[libvirt] [PATCH v2] logical: Check for existing vgname before building

[John Ferlan]

https://bugzilla.redhat.com/show_bug.cgi?id=1373711

Add a check for an existing volume group name before trying to build
the volume group. Since the process of building a vg involves wiping
the first 512 bytes and using pvcreate on each source device path before
creating the vg - we could conceivably overwrite something that we
shouldn't be. Also, once a pv is part of a vg, the pvcreate would fail
unless we chose to overwrite the volume.

Signed-off-by: John Ferlan <jferlan at redhat.com>
---

 Difference w/ v2 is that I'm taking a different approach - disallow the
 second pool-build since the vg already exists.  NB: libvirt has no API
 to extend an existing vg - that's left to an admin anyway.

 src/storage/storage_backend_logical.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/storage/storage_backend_logical.c b/src/storage/storage_backend_logical.c
index ca05fe1..b241495 100644
--- a/src/storage/storage_backend_logical.c
+++ b/src/storage/storage_backend_logical.c
@@ -682,14 +682,31 @@ virStorageBackendLogicalBuildPool(virConnectPtr conn ATTRIBUTE_UNUSED,
                                   virStoragePoolObjPtr pool,
                                   unsigned int flags)
 {
-    virCommandPtr vgcmd;
+    virCommandPtr vgcmd = NULL;
     int fd;
     char zeros[PV_BLANK_SECTOR_SIZE];
     int ret = -1;
     size_t i;
+    virStoragePoolSourceList sourceList;
 
     virCheckFlags(0, -1);
 
+    /* Let's make sure the about to be created vg doesn't already exist */
+    memset(&sourceList, 0, sizeof(sourceList));
+    sourceList.type = VIR_STORAGE_POOL_LOGICAL;
+
+    if (virStorageBackendLogicalGetPoolSources(&sourceList) < 0)
+        return -1;
+
+    for (i = 0; i < sourceList.nsources; i++) {
+        if (STREQ(sourceList.sources[i].name, pool->def->source.name)) {
+            virReportError(VIR_ERR_STORAGE_POOL_BUILT,
+                           _("volume group with name '%s' already exists"),
+                           pool->def->source.name);
+            goto cleanup;
+        }
+    }
+
     memset(zeros, 0, sizeof(zeros));
 
     vgcmd = virCommandNewArgList(VGCREATE, pool->def->source.name, NULL);
@@ -751,6 +768,9 @@ virStorageBackendLogicalBuildPool(virConnectPtr conn ATTRIBUTE_UNUSED,
     ret = 0;
 
  cleanup:
+    for (i = 0; i < sourceList.nsources; i++)
+        virStoragePoolSourceClear(&sourceList.sources[i]);
+    VIR_FREE(sourceList.sources);
     virCommandFree(vgcmd);
     return ret;
 }
-- 
2.7.4