linux-kernel - Re: [PATCH] slub: fix a memory leak in get_partial

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Date:	Tue, 15 May 2012 12:10:47 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Joonsoo Kim <js1304@...il.com>
Cc:	Pekka Enberg <penberg@...nel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] slub: fix a memory leak in get_partial_node()

On Wed, May 16, 2012 at 04:01:38AM +0900, Joonsoo Kim wrote:
> In the case which is below,
> 
> 1. acquire slab for cpu partial list
> 2. free object to it by remote cpu
> 3. page->freelist = t
> 
> then memory leak is occurred.
> 
> Change acquire_slab() not to zap freelist when it works for cpu partial list.
> I think it is a sufficient solution for fixing a memory leak.
> 
> Below is output of 'slabinfo -r kmalloc-256'
> when './perf stat -r 30 hackbench 50 process 4000 > /dev/null' is done.
> 
> ***Vanilla***
> Sizes (bytes)     Slabs              Debug                Memory
> ------------------------------------------------------------------------
> Object :     256  Total  :     468   Sanity Checks : Off  Total: 3833856
> SlabObj:     256  Full   :     111   Redzoning     : Off  Used : 2004992
> SlabSiz:    8192  Partial:     302   Poisoning     : Off  Loss : 1828864
> Loss   :       0  CpuSlab:      55   Tracking      : Off  Lalig:       0
> Align  :       8  Objects:      32   Tracing       : Off  Lpadd:       0
> 
> ***Patched***
> Sizes (bytes)     Slabs              Debug                Memory
> ------------------------------------------------------------------------
> Object :     256  Total  :     300   Sanity Checks : Off  Total: 2457600
> SlabObj:     256  Full   :     204   Redzoning     : Off  Used : 2348800
> SlabSiz:    8192  Partial:      33   Poisoning     : Off  Loss :  108800
> Loss   :       0  CpuSlab:      63   Tracking      : Off  Lalig:       0
> Align  :       8  Objects:      32   Tracing       : Off  Lpadd:       0
> 
> Total and loss number is the impact of this patch.
> 
> Signed-off-by: Joonsoo Kim <js1304@...il.com>

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read Documentation/stable_kernel_rules.txt
for how to do this properly.

</formletter>
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