[libvirt] [PATCH] storage: Error out earlier if the volume target path already exists

[Osier Yang]

https://bugzilla.redhat.com/show_bug.cgi?id=832302

It's odd to fall through to buildVol, and the existed file is
removed when buildVol fails. This checks if the volume target
path already exists in createVol. The reason for not using
error like "Volume already exists" is that there isn't volume
maintained by libvirt for the path until a operation like
pool-refresh, using error like that will just cause confusion.

---
BTW, It inspires me again that perhaps we should integrate things
like inotify to storage.
---
 src/storage/storage_backend_fs.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/src/storage/storage_backend_fs.c b/src/storage/storage_backend_fs.c
index 4e6ebbf..6cddad0 100644
--- a/src/storage/storage_backend_fs.c
+++ b/src/storage/storage_backend_fs.c
@@ -1000,6 +1000,13 @@ virStorageBackendFileSystemVolCreate(virConnectPtr conn ATTRIBUTE_UNUSED,
         return -1;
     }
 
+    if (virFileExists(vol->target.path)) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       _("volume target path '%s' already exists"),
+                       vol->target.path);
+        return -1;
+    }
+
     VIR_FREE(vol->key);
     vol->key = strdup(vol->target.path);
     if (vol->key == NULL) {
-- 
1.7.7.6