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Re: [Qemu-devel] [PATCH] Error on O_DIRECT for physical CDROM/DVD drives
From: |
David S. Ahern |
Subject: |
Re: [Qemu-devel] [PATCH] Error on O_DIRECT for physical CDROM/DVD drives |
Date: |
Tue, 20 Jul 2010 10:35:10 -0600 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100621 Fedora/3.0.5-1.fc13 Lightning/1.0b2pre Thunderbird/3.0.5 |
On 07/20/10 10:09, address@hidden wrote:
> From: Jes Sorensen <address@hidden>
>
> 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. Exit with an
> error!
>
> Signed-off-by: Jes Sorensen <address@hidden>
> ---
> 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..1b840c4 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, "O_DIRECT (cache=none) for CDROM/DVD device (%s) "
> + "is unsupported\n", filename);
> + exit(1);
> + }
If a cdrom is added via the monitor this would abruptly terminate the VM
- which is not good.
David
>
> /* open will not fail even if no CD is inserted, so add O_NONBLOCK */
> return raw_open_common(bs, filename, flags, O_NONBLOCK);