[BUG] memory leak in dm

[Kristof Provost <Kristof@provost-engineering.be>]

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Hi,

I'm seeing a serious memory leak whenever I use my /home partition.
It's an encrypted partition using dm-crypt. Simply running 
'stress -d 5' is enough to exhaust the memory in a few minutes.

When I stop 'stress' the memory isn't returned.
This doesn't seem to happen when I run stress on a normal (no dm and 
no encryption) partition.

Here's the output of 'free -m' before and after 'stress -d 1 -t 5'
Before:
             total       used       free     shared    buffers     cached
Mem:           751        584        167          0         14        235
-/+ buffers/cache:        334        416
Swap:          980          0        980

After:
             total       used       free     shared    buffers     cached
Mem:           751        619        131          0         12        169
-/+ buffers/cache:        437        313
Swap:          980          0        980

That's 100Mb of RAM gone in 5 seconds.  

I'm using a standard x86 centrino laptop.
The log files don't reveal anything suspicious.

git bisect tells me it started in one of these commits:
d24517d793f21edab1a411da95f2c45cb88a84aa, 
5bb23a688b2de23d7765a1dd439d89c038378978 and 
9cc54d40b8ca01fcefc9151044b6996565061d90. 

The bug is still present in the last version of Linus' tree
(65a6ec0d72a07f16719e9b7a96e1c4bae044b591)

Let me know if I can provide more information.

Regards,
Kristof

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