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SubjectRe: [patch 3/3 -mmotm] oom: invoke oom killer for __GFP_NOFAIL
Andrew Morton wrote:
> On Wed, 3 Jun 2009 15:10:38 -0700 (PDT)
> David Rientjes <rientjes@google.com> wrote:
>
>
>> On Tue, 2 Jun 2009, David Rientjes wrote:
>>
>>
>>> With my patch, we kill a memory hogging task that will free some memory so
>>> the allocation will succeed (or multiple tasks if insufficient contiguous
>>> memory is available). Kernel allocations use __GFP_NOFAIL, so the fault
>>> of this memory freeing is entirely on the caller, not the page allocator.
>>>
>>> My preference for handling this is to merge my patch (obviously :), and
>>> then hopefully deprecate __GFP_NOFAIL as much as possible although I don't
>>> suspect it could be eradicated forever.
>>>
>>>
>> I really hope this patch isn't getting dropped because it fixes the
>> possibility that a __GFP_NOFAIL allocation will fail when its definition
>> is to the contrary. Depending on the size of the allocation, that can
>> cause a panic in at least the reiserfs, ntfs, cxgb3, and gfs2 cases.
>>
>> As I mentioned before, it's a noble goal to deprecate __GFP_NOFAIL as much
>> as possible and (at the least) prevent it from trying high-order
>> allocation attempts. The current implementation of the flag is
>> problematic, however, and this patch addresses it by attempting to free
>> some memory when direct reclaim fails.
>>
>>
>
> Sigh, all right, but we suck.
>
> Divy, could we please at least remove __GFP_NOFAIL from
> drivers/net/cxgb? It's really quite inappropriate for a driver to
> assume that core VM can do magic. Drivers should test the return value
> and handle the -ENOMEM in the old-fashioned way, please.
>

We started working on it, and got to eliminate them out of
cxgb3_main.c::init_tp_parity().
We're still looking at eliminating its use in
cxgb3_offload.c::t3_process_tid_release_list().
I'll post the patches as soon as they are ready.

cheers,
Divy



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