[libvirt] [PATCH 1/1] storage: resize vol against real allocated size when --allocate is specified

[Wang Sen]

Currently, vol-resize allocates more bytes against vol->capacity, but
vol->capacity may be different from the real allocated size because --allocate
may not be specified. e.g.
	[root at localhost ~]# virsh vol-list --pool tmp-pool --details
	 name path type Capacity allocated
	-------------------------------------------------------------
	 tmp-vol  /root/tmp-pool/tmp-vol  file  1.00 GiB  1.00 GiB
	[root at localhost ~]# virsh vol-resize tmp-vol --pool tmp-pool 2G
	[root at localhost ~]# virsh vol-list --pool tmp-pool --details
	 name path type Capacity allocated
	-------------------------------------------------------------
	 tmp-vol  /root/tmp-pool/tmp-vol  file  2.00 GiB  1.00 GiB
So, if we want to allocate more bytes to 3G, the real allocated size is 2G
actually.
	[root at localhost ~]# virsh vol-resize tmp-vol --pool tmp-pool 3G --allocate
	[root at localhost ~]# virsh vol-list --pool tmp-pool --details
	 name path type Capacity allocated
	-------------------------------------------------------------
	 tmp-vol  /root/tmp-pool/tmp-vol  file  3.00 GiB  2.00 GiB
This patch enable resize vol against the real allocated size. After this patch
is applied, the result of the last resize command become 3G.
	[root at localhost ~]# virsh vol-resize tmp-vol --pool tmp-pool 3G --allocate
	[root at localhost ~]# virsh vol-list --pool tmp-pool --details
	 name path type Capacity allocated
	-------------------------------------------------------------
	 tmp-vol  /root/tmp-pool/tmp-vol  file  3.00 GiB  3.00 GiB

Signed-off-by: Wang Sen <wangsen at linux.vnet.ibm.com>
---
 src/storage/storage_backend_fs.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/storage/storage_backend_fs.c b/src/storage/storage_backend_fs.c
index 11cf2df..e75c57b 100644
--- a/src/storage/storage_backend_fs.c
+++ b/src/storage/storage_backend_fs.c
@@ -1261,13 +1261,28 @@ virStorageBackendFileSystemVolResize(virConnectPtr conn ATTRIBUTE_UNUSED,
                                      unsigned long long capacity,
                                      unsigned int flags)
 {
+    int fd = -1;
     virCheckFlags(VIR_STORAGE_VOL_RESIZE_ALLOCATE, -1);
+    unsigned long long orig_capacity;
+    virStorageFileMetadataPtr meta = NULL;
+
+    if ((fd = open(vol->target.path, O_RDWR)) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("Can not open file"));
+    }
+
+    if (!(meta =  virStorageFileGetMetadataFromFD(vol->target.path, fd, \
+                                                  vol->target.format))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("Get meta data error!"));
+    }
+    orig_capacity = meta->capacity;
+    virStorageFileFreeMetadata(meta);
+    close(fd);
 
     bool pre_allocate = flags & VIR_STORAGE_VOL_RESIZE_ALLOCATE;
 
     if (vol->target.format == VIR_STORAGE_FILE_RAW) {
         return virStorageFileResize(vol->target.path, capacity,
-                                    vol->capacity, pre_allocate);
+                                    orig_capacity, pre_allocate);
     } else {
         if (pre_allocate) {
             virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
-- 
1.8.3.1