Re: Read/Write migration entries: Implement correct behavior in copy_one_pte

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Tue, 18 Apr 2006 18:27:28 -0700 (PDT)
Christoph Lameter <clameter@sgi.com> wrote:

> On Wed, 19 Apr 2006, KAMEZAWA Hiroyuki wrote:
> 
> > > Note that this is again only a partial solution. mprotect() also has the
> > > potential of changing the write status to read. 
> > yes. in change_pte_range(). 
> > 
> > Note:
> > fork() and mprotect() both requires mm->mmap_sem.
> > So both of them is not problem when migration holds mm->mmap_sem.
> > If we does lazy migration or memory hot removing or allows migration from
> > another process, this will be problem.
> 
> Oh. We already allow migration from another process since the page may 
> be mapped by multiple mm's. Page migration will then replace the ptes in 
> *all* mm_structs that map this page with migration entries.
> 
> So we need a fix here.
> 
Ah.....yes. sorry.

In my understanding (and grep), read/write protection for anon pages 
can be changed under

- fork()
- mprotect()

all are known.

BTW, do we manage page table under move_vma() in right way ?

-Kame

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