[libvirt] [PATCH v4 2/4] storage: report error rather than warning if backing files doesn't exist

[Ján Tomko]

On 07/02/2013 11:35 AM, Guannan Ren wrote:
> If one of backing files for disk source doesn't exist, the guest will not
> be able to find and use the disk even though the disk still exists in
> guest xml definition. So reporting an error make more sense.
> 
> Adding virFileAccessibleAs() to check if the backing file described in
> disk meta exist in real path. If not, report error. the uid and gid
> arguments don't have so much meannings for F_OK, so give 0 for them.
> ---
>  src/util/virstoragefile.c | 23 +++++++++++++++--------
>  tests/virstoragetest.c    | 16 ++++++++--------
>  2 files changed, 23 insertions(+), 16 deletions(-)
> 
> diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
> index 27aa4fe..cb61e5b 100644
> --- a/src/util/virstoragefile.c
> +++ b/src/util/virstoragefile.c

> @@ -870,14 +877,10 @@ virStorageFileGetMetadataInternal(const char *path,
>                                         !!directory, backing,
>                                         &meta->directory,
>                                         &meta->backingStore) < 0) {
> -                    /* the backing file is (currently) unavailable, treat this
> -                     * file as standalone:
> -                     * backingStoreRaw is kept to mark broken image chains */
> -                    meta->backingStoreIsFile = false;
> -                    backingFormat = VIR_STORAGE_FILE_NONE;
> -                    VIR_WARN("Backing file '%s' of image '%s' is missing.",
> -                             meta->backingStoreRaw, path);
> -
> +                    VIR_ERROR(_("Backing file '%s' of image '%s' is missing."),
> +                              meta->backingStoreRaw, path);
> +                    VIR_FREE(backing);
> +                    goto cleanup;
>                  }
>              }
>              VIR_FREE(backing);

This change means you won't be able to start the pool if one of the files is
missing a backing file. I've forwarded a patch [1] from/for [2] that ignores
missing files on pool start and there is a bug [3] requesting that we ignore
other files as well. I feel like this is going in the other direction.

Wouldn't it be enough to check for them on domain start-up and leave the pool
running even if one of those volumes doesn't have an existing backing file?

Jan

[1] https://www.redhat.com/archives/libvir-list/2013-July/msg00635.html
[2] https://bugzilla.redhat.com/show_bug.cgi?id=977706
[3] https://bugzilla.redhat.com/show_bug.cgi?id=710866