Use the extract backing store format in storage volume lookup

The storage volume lookup code was probing for the backing store
format, instead of using the format extracted from the file
itself. This meant it could report in accurate information. If
a format is included in the file, then use that in preference,
with probing as a fallback.

* src/storage/storage_backend_fs.c: Use extracted backing store
  format

src/storage/storage_backend_fs.c

@@ -51,6 +51,7 @@
 static int
 virStorageBackendProbeTarget(virStorageVolTargetPtr target,
                              char **backingStore,
+                             int *backingStoreFormat,
                              unsigned long long *allocation,
                              unsigned long long *capacity,
                              virStorageEncryptionPtr *encryption)
@@ -58,6 +59,10 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
     int fd, ret;
     virStorageFileMetadata meta;
 
+    if (backingStore)
+        *backingStore = NULL;
+    if (backingStoreFormat)
+        *backingStoreFormat = VIR_STORAGE_FILE_AUTO;
     if (encryption)
         *encryption = NULL;
 
@@ -89,22 +94,30 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
 
     close(fd);
 
-    if (backingStore) {
-        *backingStore = meta.backingStore;
-        meta.backingStore = NULL;
+    if (meta.backingStore) {
+        if (backingStore) {
+            *backingStore = meta.backingStore;
+            meta.backingStore = NULL;
+            if (meta.backingStoreFormat == VIR_STORAGE_FILE_AUTO) {
+                if ((*backingStoreFormat = virStorageFileProbeFormat(*backingStore)) < 0) {
+                    close(fd);
+                    goto cleanup;
+                }
+            } else {
+                *backingStoreFormat = meta.backingStoreFormat;
+            }
+        } else {
+            VIR_FREE(meta.backingStore);
+        }
     }
 
-    VIR_FREE(meta.backingStore);
-
     if (capacity && meta.capacity)
         *capacity = meta.capacity;
 
     if (encryption != NULL && meta.encrypted) {
         if (VIR_ALLOC(*encryption) < 0) {
             virReportOOMError();
-            if (backingStore)
-                VIR_FREE(*backingStore);
-            return -1;
+            goto cleanup;
         }
 
         switch (target->format) {
@@ -124,6 +137,11 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
     }
 
     return 0;
+
+cleanup:
+    if (backingStore)
+        VIR_FREE(*backingStore);
+    return -1;
 }
 
 #if WITH_STORAGE_FS
@@ -585,6 +603,7 @@ virStorageBackendFileSystemRefresh(virConnectPtr conn ATTRIBUTE_UNUSED,
     while ((ent = readdir(dir)) != NULL) {
         int ret;
         char *backingStore;
+        int backingStoreFormat;
 
         if (VIR_ALLOC(vol) < 0)
             goto no_memory;
@@ -604,6 +623,7 @@ virStorageBackendFileSystemRefresh(virConnectPtr conn ATTRIBUTE_UNUSED,
 
         if ((ret = virStorageBackendProbeTarget(&vol->target,
                                                 &backingStore,
+                                                &backingStoreFormat,
                                                 &vol->allocation,
                                                 &vol->capacity,
                                                 &vol->target.encryption)) < 0) {
@@ -619,46 +639,18 @@ virStorageBackendFileSystemRefresh(virConnectPtr conn ATTRIBUTE_UNUSED,
         }
 
         if (backingStore != NULL) {
-            if (vol->target.format == VIR_STORAGE_FILE_QCOW2 &&
-                STRPREFIX("fmt:", backingStore)) {
-                char *fmtstr = backingStore + 4;
-                char *path = strchr(fmtstr, ':');
-                if (!path) {
-                    VIR_FREE(backingStore);
-                } else {
-                    *path = '\0';
-                    if ((vol->backingStore.format =
-                         virStorageFileFormatTypeFromString(fmtstr)) < 0) {
-                        VIR_FREE(backingStore);
-                    } else {
-                        memmove(backingStore, path, strlen(path) + 1);
-                        vol->backingStore.path = backingStore;
-
-                        if (virStorageBackendUpdateVolTargetInfo(&vol->backingStore,
-                                                                 NULL,
-                                                                 NULL) < 0)
-                            VIR_FREE(vol->backingStore);
-                    }
-                }
-            } else {
-                vol->backingStore.path = backingStore;
-
-                if ((ret = virStorageBackendProbeTarget(&vol->backingStore,
-                                                        NULL, NULL, NULL,
-                                                        NULL)) < 0) {
-                    if (ret == -1)
-                        goto cleanup;
-                    else {
-                        /* Silently ignore non-regular files,
-                         * eg '.' '..', 'lost+found' */
-                        VIR_FREE(vol->backingStore);
-                    }
-                }
+            vol->backingStore.path = backingStore;
+            vol->backingStore.format = backingStoreFormat;
+
+            if (virStorageBackendUpdateVolTargetInfo(&vol->backingStore,
+                                                     NULL,
+                                                     NULL) < 0) {
+                VIR_FREE(vol->backingStore.path);
+                goto cleanup;
             }
         }
 
 
-
         if (VIR_REALLOC_N(pool->volumes.objs,
                           pool->volumes.count+1) < 0)
             goto no_memory;