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Re: [Qemu-devel] [PATCH] Disable O_DIRECT for physical CDROM/DVD drives
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH] Disable O_DIRECT for physical CDROM/DVD drives |
Date: |
Tue, 20 Jul 2010 17:40:00 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-2.fc12 Thunderbird/3.0.4 |
Am 20.07.2010 17:17, schrieb address@hidden:
> 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.
>
> 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..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
Re: [Qemu-devel] Re: [PATCH] Disable O_DIRECT for physical CDROM/DVD drives, Kevin Wolf, 2010/07/20