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Subject: Re: [PATCH 2/2] nbd: add support for nbd as root device
To:     roman.stratiienko@globallogic.com, linux-kernel@vger.kernel.org,
        josef@toxicpanda.com, nbd@other.debian.org,
        A.Bulyshchenko@globallogic.com, linux-block@vger.kernel.org,
        axboe@kernel.dkn.org, "Richard W.M. Jones" <rjones@redhat.com>
References: <20190612163144.18486-1-roman.stratiienko@globallogic.com>
 <20190612163144.18486-2-roman.stratiienko@globallogic.com>
From:   Eric Blake <eblake@redhat.com>
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Organization: Red Hat, Inc.
Message-ID: <b988f702-f394-6f2e-43ea-61298c0f2b03@redhat.com>
Date:   Thu, 13 Jun 2019 08:02:56 -0500
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From: Eric Blake <eblake@redhat.com>
To: roman.stratiienko@globallogic.com, linux-kernel@vger.kernel.org,
 josef@toxicpanda.com, nbd@other.debian.org, A.Bulyshchenko@globallogic.com,
 linux-block@vger.kernel.org, axboe@kernel.dkn.org,
 "Richard W.M. Jones" <rjones@redhat.com>
Message-ID: <b988f702-f394-6f2e-43ea-61298c0f2b03@redhat.com>
Subject: Re: [PATCH 2/2] nbd: add support for nbd as root device
References: <20190612163144.18486-1-roman.stratiienko@globallogic.com>
 <20190612163144.18486-2-roman.stratiienko@globallogic.com>
In-Reply-To: <20190612163144.18486-2-roman.stratiienko@globallogic.com>

--GcPkFI5vKHhM5L3R0laXCr11kPXSMamS8
Content-Type: text/plain; charset=utf-8
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On 6/12/19 11:31 AM, roman.stratiienko@globallogic.com wrote:
> From: Roman Stratiienko <roman.stratiienko@globallogic.com>
>=20
> Adding support to nbd to use it as a root device. This code essentially=

> provides a minimal nbd-client implementation within the kernel. It open=
s
> a socket and makes the negotiation with the server. Afterwards it passe=
s
> the socket to the normal nbd-code to handle the connection.
>=20
> The arguments for the server are passed via kernel command line.
> The kernel command line has the format
> 'nbdroot=3D[<SERVER_IP>:]<SERVER_PORT>/<EXPORT_NAME>'.

Did you intend for nbdroot=3D1234 to connect to port 1234 or to server
1234 port 10809?  Is an export name mandatory even when it is the empty
string, in which case, is the / character mandatory?  Maybe this would
be better written as:

 [<SERVER_IP>[:<SERVER_PORT]][/<EXPORT_NAME]

although that would allow nbdroot=3D using all defaults (will that still
do the right thing?).

Should we support nbdroot=3DURI, and tie this in to Rich's proposal [1] o=
n
standardizing the set of URIs that refer to an NBD export?  It seems
like you are still limited to a TCP socket (not Unix) with no
encryption, so this would be equivalent to the URI:

nbd://[server[:port]][/export]

[1] https://lists.debian.org/nbd/2019/06/msg00011.html

--=20
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org


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