Re: [Qemu-devel] [Qemu-block] [PATCH v3] block/rbd: increase dynamically the image size

[Stefano Garzarella <sgarzare@redhat.com>]

Kindly ping.

Thanks,
Stefano

On Thu, May 09, 2019 at 04:59:27PM +0200, Stefano Garzarella wrote:
> RBD APIs don't allow us to write more than the size set with
> rbd_create() or rbd_resize().
> In order to support growing images (eg. qcow2), we resize the
> image before write operations that exceed the current size.
> 
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
> v3:
>   - add 'image_size' field in the BDRVRBDState to keep track of the
>     current size of the RBD image [Jason, Kevin]
> ---
>  block/rbd.c | 42 +++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 39 insertions(+), 3 deletions(-)
> 
> diff --git a/block/rbd.c b/block/rbd.c
> index 0c549c9935..b0355a2ce0 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -102,6 +102,7 @@ typedef struct BDRVRBDState {
>      rbd_image_t image;
>      char *image_name;
>      char *snap;
> +    uint64_t image_size;
>  } BDRVRBDState;
>  
>  static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
> @@ -777,6 +778,14 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
>          goto failed_open;
>      }
>  
> +    r = rbd_get_size(s->image, &s->image_size);
> +    if (r < 0) {
> +        error_setg_errno(errp, -r, "error getting image size from %s",
> +                         s->image_name);
> +        rbd_close(s->image);
> +        goto failed_open;
> +    }
> +
>      /* If we are using an rbd snapshot, we must be r/o, otherwise
>       * leave as-is */
>      if (s->snap != NULL) {
> @@ -833,6 +842,22 @@ static void qemu_rbd_close(BlockDriverState *bs)
>      rados_shutdown(s->cluster);
>  }
>  
> +/* Resize the RBD image and update the 'image_size' with the current size */
> +static int qemu_rbd_resize(BlockDriverState *bs, uint64_t size)
> +{
> +    BDRVRBDState *s = bs->opaque;
> +    int r;
> +
> +    r = rbd_resize(s->image, size);
> +    if (r < 0) {
> +        return r;
> +    }
> +
> +    s->image_size = size;
> +
> +    return 0;
> +}
> +
>  static const AIOCBInfo rbd_aiocb_info = {
>      .aiocb_size = sizeof(RBDAIOCB),
>  };
> @@ -934,13 +959,25 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
>      }
>  
>      switch (cmd) {
> -    case RBD_AIO_WRITE:
> +    case RBD_AIO_WRITE: {
> +        /*
> +         * 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 (off + size > s->image_size) {
> +            r = qemu_rbd_resize(bs, off + size);
> +            if (r < 0) {
> +                goto failed_completion;
> +            }
> +        }
>  #ifdef LIBRBD_SUPPORTS_IOVEC
>              r = rbd_aio_writev(s->image, qiov->iov, qiov->niov, off, c);
>  #else
>              r = rbd_aio_write(s->image, off, size, rcb->buf, c);
>  #endif
>          break;
> +    }
>      case RBD_AIO_READ:
>  #ifdef LIBRBD_SUPPORTS_IOVEC
>              r = rbd_aio_readv(s->image, qiov->iov, qiov->niov, off, c);
> @@ -1051,7 +1088,6 @@ static int coroutine_fn qemu_rbd_co_truncate(BlockDriverState *bs,
>                                               PreallocMode prealloc,
>                                               Error **errp)
>  {
> -    BDRVRBDState *s = bs->opaque;
>      int r;
>  
>      if (prealloc != PREALLOC_MODE_OFF) {
> @@ -1060,7 +1096,7 @@ static int coroutine_fn qemu_rbd_co_truncate(BlockDriverState *bs,
>          return -ENOTSUP;
>      }
>  
> -    r = rbd_resize(s->image, offset);
> +    r = qemu_rbd_resize(bs, offset);
>      if (r < 0) {
>          error_setg_errno(errp, -r, "Failed to resize file");
>          return r;
> -- 
> 2.20.1
> 
> 

-- 

Stefano Garzarella
Software Engineer @ Red Hat