[libvirt] [PATCH 11/35] util: file: Add helper to determine whether a path is a CDROM

[John Ferlan]

On 04/25/2018 11:15 AM, Peter Krempa wrote:
> Add detection mechanism which will allow to check whether a path to a
> block device is a physical CDROM drive. This will be useful once we will
> need to pass it to hypervisors.
> 
> The linux implementation uses an ioctl to do the detection, while the
> fallback uses a simple string prefix match.
> 
> Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> ---
>  src/libvirt_private.syms |  1 +
>  src/util/virfile.c       | 56 +++++++++++++++++++++++++++++++++++++++++++++++-
>  src/util/virfile.h       |  2 ++
>  3 files changed, 58 insertions(+), 1 deletion(-)
> 

Should this be a replacement for qemuDomainFilePathIsHostCDROM used for
qemuDomainObjCheckDiskTaint?

Not a problem with this code, but I think there should only be one place
that we determine host CDROM and it doesn't matter to me the mechanism.
Just trying to avoid multiple means to get the same answer.

I'm going to stop here for now as it's late for me - besides the answer
here affects patch 12 too in a way.

John


> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index d2728749fb..4f911c10a8 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -1781,6 +1781,7 @@ virFileGetMountSubtree;
>  virFileHasSuffix;
>  virFileInData;
>  virFileIsAbsPath;
> +virFileIsCdrom;
>  virFileIsDir;
>  virFileIsExecutable;
>  virFileIsLink;
> diff --git a/src/util/virfile.c b/src/util/virfile.c
> index 24f866525f..ad59b7015b 100644
> --- a/src/util/virfile.c
> +++ b/src/util/virfile.c
> @@ -59,8 +59,9 @@
>  # include <sys/statfs.h>
>  # if HAVE_DECL_LO_FLAGS_AUTOCLEAR
>  #  include <linux/loop.h>
> -#  include <sys/ioctl.h>
>  # endif
> +# include <sys/ioctl.h>
> +# include <linux/cdrom.h>
>  #endif
> 
>  #include "configmake.h"
> @@ -1938,6 +1939,59 @@ int virFileIsMountPoint(const char *file)
>  }
> 
> 
> +#if defined(__linux__)
> +/**
> + * virFileIsCdrom:
> + * @filename: File to check
> + *
> + * Returns 1 if @filename is a cdrom device 0 if it is not a cdrom and -1 on
> + * error. 'errno' of the failure is preserved and no libvirt errors are
> + * reported.
> + */
> +int
> +virFileIsCdrom(const char *filename)
> +{
> +    struct stat st;
> +    int fd;
> +    int ret = -1;
> +
> +    if ((fd = open(filename, O_RDONLY | O_NONBLOCK)) < 0)
> +        goto cleanup;
> +
> +    if (fstat(fd, &st) < 0)
> +        goto cleanup;
> +
> +    if (!S_ISBLK(st.st_mode)) {
> +        ret = 0;
> +        goto cleanup;
> +    }
> +
> +    /* Attempt to detect via a CDROM specific ioctl */
> +    if (ioctl(fd, CDROM_DRIVE_STATUS, CDSL_CURRENT) >= 0)
> +        ret = 1;
> +    else
> +        ret = 0;
> +
> + cleanup:
> +    VIR_FORCE_CLOSE(fd);
> +    return ret;
> +}
> +
> +#else
> +
> +int
> +virFileIsCdrom(const char *filename)
> +{
> +    if (STRPREFIX(filename, "/dev/cd", NULL) ||
> +        STRPREFIX(filename, "/dev/acd", NULL))
> +        return 1;
> +
> +    return 0;
> +}
> +
> +#endif /* defined(__linux__) */
> +
> +
>  #if defined HAVE_MNTENT_H && defined HAVE_GETMNTENT_R
>  static int
>  virFileGetMountSubtreeImpl(const char *mtabpath,
> diff --git a/src/util/virfile.h b/src/util/virfile.h
> index cd2a3867c2..8ab7d2d6a6 100644
> --- a/src/util/virfile.h
> +++ b/src/util/virfile.h
> @@ -207,6 +207,8 @@ enum {
>  int virFileIsSharedFSType(const char *path, int fstypes) ATTRIBUTE_NONNULL(1);
>  int virFileIsSharedFS(const char *path) ATTRIBUTE_NONNULL(1);
>  int virFileIsMountPoint(const char *file) ATTRIBUTE_NONNULL(1);
> +int virFileIsCdrom(const char *filename)
> +    ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
> 
>  int virFileGetMountSubtree(const char *mtabpath,
>                             const char *prefix,
>