Re: [Qemu-devel] [PATCH v4 1/1] block: pass the right options for BlockDriver.bdrv_open()

[Max Reitz <mreitz@redhat.com>]

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On 05.04.2017 11:19, Dong Jia Shi wrote:
> raw_open() expects the caller always passing in the right actual
> @options parameter. But when trying to applying snapshot on a RBD
> image, bdrv_snapshot_goto() calls raw_open() (by calling the
> bdrv_open callback on the BlockDriver) with a NULL @options, and
> that will result in a Segmentation fault.
> 
> For the other non-raw format drivers, it also makes sense to passing
> in the actual options, althought they don't trigger the problem so
> far.
> 
> Let's prepare a @options by adding the "file" key-value pair to a
> copy of the actual options that were given for the node (i.e.
> bs->options), and pass it to the callback.
> 
> BlockDriver.bdrv_open() expects bs->file to be NULL and just
> overwrites it with the result from bdrv_open_child(). That means we
> should actually make sure it's NULL because otherwise the child BDS
> will have a reference count that is 1 too high. So we unconditionally
> invoke bdrv_unref_child() before calling BlockDriver.bdrv_open(), and
> we wrap everything in bdrv_ref()/bdrv_unref() so the BDS isn't
> deleted in the meantime.
> 
> Suggested-by: Max Reitz <mreitz@redhat.com>
> Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> ---
>  block/snapshot.c | 26 +++++++++++++++++++++++---
>  1 file changed, 23 insertions(+), 3 deletions(-)

Thank you, I've applied the patch to my block branch (for inclusion in 2.9):

https://github.com/XanClic/qemu/commits/block

Max


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