Message-Id: <5.1.0.14.2.20020324183746.0452cec0@pop.cus.cam.ac.uk>
Date: Sun, 24 Mar 2002 18:46:11 +0000
To: linux-kernel@vger.kernel.org
From: Anton Altaparmakov <aia21@cam.ac.uk>
Subject: Re: NBD client/server broken?
Cc: pavel@suse.cz, linux-fsdevel@vger.kernel.org
In-Reply-To: <5.1.0.14.2.20020324125307.02899da0@pop.cus.cam.ac.uk>
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Sender: linux-kernel-owner@vger.kernel.org

Just to keep interested parties informed:

Thanks to Steven Whitehouse I found out that the latest nbd client/server 
user space programs are in CVS on Sourceforge (the kernel nbd documentation 
needs updating to point to http://sf.net/projects/nbd)...

And I have just submitted a patch to Steven to make the nbd-server 64-bit 
clean on 32-bit machines and to allow proper auto detection of device size. 
Hopefully we will see it entering the CVS soon. Otherwise patch is 
available on request from me. (-:

Mounting a NTFS 15GiB partition over nbd (using ntfs tng driver) gave me a 
data throughput of 7-10MiB/sec over 100MBit ethernet (going via switch and 
a hub) which is quite impressive. (-:

Best regards,

Anton

At 13:10 24/03/02, Anton Altaparmakov wrote:
>Hi,
>
>I have been trying to get nbd to work, the server is 2.4.18-pre7-ac2 and 
>the client is 2.5.7, and the exported device is /dev/hda1 a 15GiB partition.
>
>I found and downloaded nbd.14.tar.gz. Is this the latest and greatest?
>
>Compiling the package gives several warnings and indeed the nbd-server 
>doesn't work. The size auto detection code is completely bogus because it 
>submits 64 bit variables via their address to system calls which only take 
>32 bit variables so you see silly things like
>
>es = (u64)-1
>
>turning into
>
>es = 0xffffffff01d4b139
>
>instead of
>
>es = 0x000000000whatever
>
>You either need to use 64 bit variants of the calls or you need to submit 
>a 32bit variable to the call, e.g. es32, and then expand it via es = (u64)es32.
>
>So I got past this and fixed size detection for myself.
>
>Now I get it to serve the first request but then it dies.
>
>On the server I see:
>
>[aia21@storm:~/nbd]$ ./nbd-server 5555 /dev/hda1 -r
>Entering request loop!
>1: *READ from 0 (0) len 4096, exp->buf, buf->net, +OK!
>2: *[aia21@storm:~/nbd]$
>
>And on the client I see:
>
>[aia21@drop nbd]$ dd if=/dev/nd1 of=ffff bs=1024 count=8
>NBD: receive - sock=-301251788 at buf=-65871580, size=16 returned 0.
>NBD: Recv control failed.(result 0)
>req should never be null
>Kernel call returned.Closing: que, sock, done
>NBD, minor 0: Request when not-ready.
>dd: reading `/dev/nd0': Input/output error
>4+0 records in
>4+0 records out
>[aia21@drop nbd]$
>
>The contents of the 4kiB of data transmitted are correct so we are 
>definitely on the right track but something seems to be aborting the 
>request loop in the server program.
>
>I will be looking into this as I _need_ this functionality very urgently 
>but I thought I would ask in case I have an out of data package of the nbd 
>utilities or someone has already fixed this and would like to share their 
>code with me...
>
>Best regards,
>
>Anton
>
>
>--
>   "I've not lost my mind. It's backed up on tape somewhere." - Unknown
>--
>Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
>Linux NTFS Maintainer / WWW: http://linux-ntfs.sf.net/
>ICQ: 8561279 / WWW: http://www-stu.christs.cam.ac.uk/~aia21/
>
>-
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-- 
   "I've not lost my mind. It's backed up on tape somewhere." - Unknown
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Linux NTFS Maintainer / WWW: http://linux-ntfs.sf.net/
ICQ: 8561279 / WWW: http://www-stu.christs.cam.ac.uk/~aia21/

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