On Wed, Mar 2, 2011 at 3:04 PM, Ryan Harper <ry...@us.ibm.com> wrote:
> If the block device has been closed, we no longer have a medium to submit
> IO against, check for this before submitting io. This prevents a segfault
> further in the code where we dereference elements of the block driver.
>
> Signed-off-by: Ryan Harper <ry...@us.ibm.com>
> ---
> block.c | 5 +++++
> 1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/block.c b/block.c
> index 92dd3fe..534e1bc 100644
> --- a/block.c
> +++ b/block.c
> @@ -2407,6 +2407,11 @@ int bdrv_aio_multiwrite(BlockDriverState *bs,
> BlockRequest *reqs, int num_reqs)
> return 0;
> }
>
> + /* don't submit writes if we don't have a medium */
> + if (bs->drv == NULL) {
> + return -1;
> + }
> +
Most other bdrv_*() calls will error out immediately if !bs->drv.
Here you check only after returning success for num_reqs == 0. I
don't think it makes a huge difference and can see how these semantics
are handy (saves caller checking for num_reqs == 0), but I wanted to
point it out.
More importantly, we're not obeying the contract of this function
here. reqs[].error must be set to -ENOMEDIUM before returning -1.
Otherwise the caller thinks that reqs[] callbacks will still be
invoked in the future and cannot complete those requests.
Stefan
