Re: [Qemu-devel] [PATCH] Disable O_DIRECT for physical CDROM/DVD drives

[Kevin Wolf <kwolf@redhat.com>]

Am 20.07.2010 17:17, schrieb Jes.Sorensen@redhat.com:
> From: Jes Sorensen <Jes.Sorensen@redhat.com>
> 
> O_DIRECT (cache=none) requires sector alignment, however the physical
> sector size of CDROM/DVD drives is 2048, as opposed to most disk
> devices which use 512. QEMU is hard coding 512 all over the place, so
> allowing O_DIRECT for CDROM/DVD devices does not work.
> 
> Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
> ---
>  block/raw-posix.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 291699f..0ea79b6 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -1139,6 +1139,11 @@ static int cdrom_open(BlockDriverState *bs, const char *filename, int flags)
>      BDRVRawState *s = bs->opaque;
>  
>      s->type = FTYPE_CD;
> +    if (flags & BDRV_O_NOCACHE) {
> +        fprintf(stderr, "Disabling unsupported O_DIRECT (cache=none) for "
> +                "CDROM/DVD device (%s)\n", filename);
> +        flags &= ~BDRV_O_NOCACHE;
> +    }

Good point. Just one detail: We should probably change bs->open_flags,
too, to keep things consistent.

Kevin