Re: [PATCH] block: use the request length for iov alignment

[Keith Busch]

On Thu, Sep 08, 2022 at 09:45:26AM -0700, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> An iov length needs to be aligned to the logical block size, which may
> be larger than the memory alignment.

[cc'ing some other interested folks]

Any thoughts on this patch? It is fixing an observed IO error  when running
virtio-blk with the default 512b logical block size backed by a drive formatted
with 4k logical block.

> ---
>  block/io.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/io.c b/block/io.c
> index 0a8cbefe86..296d4b49a7 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -3243,13 +3243,14 @@ bool bdrv_qiov_is_aligned(BlockDriverState *bs, 
> QEMUIOVector *qiov)
>  {
>      int i;
>      size_t alignment = bdrv_min_mem_align(bs);
> +    size_t len = bs->bl.request_alignment;
>      IO_CODE();
>  
>      for (i = 0; i < qiov->niov; i++) {
>          if ((uintptr_t) qiov->iov[i].iov_base % alignment) {
>              return false;
>          }
> -        if (qiov->iov[i].iov_len % alignment) {
> +        if (qiov->iov[i].iov_len % len) {
>              return false;
>          }
>      }
> -- 
> 2.30.2
>