Re: [libvirt] [PATCH 1/2] Storage: Introduce shadow vol for refresh while the main vol builds.

From: Prerna Saxena <prerna(a)linux.vnet.ibm.com&gt; Date: Thu, 18 Jun 2015 05:05:09 -0500 Libvirt periodically refreshes all volumes in a storage pool, including the volumes being cloned. While cloning a storage volume from parent, we drop pool locks. Subsequent volume refresh sometimes changes allocation for an ongoing copy, and leads to corrupt images. Fix: Introduce a shadow volume that isolates the volume object under refresh from the base which has a copy ongoing. Signed-off-by: Prerna Saxena <prerna(a)linux.vnet.ibm.com&gt; --- src/storage/storage_driver.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c index 57060ab..4980546 100644 --- a/src/storage/storage_driver.c +++ b/src/storage/storage_driver.c @@ -1898,7 +1898,7 @@ storageVolCreateXMLFrom(virStoragePoolPtr obj, { virStoragePoolObjPtr pool, origpool = NULL; virStorageBackendPtr backend; - virStorageVolDefPtr origvol = NULL, newvol = NULL; + virStorageVolDefPtr origvol = NULL, newvol = NULL, shadowvol = NULL; virStorageVolPtr ret = NULL, volobj = NULL; unsigned long long allocation; int buildret; @@ -2010,6 +2010,17 @@ storageVolCreateXMLFrom(virStoragePoolPtr obj, if (backend->createVol(obj->conn, pool, newvol) < 0) goto cleanup; + /* Make a shallow copy of the 'defined' volume definition, since the + * original allocation value will change as the user polls 'info', + * but we only need the initial requested values + */ + if (VIR_ALLOC(shadowvol) < 0) { + newvol = NULL;

+ goto cleanup; + } + + memcpy(shadowvol, newvol, sizeof(*newvol)); + pool->volumes.objs[pool->volumes.count++] = newvol; volobj = virGetStorageVol(obj->conn, pool->def->name, newvol->name, newvol->key, NULL, NULL); @@ -2029,7 +2040,7 @@ storageVolCreateXMLFrom(virStoragePoolPtr obj, virStoragePoolObjUnlock(origpool); } - buildret = backend->buildVolFrom(obj->conn, pool, newvol, origvol, flags); + buildret = backend->buildVolFrom(obj->conn, pool, shadowvol, origvol, flags);