linux-kernel - Re: Sealed memfd & no-fault mmap

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Message-ID: <20210429183836.GF8339@xz-x1>
Date:   Thu, 29 Apr 2021 14:38:36 -0400
From:   Peter Xu <peterx@...hat.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Simon Ser <contact@...rsion.fr>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Will Deacon <will@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Herrmann <dh.herrmann@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Greg Kroah-Hartman <greg@...ah.com>,
        "tytso@....edu" <tytso@....edu>
Subject: Re: Sealed memfd & no-fault mmap

On Thu, Apr 29, 2021 at 06:48:07PM +0300, Kirill A. Shutemov wrote:
> > Side note: this will only ever work for non-shared mappings.
> 
> I think it's show-stopper for the use-case, no? IIUC, the mappings is used
> for communication between a compositor and a client and has to be shared.

Yes I had the same doubt..  Besides, we probably don't want to convert all
VM_FAULT_SIGBUS to fallback to anonymous pages, as I see that vmf_error()
converts mostly everything besides -ENOMEM to VM_FAULT_SIGBUS.  Thanks,

-- 
Peter Xu