Re: [PATCH v2 0/7] mm: process_vm_mmap() -- syscall for duplication a process mapping

From: Kirill Tkhai
Date: Mon Jun 03 2019 - 10:43:03 EST

On 22.05.2019 18:22, Kirill A. Shutemov wrote:
> On Mon, May 20, 2019 at 05:00:01PM +0300, Kirill Tkhai wrote:
>> This patchset adds a new syscall, which makes possible
>> to clone a VMA from a process to current process.
>> The syscall supplements the functionality provided
>> by process_vm_writev() and process_vm_readv() syscalls,
>> and it may be useful in many situation.
> Kirill, could you explain how the change affects rmap and how it is safe.
> My concern is that the patchset allows to map the same page multiple times
> within one process or even map page allocated by child to the parrent.

Speaking honestly, we already support this model, since ZERO_PAGE() may
be mapped multiply times in any number of mappings.