Re: [Qemu-devel] [PATCH RESEND 19/50] blockdev: Use BlockBackend for blockdev-backup TA

[Max Reitz]

On 2015-01-27 at 16:59, Eric Blake wrote:
> On 01/27/2015 12:45 PM, Max Reitz wrote:
> > When preparing a blockdev-backup transaction, the BlockBackend should be
> > used because there may be no medium associated to the BB (which would
> > make bdrv_find() fail, whereas blk_by_name() does not).
> >
> > This does not make a real difference because blockdev-backup will fail
> > without a medium anyway; however, it will have an impact on the error
> > returned ("device not found" vs. "no medium").
> >
> > Signed-off-by: Max Reitz <address@hidden>
> > ---
> >   blockdev.c | 17 ++++++++++-------
> >   1 file changed, 10 insertions(+), 7 deletions(-)
> And no tests changed output as a result?  Might be worth adding a test
> for the error message.

Actually, it's preventing a test output change: At this point, a BB 
always has a BDS, thus there is no change (if blk_by_name() works, 
bdrv_find() will work, too). This will change only later (patches 34 and 
40), at which point the message would change to "device not found" 
without this patch (and as far as I remember, qemu-iotest 055 tests the 
error type).

Max