Re: [PATCH] block/rbd: fix write zeroes with growing images

[Peter Lieven]

> Am 17.03.2022 um 17:26 schrieb Stefano Garzarella <sgarzare@redhat.com>:
> 
> Commit d24f80234b ("block/rbd: increase dynamically the image size")
> added a workaround to support growing images (eg. qcow2), resizing
> the image before write operations that exceed the current size.
> 
> We recently added support for write zeroes and without the
> workaround we can have problems with qcow2.
> 
> So let's move the resize into qemu_rbd_start_co() and do it when
> the command is RBD_AIO_WRITE or RBD_AIO_WRITE_ZEROES.
> 
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2020993
> Fixes: c56ac27d2a ("block/rbd: add write zeroes support")
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
> block/rbd.c | 26 ++++++++++++++------------
> 1 file changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/block/rbd.c b/block/rbd.c
> index 8f183eba2a..6caf35cbba 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -1107,6 +1107,20 @@ static int coroutine_fn 
> qemu_rbd_start_co(BlockDriverState *bs,
> 
>     assert(!qiov || qiov->size == bytes);
> 
> +    if (cmd == RBD_AIO_WRITE || cmd == RBD_AIO_WRITE_ZEROES) {
> +        /*
> +         * RBD APIs don't allow us to write more than actual size, so in 
> order
> +         * to support growing images, we resize the image before write
> +         * operations that exceed the current size.
> +         */
> +        if (offset + bytes > s->image_size) {
> +            int r = qemu_rbd_resize(bs, offset + bytes);
> +            if (r < 0) {
> +                return r;
> +            }
> +        }
> +    }
> +
>     r = rbd_aio_create_completion(&task,
>                                   (rbd_callback_t) qemu_rbd_completion_cb, 
> &c);
>     if (r < 0) {
> @@ -1182,18 +1196,6 @@ coroutine_fn qemu_rbd_co_pwritev(BlockDriverState *bs, 
> int64_t offset,
>                                  int64_t bytes, QEMUIOVector *qiov,
>                                  BdrvRequestFlags flags)
> {
> -    BDRVRBDState *s = bs->opaque;
> -    /*
> -     * RBD APIs don't allow us to write more than actual size, so in order
> -     * to support growing images, we resize the image before write
> -     * operations that exceed the current size.
> -     */
> -    if (offset + bytes > s->image_size) {
> -        int r = qemu_rbd_resize(bs, offset + bytes);
> -        if (r < 0) {
> -            return r;
> -        }
> -    }
>     return qemu_rbd_start_co(bs, offset, bytes, qiov, flags, RBD_AIO_WRITE);
> }
> 
> -- 
> 2.35.1
> 

Do we really have a use case for growing rbd images?

Peter