Re: [Qemu-devel] [PATCH v2 04/37] hw/usb-storage: Check whether BB is inserted

[Max Reitz <mreitz@redhat.com>]

On 2015-03-04 at 09:20, Kevin Wolf wrote:
> Am 04.03.2015 um 15:07 hat Max Reitz geschrieben:
>> On 2015-03-04 at 09:02, Kevin Wolf wrote:
>>> Am 09.02.2015 um 18:11 hat Max Reitz geschrieben:
>>>> Only call bdrv_key_required() on the BlockDriverState if the
>>>> BlockBackend has an inserted medium.
>>>>
>>>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>>>> Reviewed-by: Eric Blake <eblake@redhat.com>
>>>> ---
>>>>   hw/usb/dev-storage.c | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/hw/usb/dev-storage.c b/hw/usb/dev-storage.c
>>>> index 4539733..3123baf 100644
>>>> --- a/hw/usb/dev-storage.c
>>>> +++ b/hw/usb/dev-storage.c
>>>> @@ -638,7 +638,7 @@ static void usb_msd_realize_storage(USBDevice *dev, Error **errp)
>>>>       usb_msd_handle_reset(dev);
>>>>       s->scsi_dev = scsi_dev;
>>>> -    if (bdrv_key_required(blk_bs(blk))) {
>>>> +    if (blk_is_inserted(blk) && bdrv_key_required(blk_bs(blk))) {
>>>>           if (cur_mon) {
>>>>               monitor_read_bdrv_key_start(cur_mon, blk_bs(blk),
>>>>                                           usb_msd_password_cb, s);
>>> Why would bdrv_key_required() ever return true when no medium is
>>> inserted? Sounds like a bug to me, like not resetting state correctly on
>>> bdrv_close() of an encrypted image.
>> The point is that blk_bs(blk) might be NULL.
> This is not what blk_is_inserted() is checking. It happens to protect
> you against segfaults because it's robust against using NULL, but with
> an existing BDS, checking whether there is a medium inserted (in the
> physical device for passthrough drivers) doesn't make sense.

Not right now it's not. See patch 6.

Yes, I will include my patch order justification chapter from v1 in the 
cover letter of v3.

Max