Re: [Qemu-devel] [Qemu-block] [PATCH] Report error when opening device with locked tray

[John Snow <jsnow@redhat.com>]

On 06/07/2016 06:28 AM, Kevin Wolf wrote:
> Am 06.06.2016 um 21:40 hat Colin Lord geschrieben:
>> This commit causes qmp_blockdev_change_medium to report an error if an
>> attempt is made to open a device with a locked tray.
> 
> The old behaviour is that the command seemingly succeeds, but the medium
> isn't actually changed. Correct?
> 

Close. Old "change" command also fails, but with a confusing error.

> Should this be mentioned in the commit message? You just describe what
> you change, but not why.
> 

Old behavior:

- Change uses qmp_blockdev_open_tray, which "succeeds."
- Change then tries to use qmp_x_blockdev_remove_medium, but receives
potentially confusing error "Tray is locked."
- Moments later, the tray is likely now open.

New behavior:

- Change uses do_open_tray, which returns -EINPROGRESS.
- Change can propagate this error upwards without attempting to remove
the medium.
- User gets "Device <foo> is locked and force was not specified, wait
for tray to open and try again" error.

Why: "The new error tries to inform the user that there is an action
pending and that the command, if run again, may succeed."

>> Signed-off-by: Colin Lord <clord@redhat.com>
>> This is based off my previous patch regarding the do_open_tray function
>> (currently at v3). Probably should have been submitted as a patch set
>> but I wasn't thinking that far ahead when I submitted the first patch.
>> ---
>>  blockdev.c | 7 +++++--
>>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> Yes, would probably have made sense as a series, but as long as it's
> only two patches, it's not really a problem.
> 
> Please make sure to put such comments below the "---" line, though, i.e.
> comments that make sense for the review, but not as part of the commit
> log. Then git-am automatically removes that part from the commit message
> while applying the patch. I did it manually for this one now.
> 
> Kevin
> 

-- 
—js