Re: [RFC 1/2] [RFC] mm: Account anon mappings as RLIMIT_DATA

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Mon, Dec 14, 2015 at 03:51:26PM +0100, Quentin Casasnovas wrote:
...
> 
> Do we want to fold may_expand_anon_vm() into may_expand_vm() (potentially
> passing it the flags/struct file if needed) so there is just one such
> helper function?  Rationale being that it then gets hard to see what
> restricts what, and it's easy to miss one place.

I tried to make the patch small as possible (because otherwise indeed
I would have to pass @vm_file|@file as additional argument). This won't
be a problem but may_expand_vm is called way more times than
may_expand_anon_vm. That's the only rationale I followed.

> For example, I couldn't find anything preventing a user to
> mmap(MAP_GROWSDOWN) and uses that as a base to get pages that would not be
> accounted for in your patch (making it a poor-man mremap()).

growsup/down stand for stack usage iirc, so it was intentionally
not accounted here.

> 
> I only had a quick look so apologies if this is handled and I missed it :)

thanks for feedback! also take a look on Kostya's patch, I think it's
even better approach (and I like it more than mine).

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