Re: [Qemu-devel] qcow2 problem: while a qcow2 image run out of disk space the guest paused

[tu bo <tubo@linux.vnet.ibm.com>]

Dears,

Xiao Guang Chen left IBM last week, and I changed owner from XiangGuang 
to me for this issue.

XiaoGuang told me this is by design, and probably I can close it if no 
news.  My understanding is that I can close it now. If I'm wrong, please 
correct me.  thanks a lot


From:    Kevin Wolf <kwolf@redhat.com>
To:    Alexandre DERUMIER <aderumier@odiso.com>
Cc:    chenxg <chenxg@linux.vnet.ibm.com>, stefanha 
<stefanha@redhat.com>, mimu@linux.vnet.ibm.com, Bo Tu/China/IBM@IBMCN, 
borntraeger@de.ibm.com, Holger Wolf <Holger.Wolf@de.ibm.com>, qemu-devel 
<qemu-devel@nongnu.org>
Date:    04/17/2015 03:57 PM
Subject:    Re: [Qemu-devel] qcow2 problem: while a qcow2 image run out 
of disk space the guest paused.


Am 17.04.2015 um 06:30 hat Alexandre DERUMIER geschrieben:
 > Hi,
 >
 > Isn't it related to drive options ?
 >
 >
 > "
 > werror=action,rerror=action
 >
 > Specify which action to take on write and read errors. Valid actions 
are: “ignore” (ignore the error and try to continue), “stop” (pause 
QEMU), “report” (report the error to the guest), “enospc” (pause QEMU 
only if the host disk is full; report the error to the guest 
otherwise).  The default setting is werror=enospc and rerror=report.
 > "

Yes, it is.

Generally you don't want to report such errors to the guest, because the
guest sees that the disk is broken and stops using it. Even if you free
some space, you wouldn't easily get the guest to use the disk again
without rebooting. But if you really want, you can configure it so.

It is not expected that the guest gets I/O errors (except possibly
network timeouts if the VM is stopped for too long) or even qemu
crashes. If it crashes again for you, please provide a gdb backtrace.

Kevin

 > ----- Mail original -----
 > De: "chenxg" <chenxg@linux.vnet.ibm.com>
 > À: "Kevin Wolf" <kwolf@redhat.com>, "stefanha" <stefanha@redhat.com>, 
mimu@linux.vnet.ibm.com, tubo@cn.ibm.com, borntraeger@de.ibm.com, 
"Holger Wolf" <Holger.Wolf@de.ibm.com>, "qemu-devel" <qemu-devel@nongnu.org>
 > Envoyé: Vendredi 17 Avril 2015 04:22:57
 > Objet: [Qemu-devel] qcow2 problem: while a qcow2 image run out of 
disk space the guest paused.
 >
 > Hi Kevin,
 >
 > While installing a guest into a qcow2 image if the qcow2 image run out
 > of disk space, the guest will stop work and change state to paused
 > without messages.
 >
 > When we tried to free up disk space in the host and the virsh resume to
 > work. The guest then got I/O errors but later on QEMU also crashed.
 >
 > A guest in paused state is certainly not the best result.
 >
 > Probably good way to react are:
 > - return I/O errors to the guest and the let the guest handle those
 > (Linux file system code might just crash)
 > - allow resume only when disk is free again.
 >
 > What's your opinion?
 >