[libvirt] [PATCH v3] storageVolCreateXMLFrom: Allow multiple accesses to origvol

[Michal Privoznik]

When creating a new volume, it is possible to copy data into it from
another already existing volume (referred to as @origvol). Obviously,
the read-only access to @origvol is required, which is thread safe
(probably not performance-wise though). However, with current code
both @newvol and @origvol are marked as building for the time of
copying data from the @origvol to @newvol. The rationale behind
is to disallow some operations on both @origvol and @newvol, e.g.
vol-wipe, vol-delete, vol-download. While it makes sense to not allow
such operations on partly copied mirror, but it doesn't make sense to
disallow vol-create on the source (@origvol).

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---

diff to v2:
- changed the error message if volume is in use
- reworded commit message

 src/conf/storage_conf.h      |  1 +
 src/storage/storage_driver.c | 32 ++++++++++++++++++++++++++++++--
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/src/conf/storage_conf.h b/src/conf/storage_conf.h
index 9ad38e1..eae959c 100644
--- a/src/conf/storage_conf.h
+++ b/src/conf/storage_conf.h
@@ -64,6 +64,7 @@ struct _virStorageVolDef {
     int type; /* enum virStorageVolType */
 
     unsigned int building;
+    unsigned int in_use;
 
     virStorageVolSource source;
     virStorageSource target;
diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
index 2cb8347..542b382 100644
--- a/src/storage/storage_driver.c
+++ b/src/storage/storage_driver.c
@@ -1640,6 +1640,13 @@ storageVolDelete(virStorageVolPtr obj,
     if (virStorageVolDeleteEnsureACL(obj->conn, pool->def, vol) < 0)
         goto cleanup;
 
+    if (vol->in_use) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       _("volume '%s' is still in use."),
+                       vol->name);
+        goto cleanup;
+    }
+
     if (vol->building) {
         virReportError(VIR_ERR_OPERATION_INVALID,
                        _("volume '%s' is still being allocated."),
@@ -1912,8 +1919,8 @@ storageVolCreateXMLFrom(virStoragePoolPtr obj,
 
     /* Drop the pool lock during volume allocation */
     pool->asyncjobs++;
-    origvol->building = 1;
     newvol->building = 1;
+    origvol->in_use++;
     virStoragePoolObjUnlock(pool);
 
     if (origpool) {
@@ -1929,7 +1936,7 @@ storageVolCreateXMLFrom(virStoragePoolPtr obj,
         virStoragePoolObjLock(origpool);
     storageDriverUnlock(driver);
 
-    origvol->building = 0;
+    origvol->in_use--;
     newvol->building = 0;
     allocation = newvol->target.allocation;
     pool->asyncjobs--;
@@ -2076,6 +2083,13 @@ storageVolUpload(virStorageVolPtr obj,
     if (virStorageVolUploadEnsureACL(obj->conn, pool->def, vol) < 0)
         goto cleanup;
 
+    if (vol->in_use) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       _("volume '%s' is still in use."),
+                       vol->name);
+        goto cleanup;
+    }
+
     if (vol->building) {
         virReportError(VIR_ERR_OPERATION_INVALID,
                        _("volume '%s' is still being allocated."),
@@ -2167,6 +2181,13 @@ storageVolResize(virStorageVolPtr obj,
     if (virStorageVolResizeEnsureACL(obj->conn, pool->def, vol) < 0)
         goto cleanup;
 
+    if (vol->in_use) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       _("volume '%s' is still in use."),
+                       vol->name);
+        goto cleanup;
+    }
+
     if (vol->building) {
         virReportError(VIR_ERR_OPERATION_INVALID,
                        _("volume '%s' is still being allocated."),
@@ -2474,6 +2495,13 @@ storageVolWipePattern(virStorageVolPtr obj,
     if (virStorageVolWipePatternEnsureACL(obj->conn, pool->def, vol) < 0)
         goto cleanup;
 
+    if (vol->in_use) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       _("volume '%s' is still in use."),
+                       vol->name);
+        goto cleanup;
+    }
+
     if (vol->building) {
         virReportError(VIR_ERR_OPERATION_INVALID,
                        _("volume '%s' is still being allocated."),
-- 
1.9.0