 4.1 MB/s

The last one locked the system couple of times but it managed to succeed.

I then attempted to write 900MB to /dev/mapper/zzz and the system
locked up and had to hard power down two hours later..

Will appreciate if some body could do the test locally with the kernel
they are using to help me pin down the problem. Would like to avoid
first time experience like the one reported here in the second
paragraph: http://www.pclinuxos.com/forum/index.php/topic,106847.msg912803.html#msg912803


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