Re: [patch][rfc] mm: have expand_stack honour VM_LOCKED

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

Hi Nick,

> Is this valid?
> 
> 
> It appears that direct callers of expand_stack may not properly lock the newly
> expanded stack if they don't call make_pages_present (page fault handlers do
> this).

When happend this issue?

I think...

case 1. explit mlock to stack 

   1. mlock to stack
        -> make_pages_present is called via mlock(2).
   2. stack increased
        -> no page fault happened.

case 2. swapout and mlock stack

   1. stack swap out
   2. mlock to stack
        -> the page doesn't swap in at the time.
   3. page fault in the stack
        -> the page swap in
           (no need make_present_page())


So, it seems this patch isn't necessary.




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