To:     David Hildenbrand <david@redhat.com>,
        Christoph Hellwig <hch@lst.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc:     Hugh Dickins <hughd@google.com>,
        Seth Jennings <sjenning@redhat.com>,
        Dan Streetman <ddstreet@ieee.org>,
        Vitaly Wool <vitaly.wool@konsulko.com>,
        Matthew Wilcox <willy@infradead.org>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org
References: <20211224062246.1258487-1-hch@lst.de>
 <10ec73d4-6658-4f60-abe1-84ece53ca373@redhat.com>
From:   Juergen Gross <jgross@suse.com>
Subject: Re: remove Xen tmem leftovers
Message-ID: <82dbdc2c-20c2-d69b-bdc9-efc54939d54c@suse.com>
Date:   Wed, 5 Jan 2022 07:08:12 +0100
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From: Juergen Gross <jgross@suse.com>
To: David Hildenbrand <david@redhat.com>, Christoph Hellwig <hch@lst.de>,
 Andrew Morton <akpm@linux-foundation.org>,
 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Hugh Dickins <hughd@google.com>, Seth Jennings <sjenning@redhat.com>,
 Dan Streetman <ddstreet@ieee.org>, Vitaly Wool <vitaly.wool@konsulko.com>,
 Matthew Wilcox <willy@infradead.org>, linux-kernel@vger.kernel.org,
 linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Message-ID: <82dbdc2c-20c2-d69b-bdc9-efc54939d54c@suse.com>
Subject: Re: remove Xen tmem leftovers
References: <20211224062246.1258487-1-hch@lst.de>
 <10ec73d4-6658-4f60-abe1-84ece53ca373@redhat.com>
In-Reply-To: <10ec73d4-6658-4f60-abe1-84ece53ca373@redhat.com>

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On 04.01.22 15:31, David Hildenbrand wrote:
> On 24.12.21 07:22, Christoph Hellwig wrote:
>> Hi all,
>>
>> since the remove of the Xen tmem driver in 2019, the cleancache hooks =
are
>> entirely unused, as are large parts of frontswap.  This series against=

>> linux-next (with the folio changes included) removes cleancaches, and =
cuts
>> down frontswap to the bits actually used by zswap.
>>
>=20
> Just out of curiosity, why was tmem removed from Linux (or even Xen?).
> Do you have any information?

tmem never made it past the "experimental" state in the Xen hypervisor.
Its implementation had some significant security flaws, there was no
maintainer left, and nobody stepped up to address those issues.

As a result tmem was removed from Xen.


Juergen

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