Re: [libvirt] [Qemu-devel] [PATCH v2 3/3] raw-posix: Re-open host CD-ROM after media change

Piggy-back on the guest CD-ROM polling to poll on the host.  Open and close the host CD-ROM file descriptor to ensure we read the new size and not a stale size. Two things are going on here: 1. If hald/udisks is not already polling CD-ROMs on the host then   re-opening the CD-ROM causes the host to read the new medium's size. 2. There is a bug in Linux which means the CD-ROM file descriptor must   be re-opened in order for lseek(2) to see the new size.  The   inode size gets out of sync with the underlying device (which you can   confirm by checking that /sys/block/sr0/size and lseek(2) do not   match after media change).  I have raised this with the   maintainers but we need a workaround for the foreseeable future. Note that these changes are all in a #ifdef __linux__ section. Signed-off-by: Stefan Hajnoczi <stefanha(a)linux.vnet.ibm.com&gt; ---  block/raw-posix.c |   26 ++++++++++++++++++++++----  1 files changed, 22 insertions(+), 4 deletions(-) diff --git a/block/raw-posix.c b/block/raw-posix.c index 6b72470..8b5205c 100644 --- a/block/raw-posix.c +++ b/block/raw-posix.c @@ -1238,10 +1238,28 @@ static int cdrom_is_inserted(BlockDriverState *bs)     BDRVRawState *s = bs->opaque;     int ret; -    ret = ioctl(s->fd, CDROM_DRIVE_STATUS, CDSL_CURRENT); -    if (ret == CDS_DISC_OK) -        return 1; -    return 0; +    /* +     * Close the file descriptor if no medium is present and open it to poll +     * again.  This ensures the medium size is refreshed.  If the file +     * descriptor is kept open the size can become stale.  This is essentially +     * replicating CD-ROM polling but is driven by the guest.  As the guest +     * polls, we poll the host. +     */ + +    if (s->fd == -1) { +        s->fd = qemu_open(bs->filename, s->open_flags, 0644); +        if (s->fd < 0) { +            return 0; +        } +    } + +    ret = (ioctl(s->fd, CDROM_DRIVE_STATUS, CDSL_CURRENT) == CDS_DISC_OK); + +    if (!ret) { +        close(s->fd); +        s->fd = -1; +    } +    return ret;  }  static int cdrom_eject(BlockDriverState *bs, int eject_flag) -- 1.7.4.1