[lxc-devel] [lxd/master] VM: Block boundary size

[tomponline on Github]

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From db666fd8e07472af79afdbdb1be4f0cd329a1b2c Mon Sep 17 00:00:00 2001
From: Thomas Parrott <thomas.parrott at canonical.com>
Date: Mon, 20 Jan 2020 09:09:46 +0000
Subject: [PATCH 1/2] lxd/storage/drivers/utils: Updates ensureVolumeBlockFile
 to use minimum block boundary size of 8192 bytes

To avoid qemu issues when VM volume size is specified in metric sizes.

Signed-off-by: Thomas Parrott <thomas.parrott at canonical.com>
---
 lxd/storage/drivers/utils.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lxd/storage/drivers/utils.go b/lxd/storage/drivers/utils.go
index 0cc9aed225..9d69e3b0e2 100644
--- a/lxd/storage/drivers/utils.go
+++ b/lxd/storage/drivers/utils.go
@@ -301,6 +301,16 @@ func ensureVolumeBlockFile(vol Volume, path string) error {
 		return err
 	}
 
+	// Qemu requires image files to be in traditial 1k, 4k or 8k block boundaries.
+	// We use 8k here to ensure our images are compatible with all of our backend drivers.
+	const minBlockBoundary = 8192
+	if blockSizeBytes < minBlockBoundary {
+		blockSizeBytes = minBlockBoundary
+	}
+
+	// Round the size to closest minBlockBoundary bytes to avoid qemu boundary issues.
+	blockSizeBytes = int64(blockSizeBytes/minBlockBoundary) * minBlockBoundary
+
 	if shared.PathExists(path) {
 		_, err = shared.RunCommand("qemu-img", "resize", "-f", "raw", path, fmt.Sprintf("%d", blockSizeBytes))
 		if err != nil {

From 240ffe16c7e0f5752765b4352091b519ecca71b0 Mon Sep 17 00:00:00 2001
From: Thomas Parrott <thomas.parrott at canonical.com>
Date: Mon, 20 Jan 2020 09:16:26 +0000
Subject: [PATCH 2/2] lxd/storage/drivers/driver/lvm/utils: Avoid repetition of
 512 bytes in roundedSizeBytesString

Signed-off-by: Thomas Parrott <thomas.parrott at canonical.com>
---
 lxd/storage/drivers/driver_lvm_utils.go | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/lxd/storage/drivers/driver_lvm_utils.go b/lxd/storage/drivers/driver_lvm_utils.go
index 77f717f31b..ea1999c18a 100644
--- a/lxd/storage/drivers/driver_lvm_utils.go
+++ b/lxd/storage/drivers/driver_lvm_utils.go
@@ -316,12 +316,14 @@ func (d *lvm) roundedSizeBytesString(size string) (int64, error) {
 		return 0, err
 	}
 
-	if sizeBytes < 512 {
-		sizeBytes = 512
+	// LVM tools require sizes in multiples of 512 bytes.
+	const minSizeBytes = 512
+	if sizeBytes < minSizeBytes {
+		sizeBytes = minSizeBytes
 	}
 
-	// Round the size to closest 512 bytes as LVM tools require sizes in multiples of 512 bytes.
-	sizeBytes = int64(sizeBytes/512) * 512
+	// Round the size to closest minSizeBytes bytes.
+	sizeBytes = int64(sizeBytes/minSizeBytes) * minSizeBytes
 
 	return sizeBytes, nil
 }