Re: [Qemu-devel] [PATCH v2] block: Close backing file early in bdrv_img_create

[Wenchao Xia]

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 <address@hidden>
> ---
> 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;
            }

  It is not a big problem, I am OK if you stick to this version.