Re: [patch 3/3] mm: fault handler to replace nopage and populate

[Benjamin Herrenschmidt]

> Wouldn't that confuse concurrent readers?
> 
> Could it be an option to make it safe for the fault handler to 
> temporarily drop the mmap_sem read lock given that some conditions TBD 
> are met?
> In that case it can retake the mmap_sem write lock, do the VMA flags 
> modifications, downgrade and do the pte modifications using a helper, or 
> even use remap_pfn_range() during the time the write lock is held?

If we return NOPAGE_REFAULT, then yes, we can drop the mmap sem, though
I 'm not sure we need that...

Ben.


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