Re: Propagating GFP_NOFS inside __vmalloc()

[David Rientjes <rientjes@google.com>]

On Wed, 17 Nov 2010, Andreas Dilger wrote:

> >> - avoid doing anything other than GFP_KERNEL allocations for __vmalloc():
> >>   the only current users are gfs2, ntfs, and ceph (the page allocator
> >>   __vmalloc() can be discounted since it's done at boot and GFP_ATOMIC
> >>   here has almost no chance of failing since the size is determined based 
> >>   on what is available).
> > 
> > ^^ this
> > 
> > Using vmalloc anywhere is lame.
> 
> I agree.  What we really want is 1MB kmalloc() to work...  :-/
> 

Order-8 allocations are already have a higher liklihood of succeeding 
because of memory compaction, which was explicitly targeted to aid in 
order-9 hugepage allocations.  The problem is that it's useless for 
GFP_NOFS.

I think removing gfp_t arguments from all of the public vmalloc interface 
will inevitably be where we go with this and everything will assume 
GFP_KERNEL | __GFP_HIGHMEM.

If you _really_ need 1MB of physically contiguous memory, then you'll need 
to find a way to do it in a reclaimable context.  If we actually can 
remove the dependency that gfs2, ntfs, and ceph have in the kernel.org 
kernel, then this support may be pulled out from under you; the worst-case 
scenario for Lustre is that you'll have to modify the callchains like I 
suggested in my original email to pass the gfp mask all the way down to 
the pte allocators if you can't find a way to do it under GFP_KERNEL.

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