Re: zap_page_range(): TLB flush race

[Manfred Spraul <manfreds@colorfullife.com>]

Alan Cox wrote:
> 
> 
> Basically establish_pte() has to be architecture specific, as some processors
> need different orders either to avoid races or to handle cpu specific
> limitations.
> 
I don't know: IMHO we have far to many architecture specific functions
in that area:

set_pte()
establish_pte()

flush_tlb()
update_mmu_cache();
flush_cache();
flush_icache();

Can't we merge them? 

<< 1)
set_pte(vma,pte,new_val);
	* flushes the cache, changes one pte, updates the tlb.
<< 2)
set_pte_new(vma,pte,new_val);
	* sets the pte, the old value was non-present. Most cpu
	  don't need to flush the tlb. (2.3.99 never flushes the tlb)
<< 3)
prepare_ptechange_{range,mm}(vma,start,end);
for()
	__set_pte(vma,pte,new_val);
commit_ptechange_{range,mm}(vma,start,end);
	*  should be used if you change multiple pages.
<<<<<<<<<
	
I don't understand the purpose of flush_page_to_ram():
filemap_sync_pte() calls it if MS_INVALIDATE is not set, it's not called
if MS_INVALIDATE is set.
In both cases, the kernel pointer is accessed in filemap_write_page().

--
	Manfred

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