[libvirt] [PATCH] qemu: Adjust size for qcow2/qed if not on sector boundary (rewrite)

[John Ferlan]

A post commit id 'e3d66229' review (and followup):

http://www.redhat.com/archives/libvir-list/2014-May/msg00268.html

noted some issues with the code, so I have adjusted the code
accordingly. The difference between this and the commit prior
to the change (commit id 'f3be5f0c') will just be the check for
qcow2/qed using a non 512 block aligned size will result in a
round up of size. If the size is within the last 512 bytes to
ULLONG_MAX, then just set it there rather than erroring out.

Signed-off-by: John Ferlan <jferlan at redhat.com>
---
 src/qemu/qemu_driver.c | 28 +++++++++-------------------
 1 file changed, 9 insertions(+), 19 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 4ff8a2d..8771cae 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -9413,7 +9413,6 @@ qemuDomainBlockResize(virDomainPtr dom,
     virDomainObjPtr vm;
     qemuDomainObjPrivatePtr priv;
     int ret = -1, idx;
-    unsigned long long size_up;
     char *device = NULL;
     virDomainDiskDefPtr disk = NULL;
 
@@ -9434,12 +9433,6 @@ qemuDomainBlockResize(virDomainPtr dom,
             return -1;
         }
         size *= 1024;
-        size_up = size;
-    } else {
-        /* For 'qcow2' and 'qed', qemu resize blocks expects values
-         * on sector boundary, so round our value up to prepare
-         */
-        size_up = VIR_ROUND_UP(size, 512);
     }
 
     if (!(vm = qemuDomObjFromDomain(dom)))
@@ -9466,19 +9459,16 @@ qemuDomainBlockResize(virDomainPtr dom,
     }
     disk = vm->def->disks[idx];
 
-    /* qcow2 and qed must be sized appropriately, so be sure our value
-     * is sized appropriately and will fit
+    /* qcow2 and qed must be sized on 512 byte blocks/sectors,
+     * so adjust size if necessary to round up (if possible).
      */
-    if (size != size_up &&
-        (disk->src.format == VIR_STORAGE_FILE_QCOW2 ||
-         disk->src.format == VIR_STORAGE_FILE_QED)) {
-        if (size_up > ULLONG_MAX) {
-            virReportError(VIR_ERR_OVERFLOW,
-                           _("size must be less than %llu KiB"),
-                           ULLONG_MAX / 1024);
-            goto endjob;
-        }
-        size = size_up;
+    if ((disk->src.format == VIR_STORAGE_FILE_QCOW2 ||
+         disk->src.format == VIR_STORAGE_FILE_QED) &&
+        (size % 512)) {
+        if ((ULLONG_MAX - size) < 512)
+            size = ULLONG_MAX;
+        else
+            size = VIR_ROUND_UP(size, 512);
     }
 
     if (virAsprintf(&device, "%s%s", QEMU_DRIVE_HOST_PREFIX,
-- 
1.9.0