Re: [Qemu-devel] [PATCH] rbd: print a clear error message when write beyond EOF

[Josh Durgin]

On 12/10/2014 07:47 AM, Jun Li wrote:
> Currently, as rbd driver do not support dynamic growth when write beyond EOF,
> so just print a clear error message.
>
> Signed-off-by: Jun Li <address@hidden>
> ---
>   block/rbd.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
>
> diff --git a/block/rbd.c b/block/rbd.c
> index 5b5a64a..65b01f0 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -693,6 +693,20 @@ static BlockAIOCB *qemu_rbd_aio_writev(BlockDriverState 
> *bs,
>                                          BlockCompletionFunc *cb,
>                                          void *opaque)
>   {
> +    BDRVRBDState *s = bs->opaque;
> +    uint64_t total_size;
> +    int64_t off, size;
> +
> +    off = sector_num * BDRV_SECTOR_SIZE;
> +    size = nb_sectors * BDRV_SECTOR_SIZE;
> +    rbd_get_size(s->image, &total_size);
> +
> +    if (off + size > total_size) {
> +        fprintf(stdout, "Image formats that grow on demand"
> +                        "are not supported on rbd.\n");
> +        return NULL;
> +    }
> +
>       return rbd_start_aio(bs, sector_num, qiov, nb_sectors, cb, opaque,
>                            RBD_AIO_WRITE);
>   }

This is one of the checks librbd does itself, so we could just look for
an EINVAL from rbd_aio_{read,write,discard} in rbd_start_aio()
to avoid duplicating the check. An out of bounds i/o is the only way
EINVAL can be returned from these functions in librbd.

Josh