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Subject: Re: [LKP] [mm] cc87317726f: WARNING: CPU: 0 PID: 1atdrivers/iommu/io-pgtable-arm.c:413 __arm_lpae_unmap+0x341/0x380()
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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Message-Id: <201503202234.HIA00180.MQVLSFFtHOOFJO@I-love.SAKURA.ne.jp>
Date: Fri, 20 Mar 2015 22:34:21 +0900
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To: ying.huang@intel.com
Cc: hannes@cmpxchg.org, torvalds@linux-foundation.org, mhocko@suse.cz, rientjes@google.com, akpm@linux-foundation.org, david@fromorbit.com, linux-kernel@vger.kernel.org, lkp@01.org, linux-mm@kvack.org

Huang Ying wrote:
> > > BTW: the test is run on 32 bit system.
> > 
> > That sounds like the cause of your problem. The system might be out of
> > address space available for the kernel (only 1GB if x86_32). You should
> > try running tests on 64 bit systems.
> 
> We run test on 32 bit and 64 bit systems.  Try to catch problems on both
> platforms.  I think we still need to support 32 bit systems?

Yes, testing on both platforms is good. But please read
http://lwn.net/Articles/627419/ , http://lwn.net/Articles/635354/ and
http://lwn.net/Articles/636017/ . Then please add __GFP_NORETRY to memory
allocations in btrfs code if it is appropriate.

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