Re: [PATCH V2 for-6.2 2/2] block/rbd: workaround for ceph issue #53784

[Ilya Dryomov]

On Thu, Jan 13, 2022 at 3:44 PM Peter Lieven <pl@kamp.de> wrote:
>
> librbd had a bug until early 2022 that affected all versions of ceph that
> supported fast-diff. This bug results in reporting of incorrect offsets
> if the offset parameter to rbd_diff_iterate2 is not object aligned.
>
> This patch works around this bug for pre Quincy versions of librbd.
>
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>  block/rbd.c | 42 ++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 40 insertions(+), 2 deletions(-)
>
> diff --git a/block/rbd.c b/block/rbd.c
> index 20bb896c4a..d174d51659 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -1320,6 +1320,7 @@ static int coroutine_fn 
> qemu_rbd_co_block_status(BlockDriverState *bs,
>      int status, r;
>      RBDDiffIterateReq req = { .offs = offset };
>      uint64_t features, flags;
> +    uint64_t head = 0;
>
>      assert(offset + bytes <= s->image_size);
>
> @@ -1347,7 +1348,43 @@ static int coroutine_fn 
> qemu_rbd_co_block_status(BlockDriverState *bs,
>          return status;
>      }
>
> -    r = rbd_diff_iterate2(s->image, NULL, offset, bytes, true, true,
> +#if LIBRBD_VERSION_CODE < LIBRBD_VERSION(1, 17, 0)
> +    /*
> +     * librbd had a bug until early 2022 that affected all versions of ceph 
> that
> +     * supported fast-diff. This bug results in reporting of incorrect 
> offsets
> +     * if the offset parameter to rbd_diff_iterate2 is not object aligned.
> +     * Work around this bug by rounding down the offset to object boundaries.
> +     * This is OK because we call rbd_diff_iterate2 with whole_object = true.
> +     * However, this workaround only works for non cloned images with default
> +     * striping.
> +     *
> +     * See: https://tracker.ceph.com/issues/53784
> +     */
> +
> +    /*  check if RBD image has non-default striping enabled */

Nit: extra space

Thanks,

                Ilya