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

[Divy Le Ray]

Andrew Morton wrote:
> On Wed, 3 Jun 2009 15:10:38 -0700 (PDT)
> David Rientjes <rientjes@xxxxxxxxxx> 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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