[libvirt] [PATCH] Allow relative path for qemu backing file

[Eric Blake]

On 03/27/2011 07:30 PM, Jesse Cook wrote:
> This patch enables the relative backing file path support provided by
> qemu-img create.
> 
> If a relative path is specified for the backing file, it is converted
> to an absolute path using the storage pool path. The absolute path is
> used to verify that the backing file exists. If the backing file exists,
> the relative path is allowed and will be provided to qemu-img create.
> 
> This patch takes the place of a previous patch:
>   http://www.redhat.com/archives/libvir-list/2011-March/msg00179.html
> ---
>  src/storage/storage_backend.c |   18 +++++++++++++++++-
>  1 files changed, 17 insertions(+), 1 deletions(-)

Sorry for not reviewing this in time for 0.9.0.

> @@ -686,7 +689,20 @@ virStorageBackendCreateQemuImg(virConnectPtr conn,
>                                    vol->backingStore.format);
>              return -1;
>          }
> -        if (access(vol->backingStore.path, R_OK) != 0) {
> +
> +        /* Convert relative backing store paths to absolute paths for access
> +         * validation.
> +         */
> +        if ('/' != *(vol->backingStore.path)) {
> +            virAsprintf(&absolutePath, "%s/%s", pool->def->target.path,
> +                        vol->backingStore.path);
> +
> +        } else {
> +            virAsprintf(&absolutePath, "%s", vol->backingStore.path);

strdup is more efficient here, and avoiding malloc in the first place
even more so.

> +        }
> +        accessRetCode = access(absolutePath, R_OK);

This could segfault on OOM.

> +        VIR_FREE(absolutePath);
> +        if (accessRetCode != 0) {
>              virReportSystemError(errno,
>                                   _("inaccessible backing store volume %s"),
>                                   vol->backingStore.path);

ACK with nits fixed; so here's what I squashed in before pushing.  I
also updated AUTHORS to pass 'make syntax-check'; feel free to let me
know off-list if you prefer any alternate spelling there (especially
since you sent v1 and v2 under different email aliases).

diff --git i/src/storage/storage_backend.c w/src/storage/storage_backend.c
index 5f5565b..8af2878 100644
--- i/src/storage/storage_backend.c
+++ w/src/storage/storage_backend.c
@@ -693,7 +693,6 @@ virStorageBackendCreateQemuImg(virConnectPtr conn,

     if (vol->backingStore.path) {
         int accessRetCode = -1;
-
         char *absolutePath = NULL;

         /* XXX: Not strictly required: qemu-img has an option a different
@@ -719,14 +718,14 @@ virStorageBackendCreateQemuImg(virConnectPtr conn,
         /* Convert relative backing store paths to absolute paths for
access
          * validation.
          */
-        if ('/' != *(vol->backingStore.path)) {
+        if ('/' != *(vol->backingStore.path) &&
             virAsprintf(&absolutePath, "%s/%s", pool->def->target.path,
-                        vol->backingStore.path);
-
-        } else {
-            virAsprintf(&absolutePath, "%s", vol->backingStore.path);
+                        vol->backingStore.path) < 0) {
+            virReportOOMError();
+            return -1;
         }
-        accessRetCode = access(absolutePath, R_OK);
+        accessRetCode = access(absolutePath ? absolutePath
+                               : vol->backingStore.path, R_OK);
         VIR_FREE(absolutePath);
         if (accessRetCode != 0) {
             virReportSystemError(errno,


-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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