Re: [Qemu-devel] [PATCH] Add qerror message if the 'change' target filename can't be opened

[Kevin Wolf <kwolf@redhat.com>]

Am 01.04.2010 20:22, schrieb Luiz Capitulino:
> On Thu, 1 Apr 2010 15:15:51 -0300
> Luiz Capitulino <lcapitulino@redhat.com> wrote:
> 
>> On Thu, 25 Mar 2010 09:32:58 -0500
>> Ryan Harper <ryanh@us.ibm.com> wrote:
>>
>>> Currently when using the change command to switch the file in the cd drive
>>> the command doesn't complain if the file doesn't exit or can't be opened
>>> and the drive keeps the existing image.  This patch adds a qerror_report
>>> call to print a message out indicating the failure.  This error message
>>> can be used to catch failures.
>>
>>  Looks good to me, but it doesn't keep the existing image, it will silently
>> eject it instead.
> 
>  And, thinking more about it this seems the wrong behavior to me, if it
> fails to open the file, it should not touch the current one.
> 
>  Am I right, Kevin?

Well, it's a monitor command. I guess its meaning has never been clearly
defined, so I tend to say there is no right or wrong. From a user
perspective, intuitively I would expect that it succeeds completely or
maintains the old state, so yes.

However, I don't think it's fixable that easy. You obviously need to
close the image before you can open it. And reopening the image in case
of failure - well, we just had this discussion and I'm sure Juan wants
to comment on it...

It's a case that we should consider if/when we reorganize bdrv_open. The
"bdrv_close, but without closing the fd" thing doesn't work out here
because we need to reuse the same bs. Or maybe open a different bs first
and then copy things over. Could actually work this way.

Kevin