[lxc-devel] [lxd/master] Storage resize and UUID regeneration

[tomponline on Github]

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From 529a839a949a3cadd1d8c33e1909ba9729f3262b Mon Sep 17 00:00:00 2001
From: Thomas Parrott <thomas.parrott at canonical.com>
Date: Thu, 9 Jan 2020 12:03:00 +0000
Subject: [PATCH 1/3] lxd/storage/drivers/utils: Comment on shrinkFileSystem

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

diff --git a/lxd/storage/drivers/utils.go b/lxd/storage/drivers/utils.go
index 91c5e939e4..6797096f7f 100644
--- a/lxd/storage/drivers/utils.go
+++ b/lxd/storage/drivers/utils.go
@@ -406,6 +406,7 @@ func resolveMountOptions(options string) (uintptr, string) {
 
 // shrinkFileSystem shrinks a filesystem if it is supported. Ext4 volumes will be unmounted temporarily if needed.
 func shrinkFileSystem(fsType string, devPath string, vol Volume, byteSize int64) error {
+	// The smallest unit that resize2fs accepts in byte size (rather than blocks) is kilobytes.
 	strSize := fmt.Sprintf("%dK", byteSize/1024)
 
 	switch fsType {

From e1fbb4ca5156b23a8f288c3f5a922b2892528def Mon Sep 17 00:00:00 2001
From: Thomas Parrott <thomas.parrott at canonical.com>
Date: Thu, 9 Jan 2020 13:35:55 +0000
Subject: [PATCH 2/3] lxd/storage/drivers/utils: Mounts btrfs filesystems
 during shrinkFileSystem

This is required to resize the filesystem.

Signed-off-by: Thomas Parrott <thomas.parrott at canonical.com>
---
 lxd/storage/drivers/utils.go | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/lxd/storage/drivers/utils.go b/lxd/storage/drivers/utils.go
index 6797096f7f..32ecbcdf38 100644
--- a/lxd/storage/drivers/utils.go
+++ b/lxd/storage/drivers/utils.go
@@ -429,15 +429,17 @@ func shrinkFileSystem(fsType string, devPath string, vol Volume, byteSize int64)
 			return nil
 		}, nil)
 	case "btrfs":
-		_, err := shared.TryRunCommand("btrfs", "filesystem", "resize", strSize, vol.MountPath())
-		if err != nil {
-			return err
-		}
+		return vol.MountTask(func(mountPath string, op *operations.Operation) error {
+			_, err := shared.TryRunCommand("btrfs", "filesystem", "resize", strSize, mountPath)
+			if err != nil {
+				return err
+			}
+
+			return nil
+		}, nil)
 	default:
 		return fmt.Errorf(`Shrinking not supported for filesystem type "%s"`, fsType)
 	}
-
-	return nil
 }
 
 // growFileSystem grows a filesystem if it is supported. The volume will be mounted temporarily if needed.

From 860e2383bbacffa30d5e8f8c4f14943c6c3f6add Mon Sep 17 00:00:00 2001
From: Thomas Parrott <thomas.parrott at canonical.com>
Date: Thu, 9 Jan 2020 15:05:08 +0000
Subject: [PATCH 3/3] lxd/storage/drivers/utils: Adds regenerateFilesystemUUID
 functions

Signed-off-by: Thomas Parrott <thomas.parrott at canonical.com>
---
 lxd/storage/drivers/utils.go | 48 ++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/lxd/storage/drivers/utils.go b/lxd/storage/drivers/utils.go
index 32ecbcdf38..19a877d1c1 100644
--- a/lxd/storage/drivers/utils.go
+++ b/lxd/storage/drivers/utils.go
@@ -468,3 +468,51 @@ func growFileSystem(fsType string, devPath string, vol Volume) error {
 		return nil
 	}, nil)
 }
+
+// regenerateFilesystemUUID changes the filesystem UUID to a new randomly generated one if the fsType requires it.
+// Otherwise this function does nothing.
+func regenerateFilesystemUUID(fsType, devPath string) error {
+	switch fsType {
+	case "btrfs":
+		return regenerateFilesystemBTRFSUUID(devPath)
+	case "xfs":
+		return regenerateFilesystemXFSUUID(devPath)
+	}
+
+	return nil
+}
+
+// regenerateFilesystemBTRFSUUID changes the BTRFS filesystem UUID to a new randomly generated one.
+func regenerateFilesystemBTRFSUUID(devPath string) error {
+	_, err := shared.RunCommand("btrfstune", "-f", "-u", devPath)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// regenerateFilesystemXFSUUID changes the XFS filesystem UUID to a new randomly generated one.
+func regenerateFilesystemXFSUUID(devPath string) error {
+	// Attempt to generate a new UUID.
+	msg, err := shared.RunCommand("xfs_admin", "-U", "generate", devPath)
+	if err != nil {
+		return err
+	}
+
+	if msg != "" {
+		// Exit 0 with a msg usually means some log entry getting in the way.
+		_, err = shared.RunCommand("xfs_repair", "-o", "force_geometry", "-L", devPath)
+		if err != nil {
+			return err
+		}
+
+		// Attempt to generate a new UUID again.
+		_, err = shared.RunCommand("xfs_admin", "-U", "generate", devPath)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}