Stefan Hajnoczi <stefa...@redhat.com> writes:
> The raw_get_aio_fd() function allows virtio-blk-data-plane to get the
> file descriptor of a raw image file with Linux AIO enabled. This
> interface is really a layering violation that can be resolved once the
> block layer is able to run outside the global mutex - at that point
> virtio-blk-data-plane will switch from custom Linux AIO code to using
> the block layer.
>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
I think this creates user confusion because virtio-blk-data-plane can't
actually take a BDS.
So why not just make a string 'filename' property and open it directly
in virtio-blk-data-plane? Then it's at least clear to the user and
management tools what the device is capable of doing.
Regards,
Anthony Liguori
> ---
> block.h | 9 +++++++++
> block/raw-posix.c | 34 ++++++++++++++++++++++++++++++++++
> 2 files changed, 43 insertions(+)
>
> diff --git a/block.h b/block.h
> index 722c620..2dc6aaf 100644
> --- a/block.h
> +++ b/block.h
> @@ -365,6 +365,15 @@ void bdrv_disable_copy_on_read(BlockDriverState *bs);
> void bdrv_set_in_use(BlockDriverState *bs, int in_use);
> int bdrv_in_use(BlockDriverState *bs);
>
> +#ifdef CONFIG_LINUX_AIO
> +int raw_get_aio_fd(BlockDriverState *bs);
> +#else
> +static inline int raw_get_aio_fd(BlockDriverState *bs)
> +{
> + return -ENOTSUP;
> +}
> +#endif
> +
> enum BlockAcctType {
> BDRV_ACCT_READ,
> BDRV_ACCT_WRITE,
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index f2f0404..fc04981 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -1768,6 +1768,40 @@ static BlockDriver bdrv_host_cdrom = {
> };
> #endif /* __FreeBSD__ */
>
> +#ifdef CONFIG_LINUX_AIO
> +/**
> + * Return the file descriptor for Linux AIO
> + *
> + * This function is a layering violation and should be removed when it
> becomes
> + * possible to call the block layer outside the global mutex. It allows the
> + * caller to hijack the file descriptor so I/O can be performed outside the
> + * block layer.
> + */
> +int raw_get_aio_fd(BlockDriverState *bs)
> +{
> + BDRVRawState *s;
> +
> + if (!bs->drv) {
> + return -ENOMEDIUM;
> + }
> +
> + if (bs->drv == bdrv_find_format("raw")) {
> + bs = bs->file;
> + }
> +
> + /* raw-posix has several protocols so just check for raw_aio_readv */
> + if (bs->drv->bdrv_aio_readv != raw_aio_readv) {
> + return -ENOTSUP;
> + }
> +
> + s = bs->opaque;
> + if (!s->use_aio) {
> + return -ENOTSUP;
> + }
> + return s->fd;
> +}
> +#endif /* CONFIG_LINUX_AIO */
> +
> static void bdrv_file_init(void)
> {
> /*
> --
> 1.8.0
