[libvirt] [PATCH 12/12] qemu: domain: skip chain detection to end of backing chain

[John Ferlan]

On 10/20/2017 09:47 AM, Peter Krempa wrote:
> When a user provides the backing chain, we will not need to re-detect
> all the backing stores again, but should move to the end of the user
> specified chain. Additionally if a user provides a full terminated chain
> we should not attempt any further detection.
> ---
>  src/qemu/qemu_domain.c | 48 +++++++++++++++++++++++++++++++++++++++---------
>  1 file changed, 39 insertions(+), 9 deletions(-)
> 
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index 3560cdd29..5973474ca 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -6030,27 +6030,57 @@ qemuDomainDetermineDiskChain(virQEMUDriverPtr driver,
>                               bool report_broken)
>  {
>      virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
> -    int ret = 0;
> +    virStorageSourcePtr src = disk->src;
> +    int ret = -1;
>      uid_t uid;
>      gid_t gid;
> 
> -    if (virStorageSourceIsEmpty(disk->src))
> +    if (virStorageSourceIsEmpty(src)) {
> +        ret = 0;
>          goto cleanup;
> +    }
> 
>      if (virStorageSourceHasBacking(disk->src)) {

could this one be just @src?

> -        if (force_probe)
> -            virStorageSourceBackingStoreClear(disk->src);
> -        else
> -            goto cleanup;
> +        if (force_probe) {
> +            virStorageSourceBackingStoreClear(src);
> +        } else {
> +            /* skip to the end of the chain */
> +            while (virStorageSourceIsBacking(src)) {
> +                if (report_broken &&
> +                    virStorageFileSupportsAccess(src)) {
> +
> +                    if (qemuDomainStorageFileInit(driver, vm, src, disk->src) < 0)
> +                        goto cleanup;
> +
> +                    if (virStorageFileAccess(src, F_OK) < 0) {
> +                        virStorageFileReportBrokenChain(errno, src, disk->src);
> +                        virStorageFileDeinit(src);
> +                        goto cleanup;
> +                    }
> +
> +                    virStorageFileDeinit(src);
> +                }
> +                src = src->backingStore;
> +            }
> +        }
>      }
> 
> -    qemuDomainGetImageIds(cfg, vm, disk->src, NULL, &uid, &gid);
> +    /* We skipped to the end of the chain. Skip detection if there's the
> +     * terminator. (An allocated but empty backingStore) */
> +    if (src->backingStore) {
> +        ret = 0;
> +        goto cleanup;
> +    }
> +
> +    qemuDomainGetImageIds(cfg, vm, src, disk->src, &uid, &gid);
> 
> -    if (virStorageFileGetMetadata(disk->src,
> +    if (virStorageFileGetMetadata(src,
>                                    uid, gid,
>                                    cfg->allowDiskFormatProbing,
>                                    report_broken) < 0)
> -        ret = -1;
> +        goto cleanup;

> +
> +    ret = 0;
> 
>   cleanup:
>      virObjectUnref(cfg);
>