[Libguestfs] nbdkit error: "write reply: NBD_CMD_WRITE: Broken pipe"

[Wouter Verhelst]

Same story.

On Fri, Jun 17, 2022 at 01:09:25PM +0200, Wouter Verhelst wrote:
> Hi, and sorry for the delay (I was overseas for a month in May to visit family
> etc)
> 
> On Tue, May 03, 2022 at 09:07:17AM +0100, Richard W.M. Jones wrote:
> > On Mon, May 02, 2022 at 03:36:33PM +0100, Nikolaus Rath wrote:
> > > So I tried to reproduce this, and noticed something odd. It seems I can
> > > disconnect the nbd device (nbd-client -d) while there are still requests
> > > in flight:
> > > 
> > > May 02 15:20:50 vostro.rath.org kernel: nbd1: detected capacity change from 0 to 52428800
> > > May 02 15:20:50 vostro.rath.org kernel: block nbd1: NBD_DISCONNECT
> > > May 02 15:20:50 vostro.rath.org kernel: block nbd1: Disconnected due to user request.
> > > May 02 15:20:50 vostro.rath.org kernel: block nbd1: shutting down sockets
> > > May 02 15:20:50 vostro.rath.org kernel: I/O error, dev nbd1, sector 776 op 0x0:(READ) flags 0x80700 phys_seg 29 prio class 0
> > > May 02 15:20:50 vostro.rath.org kernel: I/O error, dev nbd1, sector 776 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> > > May 02 15:20:50 vostro.rath.org kernel: Buffer I/O error on dev nbd1, logical block 97, async page read
> > > May 02 15:20:50 vostro.rath.org kernel: block nbd1: Attempted send on invalid socket
> > > May 02 15:20:50 vostro.rath.org kernel: I/O error, dev nbd1, sector 0 op 0x1:(WRITE) flags 0x800 phys_seg 0 prio class 0
> > > May 02 15:20:50 vostro.rath.org kernel: block nbd1: Attempted send on invalid socket
> > > May 02 15:20:50 vostro.rath.org kernel: I/O error, dev nbd1, sector 0 op 0x1:(WRITE) flags 0x800 phys_seg 0 prio class 0
> > > 
> > > This was generated by running:
> > > 
> > > $ nbd-client localhost /dev/nbd1 && mkfs.ext4 /dev/nbd1 && nbd-client -d
> > > /dev/nbd1
> > > 
> > > Is that expected behavior?
> > 
> > It's a bit unexpected to me.  Adding Wouter to the thread - he might
> > have an idea here, especially if there's a way to have "nbd-client -d"
> > wait for pending requests to finish before disconnecting.
> > 
> > I don't use the kernel client very much myself.  We mostly use either
> > libnbd or the qemu client.
> 
> The kernel is supposed to deal with this. If there are still processes
> using the device and/or, nbd-client -d should receive an error (I believe it
> was EPERM). If there are outstanding writes, the disconnect should flush
> those, wait for them to return, and *then* handle the disconnect.
> 
> At least those are the assumptions made in nbd-client ;-)
> 
> (I notice you did send this to the kernel maintainer too, but just
> wanted to follow up on what nbd-client assumes)
> 
> -- 
>      w at uter.{be,co.za}
> wouter@{grep.be,fosdem.org,debian.org}

-- 
     w at uter.{be,co.za}
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