[libvirt] [PATCH v2 1/2] storage: Don't update volume objs list before we successfully create one

[Martin Kletzander]

On Thu, May 28, 2015 at 05:29:54PM +0200, Erik Skultety wrote:
>We do update pool volume object list before we actually create any
>volume. If buildVol fails, we then try to delete the volume in the
>storage as well as remove it from our structures. The problem is, that
>any backend that supports both buildVol and deleteVol would fail in this
>case which is completely unnecessary. This patch causes the update to
>take place after we know a volume has been created successfully, thus no
>removal in case of a buildVol failure is necessary.
>
>https://bugzilla.redhat.com/show_bug.cgi?id=1223177
>---
> src/storage/storage_driver.c | 31 +++++++++++++------------------
> 1 file changed, 13 insertions(+), 18 deletions(-)
>
>diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
>index ac4a74a..25a9656 100644
>--- a/src/storage/storage_driver.c
>+++ b/src/storage/storage_driver.c
>@@ -1,7 +1,7 @@
> /*
>  * storage_driver.c: core driver for storage APIs
>  *
>- * Copyright (C) 2006-2014 Red Hat, Inc.
>+ * Copyright (C) 2006-2015 Red Hat, Inc.
>  * Copyright (C) 2006-2008 Daniel P. Berrange
>  *
>  * This library is free software; you can redistribute it and/or
>@@ -1812,9 +1812,6 @@ storageVolCreateXML(virStoragePoolPtr obj,
>         goto cleanup;
>     }
>
>-    if (VIR_REALLOC_N(pool->volumes.objs,
>-                      pool->volumes.count+1) < 0)
>-        goto cleanup;
>
>     if (!backend->createVol) {
>         virReportError(VIR_ERR_NO_SUPPORT,
>@@ -1832,14 +1829,6 @@ storageVolCreateXML(virStoragePoolPtr obj,
>     if (backend->createVol(obj->conn, pool, voldef) < 0)
>         goto cleanup;
>
>-    pool->volumes.objs[pool->volumes.count++] = voldef;
>-    volobj = virGetStorageVol(obj->conn, pool->def->name, voldef->name,
>-                              voldef->key, NULL, NULL);
>-    if (!volobj) {
>-        pool->volumes.count--;
>-        goto cleanup;
>-    }
>-
>     if (VIR_ALLOC(buildvoldef) < 0) {
>         voldef = NULL;
>         goto cleanup;
>@@ -1868,14 +1857,20 @@ storageVolCreateXML(virStoragePoolPtr obj,
>         voldef->building = false;
>         pool->asyncjobs--;
>
>-        if (buildret < 0) {
>-            VIR_FREE(buildvoldef);
>-            storageVolDeleteInternal(volobj, backend, pool, voldef,
>-                                     0, false);
>-            voldef = NULL;
>+        if (buildret < 0)
>             goto cleanup;
>-        }
>+    }
>+
>+    if (VIR_REALLOC_N(pool->volumes.objs,
>+                      pool->volumes.count+1) < 0)
>+        goto cleanup;
>
>+    pool->volumes.objs[pool->volumes.count++] = voldef;
>+    volobj = virGetStorageVol(obj->conn, pool->def->name, voldef->name,
>+                              voldef->key, NULL, NULL);

I know it's pre-existing, but if you switch these two lines, you don't
have to do this unnecessary complicated cleanup (i.e. two lines) here.

>+    if (!volobj) {
>+        pool->volumes.count--;
>+        goto cleanup;

Also, if this fails, you need to delete the the volume anyway,
otherwise you have data inconsistency again.  How about doing this:

  VIR_REALLOC_N(pool->volumes.objs, ...);
  virGetStorageVol(...);
  buildVol();

This way the last thing that can fail is the one you don't want to
revert, but because it is the last one already, you don't need to
revert it (adding the definition to the list and increasing the count
can't fail).

>     }
>
>     if (backend->refreshVol &&
>--
>1.9.3
>
>--
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>libvir-list at redhat.com
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