[libvirt] [PATCH 7/7] storageDriver: Use RW locks

[Michal Privoznik]

Currently, the storage driver doesn't have virStoragePoolList
object. It maintains the list itself. To mutually exclude two
threads trying to access it mutexes are used. However, this hurts
performance as there's no reason why two threads reading from the
list cannot run at the same time.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/conf/virstorageobj.h     |  2 +-
 src/storage/storage_driver.c | 42 +++++++++++++++++++++++-------------------
 2 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/src/conf/virstorageobj.h b/src/conf/virstorageobj.h
index 5a61b2aa6..585c63869 100644
--- a/src/conf/virstorageobj.h
+++ b/src/conf/virstorageobj.h
@@ -53,7 +53,7 @@ typedef struct _virStorageDriverState virStorageDriverState;
 typedef virStorageDriverState *virStorageDriverStatePtr;
 
 struct _virStorageDriverState {
-    virMutex lock;
+    virRWLock lock;
 
     virStoragePoolObjList pools;
 
diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
index f162f2e5a..b2ba667ef 100644
--- a/src/storage/storage_driver.c
+++ b/src/storage/storage_driver.c
@@ -70,11 +70,15 @@ struct _virStorageVolStreamInfo {
 
 static void storageDriverLock(void)
 {
-    virMutexLock(&driver->lock);
+    virRWLockWrite(&driver->lock);
+}
+static void storageDriverLockRead(void)
+{
+    virRWLockRead(&driver->lock);
 }
 static void storageDriverUnlock(void)
 {
-    virMutexUnlock(&driver->lock);
+    virRWLockUnlock(&driver->lock);
 }
 
 
@@ -253,7 +257,7 @@ storageStateInitialize(bool privileged,
     if (VIR_ALLOC(driver) < 0)
         return ret;
 
-    if (virMutexInit(&driver->lock) < 0) {
+    if (virRWLockInit(&driver->lock) < 0) {
         virReportSystemError(errno, "%s",
                              _("cannot initialize storage driver lock"));
         VIR_FREE(driver);
@@ -382,7 +386,7 @@ storageStateCleanup(void)
     VIR_FREE(driver->autostartDir);
     VIR_FREE(driver->stateDir);
     storageDriverUnlock();
-    virMutexDestroy(&driver->lock);
+    virRWLockDestroy(&driver->lock);
     VIR_FREE(driver);
 
     return 0;
@@ -417,7 +421,7 @@ virStoragePoolObjFromStoragePool(virStoragePoolPtr pool)
 {
     virStoragePoolObjPtr ret;
 
-    storageDriverLock();
+    storageDriverLockRead();
     ret = storagePoolObjFindByUUID(pool->uuid, pool->name);
     storageDriverUnlock();
 
@@ -430,7 +434,7 @@ storagePoolObjFindByName(const char *name)
 {
     virStoragePoolObjPtr obj;
 
-    storageDriverLock();
+    storageDriverLockRead();
     if (!(obj = virStoragePoolObjFindByName(&driver->pools, name)))
         virReportError(VIR_ERR_NO_STORAGE_POOL,
                        _("no storage pool with matching name '%s'"), name);
@@ -447,7 +451,7 @@ storagePoolLookupByUUID(virConnectPtr conn,
     virStoragePoolObjPtr obj;
     virStoragePoolPtr pool = NULL;
 
-    storageDriverLock();
+    storageDriverLockRead();
     obj = storagePoolObjFindByUUID(uuid, NULL);
     storageDriverUnlock();
     if (!obj)
@@ -511,7 +515,7 @@ storageConnectNumOfStoragePools(virConnectPtr conn)
     if (virConnectNumOfStoragePoolsEnsureACL(conn) < 0)
         return -1;
 
-    storageDriverLock();
+    storageDriverLockRead();
     nactive = virStoragePoolObjNumOfStoragePools(&driver->pools, conn, true,
                                                  virConnectNumOfStoragePoolsCheckACL);
     storageDriverUnlock();
@@ -530,7 +534,7 @@ storageConnectListStoragePools(virConnectPtr conn,
     if (virConnectListStoragePoolsEnsureACL(conn) < 0)
         return -1;
 
-    storageDriverLock();
+    storageDriverLockRead();
     got = virStoragePoolObjGetNames(&driver->pools, conn, true,
                                     virConnectListStoragePoolsCheckACL,
                                     names, maxnames);
@@ -546,7 +550,7 @@ storageConnectNumOfDefinedStoragePools(virConnectPtr conn)
     if (virConnectNumOfDefinedStoragePoolsEnsureACL(conn) < 0)
         return -1;
 
-    storageDriverLock();
+    storageDriverLockRead();
     nactive = virStoragePoolObjNumOfStoragePools(&driver->pools, conn, false,
                                                  virConnectNumOfDefinedStoragePoolsCheckACL);
     storageDriverUnlock();
@@ -565,7 +569,7 @@ storageConnectListDefinedStoragePools(virConnectPtr conn,
     if (virConnectListDefinedStoragePoolsEnsureACL(conn) < 0)
         return -1;
 
-    storageDriverLock();
+    storageDriverLockRead();
     got = virStoragePoolObjGetNames(&driver->pools, conn, false,
                                     virConnectListDefinedStoragePoolsCheckACL,
                                     names, maxnames);
@@ -1457,7 +1461,7 @@ storageVolLookupByKey(virConnectPtr conn,
     size_t i;
     virStorageVolPtr vol = NULL;
 
-    storageDriverLock();
+    storageDriverLockRead();
     for (i = 0; i < driver->pools.count && !vol; i++) {
         virStoragePoolObjLock(driver->pools.objs[i]);
         if (virStoragePoolObjIsActive(driver->pools.objs[i])) {
@@ -1502,7 +1506,7 @@ storageVolLookupByPath(virConnectPtr conn,
     if (!cleanpath)
         return NULL;
 
-    storageDriverLock();
+    storageDriverLockRead();
     for (i = 0; i < driver->pools.count && !vol; i++) {
         virStoragePoolObjPtr obj = driver->pools.objs[i];
         virStorageVolDefPtr voldef;
@@ -1597,7 +1601,7 @@ storagePoolLookupByTargetPath(virConnectPtr conn,
     if (!cleanpath)
         return NULL;
 
-    storageDriverLock();
+    storageDriverLockRead();
     for (i = 0; i < driver->pools.count && !pool; i++) {
         virStoragePoolObjPtr obj = driver->pools.objs[i];
 
@@ -1860,7 +1864,7 @@ storageVolCreateXML(virStoragePoolPtr pool,
 
         VIR_FREE(buildvoldef);
 
-        storageDriverLock();
+        storageDriverLockRead();
         virStoragePoolObjLock(obj);
         storageDriverUnlock();
 
@@ -1926,7 +1930,7 @@ storageVolCreateXMLFrom(virStoragePoolPtr pool,
                   VIR_STORAGE_VOL_CREATE_REFLINK,
                   NULL);
 
-    storageDriverLock();
+    storageDriverLockRead();
     obj = virStoragePoolObjFindByUUID(&driver->pools, pool->uuid);
     if (obj && STRNEQ(pool->name, volsrc->pool)) {
         virStoragePoolObjUnlock(obj);
@@ -2060,7 +2064,7 @@ storageVolCreateXMLFrom(virStoragePoolPtr pool,
 
     buildret = backend->buildVolFrom(pool->conn, obj, shadowvol, voldefsrc, flags);
 
-    storageDriverLock();
+    storageDriverLockRead();
     virStoragePoolObjLock(obj);
     if (objsrc)
         virStoragePoolObjLock(objsrc);
@@ -2624,7 +2628,7 @@ storageConnectListAllStoragePools(virConnectPtr conn,
     if (virConnectListAllStoragePoolsEnsureACL(conn) < 0)
         goto cleanup;
 
-    storageDriverLock();
+    storageDriverLockRead();
     ret = virStoragePoolObjListExport(conn, &driver->pools, pools,
                                       virConnectListAllStoragePoolsCheckACL,
                                       flags);
@@ -3029,7 +3033,7 @@ virStoragePoolObjFindPoolByUUID(const unsigned char *uuid)
 {
     virStoragePoolObjPtr obj;
 
-    storageDriverLock();
+    storageDriverLockRead();
     obj = virStoragePoolObjFindByUUID(&driver->pools, uuid);
     storageDriverUnlock();
     return obj;
-- 
2.13.0