Re: [LKP] [mm] cc87317726f: WARNING: CPU: 0 PID:1atdrivers/iommu/io-pgtable-arm.c:413 __arm_lpae_unmap+0x341/0x380()

[Tetsuo Handa]

Michal Hocko wrote:
> On Fri 20-03-15 22:34:21, Tetsuo Handa wrote:
> > 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.
> 
> I guess you meant __GFP_NOFAIL?
> 
No. btrfs's selftest (which is not using __GFP_NOFAIL) is already looping
forever. If we want to avoid btrfs's selftest from looping forever, btrfs
needs __GFP_NORETRY than __GFP_NOFAIL (until we establish a way to safely
allow small allocations to fail).
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