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

[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;
+    }
 
     /* open will not fail even if no CD is inserted, so add O_NONBLOCK */
     return raw_open_common(bs, filename, flags, O_NONBLOCK);
-- 
1.7.1.1