lxd/storage/drivers: Refactor volume size rounding logic

Signed-off-by: Wesley Hershberger <wesley.hershberger@canonical.com>

lxd/storage/drivers/driver_common.go

@@ -549,23 +549,12 @@ func (d *common) DeleteBucketKey(bucket Volume, keyName string, op *operations.O
 	return nil
 }
 
-// roundVolumeBlockSizeBytes returns size rounded to the nearest multiple of MinBlockBoundary bytes that is equal
-// to or larger than sizeBytes.
+// roundVolumeBlockSizeBytes returns sizeBytes rounded up to the next multiple
+// of MinBlockBoundary.
 func (d *common) roundVolumeBlockSizeBytes(vol Volume, sizeBytes int64) int64 {
 	// QEMU requires image files to be in traditional storage block boundaries.
 	// We use 8k here to ensure our images are compatible with all of our backend drivers.
-	if sizeBytes < MinBlockBoundary {
-		sizeBytes = MinBlockBoundary
-	}
-
-	roundedSizeBytes := int64(sizeBytes/MinBlockBoundary) * MinBlockBoundary
-
-	// Ensure the rounded size is at least the size specified in sizeBytes.
-	if roundedSizeBytes < sizeBytes {
-		roundedSizeBytes += MinBlockBoundary
-	}
-
-	return roundedSizeBytes
+	return roundAbove(MinBlockBoundary, sizeBytes)
 }
 
 func (d *common) isBlockBacked(vol Volume) bool {

lxd/storage/drivers/driver_lvm.go

@@ -782,21 +782,10 @@ func (d *lvm) GetResources() (*api.ResourcesStoragePool, error) {
 	return &res, nil
 }
 
-// roundVolumeBlockSizeBytes returns size rounded to the nearest multiple of the volume group extent size that is
-// equal to or larger than sizeBytes.
+// roundVolumeBlockSizeBytes returns sizeBytes rounded up to the next multiple
+// of the volume group extent size.
 func (d *lvm) roundVolumeBlockSizeBytes(vol Volume, sizeBytes int64) int64 {
 	// Get the volume group's physical extent size, and use that as minimum size.
 	vgExtentSize, _ := d.volumeGroupExtentSize(d.config["lvm.vg_name"])
-	if sizeBytes < vgExtentSize {
-		sizeBytes = vgExtentSize
-	}
-
-	roundedSizeBytes := int64(sizeBytes/vgExtentSize) * vgExtentSize
-
-	// Ensure the rounded size is at least the size specified in sizeBytes.
-	if roundedSizeBytes < sizeBytes {
-		roundedSizeBytes += vgExtentSize
-	}
-
-	return roundedSizeBytes
+	return roundAbove(vgExtentSize, sizeBytes)
 }

lxd/storage/drivers/driver_zfs.go

@@ -755,16 +755,5 @@ func (d *zfs) roundVolumeBlockSizeBytes(vol Volume, sizeBytes int64) int64 {
 		minBlockSize = 16 * 1024
 	}
 
-	if sizeBytes < minBlockSize {
-		sizeBytes = minBlockSize
-	}
-
-	roundedSizeBytes := int64(sizeBytes/minBlockSize) * minBlockSize
-
-	// Ensure the rounded size is at least the size specified in sizeBytes.
-	if roundedSizeBytes < sizeBytes {
-		roundedSizeBytes += minBlockSize
-	}
-
-	return roundedSizeBytes
+	return roundAbove(minBlockSize, sizeBytes)
 }

lxd/storage/drivers/utils.go

@@ -876,3 +876,19 @@ func wipeBlockHeaders(path string) error {
 func IsContentBlock(contentType ContentType) bool {
 	return contentType == ContentTypeBlock || contentType == ContentTypeISO
 }
+
+// roundAbove returns the next multiple of `above` greater than `val`.
+func roundAbove(above, val int64) int64 {
+	if val < above {
+		val = above
+	}
+
+	rounded := int64(val/above) * above
+
+	// Ensure the rounded size is at least x.
+	if rounded < val {
+		rounded += above
+	}
+
+	return rounded
+}