Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux2.6.34-rc3)

[Linus Torvalds]

On Wed, 7 Apr 2010, Minchan Kim wrote:
> 
> unmap_and_move
> 	remove_migration_ptes
> 		rmap_walk
> 			rmap_walk_anon
> 
> We always has rcu_read_lock about anon page in unmap_and_move.
> So I think it's not buggy. What am I missing?

Ok, in that case it's fine.

However, it does bring back my comment about all those anonvma changes: 
the locking is totally undocumented. 

Why isn't there a thing _saying_ that it's ok because of this?

Why is there no comment about the locking of that 'same_vma' / 
'vma->anon_vma_chain' except for the totally nonsensical one about 
page_table_lock (which doesn't protect _any_ of the other cases)?

		Linus
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