[lxc-devel] [lxd/master] lxd/storage: Support deleting snapshots during restore

[stgraber on Github]

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From 993886156574bdf1bb62530acc6bddbf3bb925ed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber at ubuntu.com>
Date: Wed, 8 Jan 2020 15:57:05 -0500
Subject: [PATCH] lxd/storage: Support deleting snapshots during restore
MIME-Version: 1.0
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Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>
---
 lxd/storage/backend_lxd.go    | 60 ++++++++++++++++++++++++++++++++++-
 lxd/storage/drivers/errors.go |  9 ++++++
 2 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/lxd/storage/backend_lxd.go b/lxd/storage/backend_lxd.go
index 89f6882817..1ec8fc2025 100644
--- a/lxd/storage/backend_lxd.go
+++ b/lxd/storage/backend_lxd.go
@@ -1699,6 +1699,35 @@ func (b *lxdBackend) RestoreInstanceSnapshot(inst instance.Instance, src instanc
 	vol := b.newVolume(volType, contentType, volStorageName, rootDiskConf)
 	err = b.driver.RestoreVolume(vol, snapshotName, op)
 	if err != nil {
+		snapErr, ok := err.(drivers.ErrDeleteSnapshots)
+		if ok {
+			// We need to delete some snapshots and try again.
+			snaps, err := inst.Snapshots()
+			if err != nil {
+				return err
+			}
+
+			// Go through all the snapshots.
+			for _, snap := range snaps {
+				_, snapName, _ := shared.InstanceGetParentAndSnapshotName(src.Name())
+				if !shared.StringInSlice(snapName, snapErr.Snapshots) {
+					continue
+				}
+
+				// Delete if listed.
+				err := b.DeleteInstanceSnapshot(snap, op)
+				if err != nil {
+					return err
+				}
+			}
+
+			// Now try again.
+			err = b.driver.RestoreVolume(vol, snapshotName, op)
+			if err != nil {
+				return err
+			}
+		}
+
 		return err
 	}
 
@@ -2607,6 +2636,7 @@ func (b *lxdBackend) RestoreCustomVolume(volName string, snapshotName string, op
 	logger.Debug("RestoreCustomVolume started")
 	defer logger.Debug("RestoreCustomVolume finished")
 
+	// Sanity checks.
 	if shared.IsSnapshot(volName) {
 		return fmt.Errorf("Volume cannot be snapshot")
 	}
@@ -2615,6 +2645,7 @@ func (b *lxdBackend) RestoreCustomVolume(volName string, snapshotName string, op
 		return fmt.Errorf("Invalid snapshot name")
 	}
 
+	// Check that the volume isn't in use.
 	usingVolume, err := VolumeUsedByInstancesWithProfiles(b.state, b.Name(), volName, db.StoragePoolVolumeTypeNameCustom, true)
 	if err != nil {
 		return err
@@ -2624,8 +2655,35 @@ func (b *lxdBackend) RestoreCustomVolume(volName string, snapshotName string, op
 		return fmt.Errorf("Cannot restore custom volume used by running instances")
 	}
 
-	err = b.driver.RestoreVolume(b.newVolume(drivers.VolumeTypeCustom, drivers.ContentTypeFS, volName, nil), snapshotName, op)
+	// Get the volume config.
+	_, dbVol, err := b.state.Cluster.StoragePoolNodeVolumeGetTypeByProject("default", volName, db.StoragePoolVolumeTypeCustom, b.ID())
+	if err != nil {
+		if err == db.ErrNoSuchObject {
+			return fmt.Errorf("Volume doesn't exist")
+		}
+
+		return err
+	}
+
+	err = b.driver.RestoreVolume(b.newVolume(drivers.VolumeTypeCustom, drivers.ContentTypeFS, volName, dbVol.Config), snapshotName, op)
 	if err != nil {
+		snapErr, ok := err.(drivers.ErrDeleteSnapshots)
+		if ok {
+			// We need to delete some snapshots and try again.
+			for _, snapName := range snapErr.Snapshots {
+				err := b.DeleteCustomVolumeSnapshot(fmt.Sprintf("%s/%s", volName, snapName), op)
+				if err != nil {
+					return err
+				}
+			}
+
+			// Now try again.
+			err = b.driver.RestoreVolume(b.newVolume(drivers.VolumeTypeCustom, drivers.ContentTypeFS, volName, dbVol.Config), snapshotName, op)
+			if err != nil {
+				return err
+			}
+		}
+
 		return err
 	}
 
diff --git a/lxd/storage/drivers/errors.go b/lxd/storage/drivers/errors.go
index e9fb157bc6..cae5eba16a 100644
--- a/lxd/storage/drivers/errors.go
+++ b/lxd/storage/drivers/errors.go
@@ -12,3 +12,12 @@ var ErrUnknownDriver = fmt.Errorf("Unknown driver")
 
 // ErrNotSupported is the "Not supported" error
 var ErrNotSupported = fmt.Errorf("Not supported")
+
+// ErrDeleteSnapshots is a special error used to tell the backend to delete more recent snapshots
+type ErrDeleteSnapshots struct {
+	Snapshots []string
+}
+
+func (e ErrDeleteSnapshots) Error() string {
+	return fmt.Sprintf("More recent snapshots must be deleted: %+v", e.Snapshots)
+}