kvm: look RBD volumes up through librbd instead of refreshing the whole pool

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/storage/LibvirtStorageAdaptor.java

@@ -659,6 +659,19 @@ public KVMStoragePool getStoragePool(String uuid, boolean refreshInfo) {
     public KVMPhysicalDisk getPhysicalDisk(String volumeUuid, KVMStoragePool pool) {
         LibvirtStoragePool libvirtPool = (LibvirtStoragePool)pool;
 
+        /*
+         * An RBD volume is looked up through librbd rather than through libvirt.
+         * A volume that was created by another host is not in the libvirt pool
+         * cache, so looking it up through libvirt misses and forces a refresh of
+         * the whole pool. Refreshing an RBD pool stats every image in it, so that
+         * cost grows with the number of volumes in the pool and is paid on every
+         * VM start. Every other RBD operation in this class already uses librbd
+         * directly.
+         */
+        if (pool.getType() == StoragePoolType.RBD) {
+            return getRbdPhysicalDisk(volumeUuid, libvirtPool);
+        }
+
         try {
             StorageVol vol = getVolume(libvirtPool.getPool(), volumeUuid);
             KVMPhysicalDisk disk;
@@ -696,6 +709,74 @@ public KVMPhysicalDisk getPhysicalDisk(String volumeUuid, KVMStoragePool pool) {
         }
     }
 
+    /**
+     * Looks an RBD volume up directly through librbd.
+     *
+     * The size reported by librbd is used for both the size and the virtual size of
+     * the disk, matching what this class already does after converting an image into
+     * an RBD volume.
+     */
+    private KVMPhysicalDisk getRbdPhysicalDisk(String volumeUuid, LibvirtStoragePool pool) {
+        Rados r = new Rados(pool.getAuthUserName());
+        try {
+            r.confSet("mon_host", pool.getSourceHost() + ":" + pool.getSourcePort());
+            /*
+             * The secret is null when the pool has no cephx user, and librados
+             * aborts the process rather than returning an error if it is handed a
+             * null value here.
+             */
+            if (pool.getAuthUserName() != null) {
+                r.confSet("key", pool.getAuthSecret());
+            } else {
+                r.confSet("auth_client_required", "none");
+            }
+            r.confSet("client_mount_timeout", "30");
+            r.connect();
+
+            IoCTX io = r.ioCtxCreate(pool.getSourceDir());
+            try {
+                Rbd rbd = new Rbd(io);
+                // The image is only stat'ed, so it is opened read only and cannot take the exclusive lock.
+                RbdImage image = rbd.openReadOnly(volumeUuid);
+                try {
+                    RbdImageInfo rbdInfo = image.stat();
+                    KVMPhysicalDisk disk = new KVMPhysicalDisk(pool.getSourceDir() + "/" + volumeUuid, volumeUuid, pool);
+                    disk.setFormat(PhysicalDiskFormat.RAW);
+                    disk.setSize(rbdInfo.size);
+                    disk.setVirtualSize(rbdInfo.size);
+                    return disk;
+                } finally {
+                    closeRbdImage(rbd, image, volumeUuid);
+                }
+            } finally {
+                r.ioCtxDestroy(io);
+            }
+        } catch (RadosException e) {
+            logger.error("A Ceph RADOS operation failed (" + e.getReturnValue() + "). The error was: " + e.getMessage()
+                    + " - " + ErrorCode.getErrorMessage(e.getReturnValue()));
+            throw new CloudRuntimeException(e.toString(), e);
+        } catch (RbdException e) {
+            logger.error("A Ceph RBD operation failed (" + e.getReturnValue() + "). The error was: " + e.getMessage()
+                    + " - " + ErrorCode.getErrorMessage(e.getReturnValue()));
+            throw new CloudRuntimeException(e.toString(), e);
+        } finally {
+            r.shutDown();
+        }
+    }
+
+    /**
+     * Closes an RBD image without throwing, so that a failure to close cannot discard a
+     * successful result or hide the exception that is already on its way out.
+     */
+    private void closeRbdImage(Rbd rbd, RbdImage image, String volumeUuid) {
+        try {
+            rbd.close(image);
+        } catch (RbdException e) {
+            logger.warn("Failed to close RBD image " + volumeUuid + " (" + e.getReturnValue() + "): "
+                    + e.getMessage() + " - " + ErrorCode.getErrorMessage(e.getReturnValue()));
+        }
+    }
+
     /**
      * adjust refcount
      */