Re: [Qemu-devel] [PATCH 1/4] Fix migration in case of scsi-generic

[Paolo Bonzini <pbonzini@redhat.com>]

On 08/05/2015 13:38, Dimitris Aragiorgis wrote:
> During migration, QEMU uses fsync()/fdatasync() on the open file
> descriptor for read-write block devices to flush data just before
> stopping the VM.
> 
> However, fsync() on a scsi-generic device returns -EINVAL which
> causes the migration to fail. This patch skips flushing data in case
> of an SG device, since submitting SCSI commands directly via an SG
> character device (e.g. /dev/sg0) bypasses the page cache completely,
> anyway.

Good catch!  The patch is correct, but please remove the same test from
iscsi_co_flush (in block/iscsi.c) because it's now duplicate.

Thanks,

Paolo

> Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
> ---
>  block/io.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/io.c b/block/io.c
> index 1ce62c4..d248a4d 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -2231,7 +2231,7 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
>  {
>      int ret;
>  
> -    if (!bs || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
> +    if (!bs || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs) || bdrv_is_sg(bs)) {
>          return 0;
>      }
>  
>