qemu: Fix qemuDomainGetBlockInfo allocation value setting

https://bugzilla.redhat.com/show_bug.cgi?id=1467826

Commit id 'b9b1aa639' was supposed to add logic to set the allocation
for sparse files when wr_highest_offset was zero; however, an unconditional
setting was done just prior. For block devices, this means allocation is
always returning 0 since 'actual-size' will be zero.

Remove the unconditional setting and add the note about it being possible
to still be zero for block devices. As soon as the guest starts writing to
the volume, the allocation value will then be obtainable from qemu via
the wr_highest_offset.

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index a7019c53ccdcc7a7d911dfc80eb8db6a60ba575b..8d261b7257ef06c02c61369031728bd702df14e5 100644 (file)
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -11708,10 +11708,9 @@ qemuDomainGetBlockInfo(virDomainPtr dom,
      * Additionally, if qemu hasn't written to the file yet, then set the
      * allocation to whatever qemu returned for physical (e.g. the "actual-
      * size" from the json query) as that will match the expected allocation
-     * value for this API. */
+     * value for this API. NB: May still be 0 for block. */
     if (entry->physical == 0 || info->allocation == 0 ||
         info->allocation == entry->physical) {
-        info->allocation = entry->physical;
         if (info->allocation == 0)
             info->allocation = entry->physical;