On Mon, Dec 02, 2013 at 11:37:36AM +0800, Wenchao Xia wrote:
> 于 2013/11/30 4:41, Max Reitz 写道:
> > Leaving the backing file open although it is not needed anymore can
> > cause problems if it is opened through a block driver which allows
> > exclusive access only and if the create function of the block driver
> > used for the top image (the one being created) tries to close and reopen
> > the image file (which will include opening the backing file a second
> > time).
> >
> > In particular, this will happen with a backing file opened through
> > qemu-nbd and using qcow2 as the top image file format (which reopens the
> > image to flush it to disk).
> >
> > Signed-off-by: Max Reitz <mre...@redhat.com>
> > ---
> > v2:
> > - Minimizing the changes prevents introducing a leak of the
> > BlockDriverState in case of an error in bdrv_open() (thanks, Kevin).
> > ---
> > block.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
>
> Minor comments:
> I think your v1 have better orgnize of code, since it tips reader
> that bs is a variable used only in backing file code. Why not improve
> it by just adding one line in v1:
>
> line 4587:
> ret = bdrv_open(bs, backing_file->value.s, NULL, back_flags,
> backing_drv, &local_err);
> if (ret < 0) {
> error_setg_errno(errp, -ret, "Could not open '%s': %s",
> backing_file->value.s,
> error_get_pretty(local_err));
> error_free(local_err);
> local_err = NULL;
> bdrv_unref(bs);
> goto out;
> }
Agreed, tightening the scope of 'bs' was a good idea.
Max: can you send a final version as suggested by Wenchao?
Thanks,
Stefan
