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SubjectRe: [patch 3/3 -mmotm] oom: invoke oom killer for __GFP_NOFAIL
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.

Ditto-in-spades cfq-iosched.c. We discussed that recently but I forgot the
upshot. The code and its comment are still in flagrant disagreement?



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