Re: [PATCH] blkio: Respect memory-alignment for bounce buffer allocations

[Stefano Garzarella]

On Wed, Jan 31, 2024 at 06:31:40PM +0100, Kevin Wolf wrote:
> blkio_alloc_mem_region() requires that the requested buffer size is a
> multiple of the memory-alignment property. If it isn't, the allocation
> fails with a return value of -EINVAL.
>
> Fix the call in blkio_resize_bounce_pool() to make sure the requested
> size is properly aligned.
>
> I observed this problem with vhost-vdpa, which requires page aligned
> memory. As the virtio-blk device behind it still had 512 byte blocks, we
> got bs->bl.request_alignment = 512, but actually any request that needed
> a bounce buffer and was not aligned to 4k would fail without this fix.
>
> Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
> block/blkio.c | 3 +++
> 1 file changed, 3 insertions(+)

Thanks for fixinig this!

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

> diff --git a/block/blkio.c b/block/blkio.c
> index 0a0a6c0f5f..b989617608 100644
> --- a/block/blkio.c
> +++ b/block/blkio.c
> @@ -89,6 +89,9 @@ static int blkio_resize_bounce_pool(BDRVBlkioState *s, 
> int64_t bytes)
>     /* Pad size to reduce frequency of resize calls */
>     bytes += 128 * 1024;
>
> +    /* Align the pool size to avoid blkio_alloc_mem_region() failure */
> +    bytes = QEMU_ALIGN_UP(bytes, s->mem_region_alignment);
> +
>     WITH_QEMU_LOCK_GUARD(&s->blkio_lock) {
>         int ret;
>
> --
> 2.43.0