Check available disk space before creating an automatic snapshot on s…

…nap remove.

dirs/dirs.go

@@ -213,6 +213,11 @@ func isInsideBaseSnap() (bool, error) {
 	return err == nil, err
 }
 
+// SnapdStateDir returns the path to /var/lib/snapd dir under rootdir.
+func SnapdStateDir(rootdir string) string {
+	return filepath.Join(rootdir, snappyDir)
+}
+
 // SnapBlobDirUnder returns the path to the snap blob dir under rootdir.
 func SnapBlobDirUnder(rootdir string) string {
 	return filepath.Join(rootdir, snappyDir, "snaps")

overlord/snapstate/export_test.go

@@ -78,6 +78,12 @@ func MockOsutilEnsureUserGroup(mock func(name string, id uint32, extraUsers bool
 	return func() { osutilEnsureUserGroup = old }
 }
 
+func MockOsutilCheckFreeSpace(mock func(path string, minSize uint64) error) (restore func()) {
+	old := osutilCheckFreeSpace
+	osutilCheckFreeSpace = mock
+	return func() { osutilCheckFreeSpace = old }
+}
+
 var (
 	CoreInfoInternal       = coreInfo
 	CheckSnap              = checkSnap

overlord/snapstate/handlers_prereq_test.go

@@ -57,6 +57,9 @@ func (s *prereqSuite) SetUpTest(c *C) {
 	s.state.Set("seeded", true)
 	s.state.Set("refresh-privacy-key", "privacy-key")
 	s.AddCleanup(snapstatetest.MockDeviceModel(DefaultModel()))
+
+	restoreCheckFreeSpace := snapstate.MockOsutilCheckFreeSpace(func(string, uint64) error { return nil })
+	s.AddCleanup(restoreCheckFreeSpace)
 }
 
 func (s *prereqSuite) TestDoPrereqNothingToDo(c *C) {

overlord/snapstate/snapstate.go

@@ -37,6 +37,7 @@ import (
 	"github.com/snapcore/snapd/i18n"
 	"github.com/snapcore/snapd/interfaces"
 	"github.com/snapcore/snapd/logger"
+	"github.com/snapcore/snapd/osutil"
 	"github.com/snapcore/snapd/overlord/auth"
 	"github.com/snapcore/snapd/overlord/configstate/config"
 	"github.com/snapcore/snapd/overlord/ifacestate/ifacerepo"
@@ -70,6 +71,8 @@ const (
 
 var ErrNothingToDo = errors.New("nothing to do")
 
+var osutilCheckFreeSpace = osutil.CheckFreeSpace
+
 func isParallelInstallable(snapsup *SnapSetup) error {
 	if snapsup.InstanceKey == "" {
 		return nil
@@ -80,6 +83,11 @@ func isParallelInstallable(snapsup *SnapSetup) error {
 	return fmt.Errorf("cannot install snap of type %v as %q", snapsup.Type, snapsup.InstanceName())
 }
 
+func requiredSpaceWithMargin(minSize uint64) uint64 {
+	// 10% extra + 1Mb
+	return minSize + uint64(0.1 * float64(minSize)) + 1024*1024
+}
+
 func optedIntoSnapdSnap(st *state.State) (bool, error) {
 	tr := config.NewTransaction(st)
 	experimentalAllowSnapd, err := features.Flag(tr, features.SnapdSnap)
@@ -1909,6 +1917,16 @@ func Remove(st *state.State, name string, revision snap.Revision, flags *RemoveF
 		if tp, _ := snapst.Type(); tp == snap.TypeApp && removeAll {
 			ts, err := AutomaticSnapshot(st, name)
 			if err == nil {
+				if sz, err := EstimateSnapshotSize(st, name); err == nil {
+					requiredSpace := requiredSpaceWithMargin(uint64(sz))
+					if err := osutilCheckFreeSpace(dirs.SnapdStateDir(dirs.GlobalRootDir), requiredSpace); err != nil {
+						if _, ok := err.(*osutil.NotEnoughDiskSpaceError); ok {
+							return nil, fmt.Errorf("cannot create automatic snapshot when removing last revision of the snap: %v", err)
+						}
+						return nil, err
+					}
+				} // XXX: should we fail if estimation fails?
+
 				addNext(ts)
 			} else {
 				if err != ErrNothingToDo {

overlord/snapstate/snapstate_test.go

@@ -36,6 +36,7 @@ import (
 	"gopkg.in/tomb.v2"
 
 	"github.com/snapcore/snapd/asserts"
+	"github.com/snapcore/snapd/osutil"
 	"github.com/snapcore/snapd/bootloader"
 	"github.com/snapcore/snapd/bootloader/bootloadertest"
 	"github.com/snapcore/snapd/dirs"
@@ -100,6 +101,9 @@ func (s *snapmgrTestSuite) SetUpTest(c *C) {
 
 	s.BaseTest.AddCleanup(snap.MockSanitizePlugsSlots(func(snapInfo *snap.Info) {}))
 
+	restoreCheckFreeSpace := snapstate.MockOsutilCheckFreeSpace(func(string, uint64) error { return nil })
+	s.AddCleanup(restoreCheckFreeSpace)
+
 	s.fakeBackend = &fakeSnappyBackend{}
 	s.fakeBackend.emptyContainer = emptyContainer(c)
 	s.fakeStore = &fakeStore{
@@ -161,6 +165,10 @@ func (s *snapmgrTestSuite) SetUpTest(c *C) {
 		return nil, nil, nil
 	}))
 
+	oldEstimateSnapshotSize := snapstate.EstimateSnapshotSize
+	snapstate.EstimateSnapshotSize = func(st *state.State, instanceName string) (uint64, error) {
+		return 1, nil
+	}
 	oldAutomaticSnapshot := snapstate.AutomaticSnapshot
 	snapstate.AutomaticSnapshot = func(st *state.State, instanceName string) (ts *state.TaskSet, err error) {
 		task := st.NewTask("save-snapshot", "...")
@@ -171,6 +179,7 @@ func (s *snapmgrTestSuite) SetUpTest(c *C) {
 	oldAutomaticSnapshotExpiration := snapstate.AutomaticSnapshotExpiration
 	snapstate.AutomaticSnapshotExpiration = func(st *state.State) (time.Duration, error) { return 1, nil }
 	s.BaseTest.AddCleanup(func() {
+		snapstate.EstimateSnapshotSize = oldEstimateSnapshotSize
 		snapstate.AutomaticSnapshot = oldAutomaticSnapshot
 		snapstate.AutomaticSnapshotExpiration = oldAutomaticSnapshotExpiration
 	})
@@ -1065,6 +1074,51 @@ func (s *snapmgrTestSuite) TestRemoveConflict(c *C) {
 	c.Assert(err, ErrorMatches, `snap "some-snap" has "remove" change in progress`)
 }
 
+func (s *snapmgrTestSuite) TestRemoveDiskSpaceForSnapshotError(c *C) {
+	s.state.Lock()
+	defer s.state.Unlock()
+
+	restore := snapstate.MockOsutilCheckFreeSpace(func(string, uint64) error { return &osutil.NotEnoughDiskSpaceError{} })
+	defer restore()
+
+	snapstate.Set(s.state, "some-snap", &snapstate.SnapState{
+		Active:   true,
+		Sequence: []*snap.SideInfo{{RealName: "some-snap", Revision: snap.R(11)}},
+		Current:  snap.R(11),
+		SnapType: "app",
+	})
+
+	_, err := snapstate.Remove(s.state, "some-snap", snap.R(0), nil)
+	c.Assert(err, ErrorMatches, `cannot create automatic snapshot when removing last revision of the snap: insufficient space.*`)
+}
+
+
+func (s *snapmgrTestSuite) TestRemoveDiskSpaceForSnapshotNotCheckedWhenSnapshotsDisabled(c *C) {
+	s.state.Lock()
+	defer s.state.Unlock()
+
+	restore := snapstate.MockOsutilCheckFreeSpace(func(string, uint64) error { return &osutil.NotEnoughDiskSpaceError{} })
+	defer restore()
+
+	var automaticSnapshotCalled bool
+	snapstate.AutomaticSnapshot = func(st *state.State, instanceName string) (ts *state.TaskSet, err error) {
+		automaticSnapshotCalled = true
+		// ErrNothingToDo is returned if automatic snapshots are disabled
+		return nil, snapstate.ErrNothingToDo
+	}
+
+	snapstate.Set(s.state, "some-snap", &snapstate.SnapState{
+		Active:   true,
+		Sequence: []*snap.SideInfo{{RealName: "some-snap", Revision: snap.R(11)}},
+		Current:  snap.R(11),
+		SnapType: "app",
+	})
+
+	_, err := snapstate.Remove(s.state, "some-snap", snap.R(0), nil)
+	c.Assert(err, IsNil)
+	c.Assert(automaticSnapshotCalled, Equals, true)
+}
+
 func (s *snapmgrTestSuite) TestDisableSnapDisabledServicesSaved(c *C) {
 	s.state.Lock()
 	defer s.state.Unlock()