Re: [PATCH 4/5] mm: soft-dirty bits for user memory changes tracking

[Pavel Emelyanov]

On 07/11/2013 10:46 PM, Andy Lutomirski wrote:
> 
> Sorry I'm late to the party -- I didn't notice this until the lwn
> article this week.
> 
> How does this get munmap + mmap right?  mremap marks things soft-dirty,
> but unmapping and remapping seems like it will result in the soft-dirty
> bit being cleared.  For that matter, won't this sequence also end up wrong:
> 
>  - clear_refs
>  - Write to mapping
>  - Page and pte evicted due to memory pressure
>  - Read from mapping -- clean page faulted back in
>  - pte soft-dirty is now clear ?!?

Yes, it looks like this problem exists. I'll look what can be done about
it, thank you.

> --Andy

Pavel
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