linux-kernel - Re: [RFC PATCH 0/6] Add support for shared PTEs across processes

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Message-Id: <20220121010806.5607-1-21cnbao@gmail.com>
Date:   Fri, 21 Jan 2022 09:08:06 +0800
From:   Barry Song <21cnbao@...il.com>
To:     khalid.aziz@...cle.com
Cc:     akpm@...ux-foundation.org, arnd@...db.de,
        dave.hansen@...ux.intel.com, david@...hat.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        longpeng2@...wei.com, rppt@...nel.org, surenb@...gle.com,
        willy@...radead.org
Subject: Re: [RFC PATCH 0/6] Add support for shared PTEs across processes

> A file under /sys/fs/mshare can be opened and read from. A read from
> this file returns two long values - (1) starting address, and (2)
> size of the mshare'd region.
> 
> --
> int mshare_unlink(char *name)
> 
> A shared address range created by mshare() can be destroyed using
> mshare_unlink() which removes the  shared named object. Once all
> processes have unmapped the shared object, the shared address range
> references are de-allocated and destroyed.

> mshare_unlink() returns 0 on success or -1 on error.

I am still struggling with the user scenarios of these new APIs. This patch
supposes multiple processes will have same virtual address for the shared
area? How can this be guaranteed while different processes can map different
stack, heap, libraries, files?

BTW, it seems you have different intention with the below?
Shared page tables during fork[1]
[1] https://lwn.net/Articles/861547/

Thanks
Barry