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Re: [libvirt] [PATCH] Implement vol delete for disk pools



On Mon, Aug 11, 2008 at 03:58:41PM -0400, Cole Robinson wrote:
> The patch below implements virStorageVolDelete for volumes
> on a disk pool.
> 
> The only interesting thing here is that parted wants a
> partition number to delete, so we need to peel off the
> end of the volume's target path which will be of the form
> '/dev/sda1' or similar (I assume. If not, it's still
> better than having nothing implemented).
> 
> Thanks,
> Cole

> diff --git a/src/storage_backend_disk.c b/src/storage_backend_disk.c
> index dac827b..28e0a52 100644
> --- a/src/storage_backend_disk.c
> +++ b/src/storage_backend_disk.c
> @@ -22,11 +22,13 @@
>   */
>  
>  #include <config.h>
> +#include <string.h>
>  
>  #include "internal.h"
>  #include "storage_backend_disk.h"
>  #include "util.h"
>  #include "memory.h"
> +#include "c-ctype.h"
>  
>  enum {
>      VIR_STORAGE_POOL_DISK_DOS = 0,
> @@ -416,13 +418,6 @@ virStorageBackendDiskBuildPool(virConnectPtr conn,
>      return 0;
>  }
>  
> -
> -static int
> -virStorageBackendDiskDeleteVol(virConnectPtr conn,
> -                               virStoragePoolObjPtr pool,
> -                               virStorageVolDefPtr vol,
> -                               unsigned int flags);
> -
>  static int
>  virStorageBackendDiskCreateVol(virConnectPtr conn,
>                                 virStoragePoolObjPtr pool,
> @@ -486,14 +481,41 @@ virStorageBackendDiskCreateVol(virConnectPtr conn,
>  
>  static int
>  virStorageBackendDiskDeleteVol(virConnectPtr conn,
> -                               virStoragePoolObjPtr pool ATTRIBUTE_UNUSED,
> -                               virStorageVolDefPtr vol ATTRIBUTE_UNUSED,
> +                               virStoragePoolObjPtr pool,
> +                               virStorageVolDefPtr vol,
>                                 unsigned int flags ATTRIBUTE_UNUSED)
>  {
> -    /* delete a partition */
> -    virStorageReportError(conn, VIR_ERR_NO_SUPPORT,
> -                          _("Disk pools are not yet supported"));
> -    return -1;
> +    char *part_num = NULL;
> +    int i;
> +
> +    /* Strip target path (ex. '/dev/sda1') of its partition number */
> +    for (i = (strlen(vol->target.path)-1); i >= 0; --i) {
> +        if (!c_isdigit(vol->target.path[i]))
> +            break;
> +        part_num = &(vol->target.path[i]);
> +    }
> +
> +    if (!part_num) {
> +        virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
> +                              _("cannot parse partition number from target "
> +                                "path '%s'"), vol->target.path);
> +        return -1;
> +    }

This isn't correct because the target path is not guarenteed to point to
the master device name /dev/sda1.  The user could have configured it to
use a stable path such as /dev/disk/by-uuid/4cb23887-0d02-4e4c-bc95-7599c85afc1a

So, you need to first call 'readlink' on the vol->target.path, ignoring
EINVAL which you'll get if it wasn't a symlink. Once you've done that
you'll need to validate that it is sane by checking that vol->source.devices[0]
is a prefix of the resolved pathname. Finally, you can extract the partition
number. So something along the lines of

       char devname[PATH_MAX];

       if (readlink(vol->target.path, devname, sizeof(devname)) < 0 &&
           errno != EINVAL)
            virStorageReportError(...)

       if (!STRPREFIX(devname, vol->source.devices[0].path))
            virStorageReportError(....)

       part_num = devname + strlen(vol->source.devices[0].path)


> +
> +    /* eg parted /dev/sda rm 2 */
> +    const char *prog[] = {
> +        PARTED,
> +        pool->def->source.devices[0].path,
> +        "rm",
> +        "--script",
> +        part_num,
> +        NULL,
> +    };
> +


Daniel
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