[libvirt] [PATCH 2/2] Storage : Fix cloning of raw, sparse volumes

[Prerna Saxena]

From: Prerna Saxena <prerna at linux.vnet.ibm.com>
Date: Mon, 22 Jun 2015 02:54:32 -0500

When virsh vol-clone is attempted on a raw file where capacity > allocation,
the resulting cloned volume has a size that matches the virtual-size of
the parent; in place of matching its actual, disk size.
This patch fixes the cloned disk to have same _allocated_size_ as
the parent file from which it was cloned.

Ref: http://www.redhat.com/archives/libvir-list/2015-May/msg00050.html

Also fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1130739

Signed-off-by: Prerna Saxena <prerna at linux.vnet.ibm.com>
---
 src/storage/storage_backend.c | 10 +++++-----
 src/storage/storage_driver.c  |  5 -----
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
index ce59f63..c99b718 100644
--- a/src/storage/storage_backend.c
+++ b/src/storage/storage_backend.c
@@ -342,7 +342,7 @@ virStorageBackendCreateBlockFrom(virConnectPtr conn ATTRIBUTE_UNUSED,
         goto cleanup;
     }
 
-    remain = vol->target.allocation;
+    remain = vol->target.capacity;
 
     if (inputvol) {
         int res = virStorageBackendCopyToFD(vol, inputvol,
@@ -397,7 +397,7 @@ createRawFile(int fd, virStorageVolDefPtr vol,
               virStorageVolDefPtr inputvol,
               bool reflink_copy)
 {
-    bool need_alloc = true;
+    bool need_alloc = !(inputvol && (inputvol->target.capacity > inputvol->target.allocation));
     int ret = 0;
     unsigned long long remain;
 
@@ -420,7 +420,7 @@ createRawFile(int fd, virStorageVolDefPtr vol,
      * to writing zeroes block by block in case fallocate isn't
      * available, and since we're going to copy data from another
      * file it doesn't make sense to write the file twice. */
-    if (vol->target.allocation) {
+    if (vol->target.allocation && need_alloc) {
         if (fallocate(fd, 0, 0, vol->target.allocation) == 0) {
             need_alloc = false;
         } else if (errno != ENOSYS && errno != EOPNOTSUPP) {
@@ -433,14 +433,14 @@ createRawFile(int fd, virStorageVolDefPtr vol,
     }
 #endif
 
-    remain = vol->target.allocation;
+    remain = vol->target.capacity;
 
     if (inputvol) {
         /* allow zero blocks to be skipped if we've requested sparse
          * allocation (allocation < capacity) or we have already
          * been able to allocate the required space. */
         bool want_sparse = !need_alloc ||
-            (vol->target.allocation < inputvol->target.capacity);
+            (inputvol->target.allocation < inputvol->target.capacity);
 
         ret = virStorageBackendCopyToFD(vol, inputvol, fd, &remain,
                                         want_sparse, reflink_copy);
diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
index 4980546..c1dfe89 100644
--- a/src/storage/storage_driver.c
+++ b/src/storage/storage_driver.c
@@ -1976,11 +1976,6 @@ storageVolCreateXMLFrom(virStoragePoolPtr obj,
     if (newvol->target.capacity < origvol->target.capacity)
         newvol->target.capacity = origvol->target.capacity;
 
-    /* Make sure allocation is at least as large as the destination cap,
-     * to make absolutely sure we copy all possible contents */
-    if (newvol->target.allocation < origvol->target.capacity)
-        newvol->target.allocation = origvol->target.capacity;
-
     if (!backend->buildVolFrom) {
         virReportError(VIR_ERR_NO_SUPPORT,
                        "%s", _("storage pool does not support"
-- 
1.8.3.1

-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India