Re: [patch 2/8] mm: merge populate and nopage into fault (fixes nonlinear)

[Nick Piggin <npiggin@suse.de>]

On Thu, May 24, 2007 at 09:37:19AM +1000, Benjamin Herrenschmidt wrote:
> On Fri, 2007-05-18 at 08:11 -0700, Linus Torvalds wrote:
> 
> > Also, the commentary says that you're planning on replacing "nopfn" too, 
> > which means that returning a "struct page *" is wrong. So the patch is
> > introducing a new interface that is already known to be broken. 
> 
> Agreed.

Yep, I will change it to return the fault type. This makes page_mkwrite
merge cleaner too.


> >  - "struct fault_data" is a stupid name. Of *course* it is data: it's a 
> >    struct. It can't be code. But it's not even about faults. It's about 
> >    missing pages.
> > 
> >    So call it something else. Maybe just "struct nopage". Or, "struct 
> >    vm_fault" at least, so that it's at least not about *random* faults.
> > 
> >  - drop "address" from "struct fault_data". Even if some user were to have 
> >    some reason to use it (doubtful), it should be called somethign long 
> >    and cumbersome, so that you don't use it by mistake, not realizing that 
> >    you should use the page index instead.
> 
> I'd rather have it in, even if it's long and cumbersome :-) As I said,
> there are a few HW drivers around the tree like spufs or some weirdo IBM
> infiniband stuff that do really tricky games with nopage/nopfn and which
> can have good use of it (at the very least, it's useful for debugging to
> printk where the accesses that ended up doing the wrong thing precisely
> was done :-)
> 
> >  - and keep calling it "nopage". 
> 
> Fine by me.

I won't do this. I'll keep calling it fault, because a) it means we keep
the backwards compatible ->nopage path until all drivers are converted,
and b) the page_mkwrite conversion really will make "nopage" the wrong
name.

I don't mind about the struct naming, but struct fault or struct nopage
seems weird to me... but whatever. Maybe we can change it to struct
fault_struct to go along with struct task_struct and struct mm_struct? ;)

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