storage_driver: Release pool object lock for some long running jobs

As advertised in previous commit, there are three APIs that might
run for quite some time (because they read/write data from/to a
volume) and these three are: downloadVol, uploadVol, wipeVol.
Release pool object lock and reacquire it later to allow more
concurrency.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

src/storage/storage_backend.h

@@ -64,18 +64,30 @@ typedef int (*virStorageBackendVolumeResize)(virStoragePoolObjPtr pool,
                                              virStorageVolDefPtr vol,
                                              unsigned long long capacity,
                                              unsigned int flags);
+
+/* Upon entering this callback passed @obj is unlocked. However,
+ * the pool's asyncjobs counter has been incremented and volume's
+ * in_use has been adjusted to ensure singular usage. */
 typedef int (*virStorageBackendVolumeDownload)(virStoragePoolObjPtr obj,
                                                virStorageVolDefPtr vol,
                                                virStreamPtr stream,
                                                unsigned long long offset,
                                                unsigned long long length,
                                                unsigned int flags);
+
+/* Upon entering this callback passed @obj is unlocked. However,
+ * the pool's asyncjobs counter has been incremented and volume's
+ * in_use has been adjusted to ensure singular usage. */
 typedef int (*virStorageBackendVolumeUpload)(virStoragePoolObjPtr obj,
                                              virStorageVolDefPtr vol,
                                              virStreamPtr stream,
                                              unsigned long long offset,
                                              unsigned long long len,
                                              unsigned int flags);
+
+/* Upon entering this callback passed @obj is unlocked. However,
+ * the pool's asyncjobs counter has been incremented and volume's
+ * in_use has been adjusted to ensure singular usage. */
 typedef int (*virStorageBackendVolumeWipe)(virStoragePoolObjPtr pool,
                                            virStorageVolDefPtr vol,
                                            unsigned int algorithm,

src/storage/storage_backend_iscsi_direct.c

@@ -693,7 +693,11 @@ virStorageBackenISCSIDirectWipeVol(virStoragePoolObjPtr pool,
 
     virCheckFlags(0, -1);
 
-    if (!(iscsi = virStorageBackendISCSIDirectSetConnection(pool, NULL)))
+    virObjectLock(pool);
+    iscsi = virStorageBackendISCSIDirectSetConnection(pool, NULL);
+    virObjectUnlock(pool);
+
+    if (!iscsi)
         return -1;
 
     switch ((virStorageVolWipeAlgorithm) algorithm) {

src/storage/storage_backend_rbd.c

@@ -1200,7 +1200,7 @@ virStorageBackendRBDVolWipe(virStoragePoolObjPtr pool,
                             unsigned int flags)
 {
     virStorageBackendRBDStatePtr ptr = NULL;
-    virStoragePoolDefPtr def = virStoragePoolObjGetDef(pool);
+    virStoragePoolDefPtr def;
     rbd_image_t image = NULL;
     rbd_image_info_t info;
     uint64_t stripe_count;
@@ -1209,9 +1209,13 @@ virStorageBackendRBDVolWipe(virStoragePoolObjPtr pool,
 
     virCheckFlags(0, -1);
 
+    virObjectLock(pool);
+    def = virStoragePoolObjGetDef(pool);
     VIR_DEBUG("Wiping RBD image %s/%s", def->source.name, vol->name);
+    ptr = virStorageBackendRBDNewState(pool);
+    virObjectUnlock(pool);
 
-    if (!(ptr = virStorageBackendRBDNewState(pool)))
+    if (!ptr)
         goto cleanup;
 
     if ((r = rbd_open(ptr->ioctx, vol->name, &image, NULL)) < 0) {

src/storage/storage_driver.c

@@ -2178,9 +2178,11 @@ storageVolDownload(virStorageVolPtr vol,
 
     virStoragePoolObjIncrAsyncjobs(obj);
     voldef->in_use++;
+    virObjectUnlock(obj);
 
     ret = backend->downloadVol(obj, voldef, stream, offset, length, flags);
 
+    virObjectLock(obj);
     voldef->in_use--;
     virStoragePoolObjDecrAsyncjobs(obj);
 
@@ -2378,9 +2380,11 @@ storageVolUpload(virStorageVolPtr vol,
 
     virStoragePoolObjIncrAsyncjobs(obj);
     voldef->in_use++;
+    virObjectUnlock(obj);
 
     rc = backend->uploadVol(obj, voldef, stream, offset, length, flags);
 
+    virObjectLock(obj);
     voldef->in_use--;
     virStoragePoolObjDecrAsyncjobs(obj);
 
@@ -2554,9 +2558,11 @@ storageVolWipePattern(virStorageVolPtr vol,
 
     virStoragePoolObjIncrAsyncjobs(obj);
     voldef->in_use++;
+    virObjectUnlock(obj);
 
     rc = backend->wipeVol(obj, voldef, algorithm, flags);
 
+    virObjectLock(obj);
     voldef->in_use--;
     virStoragePoolObjDecrAsyncjobs(obj);