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check if snapshot holds mountpoint before remove #302

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Sep 12, 2024
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30 changes: 30 additions & 0 deletions internal/log/helper.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
/*
Copyright The Accelerated Container Image Authors

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package log

import (
"context"
"fmt"

clog "github.com/containerd/log"
)

func TracedErrorf(ctx context.Context, format string, args ...any) error {
err := fmt.Errorf(format, args...)
clog.G(ctx).Error(err)
return err
}
13 changes: 11 additions & 2 deletions pkg/snapshot/overlay.go
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@ import (
"github.com/containerd/accelerated-container-image/pkg/label"
"github.com/containerd/accelerated-container-image/pkg/snapshot/diskquota"

mylog "github.com/containerd/accelerated-container-image/internal/log"
"github.com/containerd/accelerated-container-image/pkg/metrics"
"github.com/data-accelerator/zdfs"
"github.com/sirupsen/logrus"
Expand Down Expand Up @@ -944,7 +945,7 @@ func (o *snapshotter) Remove(ctx context.Context, key string) (err error) {
if err == nil {
err = o.unmountAndDetachBlockDevice(ctx, id, key)
if err != nil {
return errors.Wrapf(err, "failed to destroy target device for snapshot %s", key)
return mylog.TracedErrorf(ctx, "failed to destroy target device for snapshot %s: %w", key, err)
}
}
}
Expand All @@ -961,12 +962,20 @@ func (o *snapshotter) Remove(ctx context.Context, key string) (err error) {
if st, err := o.identifySnapshotStorageType(ctx, s.ParentIDs[0], info); err == nil && st != storageTypeNormal {
err = o.unmountAndDetachBlockDevice(ctx, s.ParentIDs[0], "")
if err != nil {
return errors.Wrapf(err, "failed to destroy target device for snapshot %s", key)
return mylog.TracedErrorf(ctx, "failed to destroy target device for snapshot %s: %w", key, err)
}
}
}
}

// Just in case, check if snapshot contains mountpoint
mounted, err := o.isMounted(ctx, o.overlaybdMountpoint(id))
if err != nil {
return mylog.TracedErrorf(ctx, "failed to check mountpoint: %w", err)
} else if mounted {
return mylog.TracedErrorf(ctx, "try to remove snapshot %s which still have mountpoint", id)
}

_, _, err = storage.Remove(ctx, key)
if err != nil {
return errors.Wrap(err, "failed to remove")
Expand Down
40 changes: 29 additions & 11 deletions pkg/snapshot/storage.go
Original file line number Diff line number Diff line change
Expand Up @@ -68,21 +68,45 @@ const (
obdMaxDataAreaMB = 4
)

type mountMatcherFunc func(fields []string, separatorIndex int) bool

func (o *snapshotter) checkOverlaybdInUse(ctx context.Context, dir string) (bool, error) {
matcher := func(fields []string, separatorIndex int) bool {
// ... but in Linux <= 3.9 mounting a cifs with spaces in a share name
// (like "//serv/My Documents") _may_ end up having a space in the last field
// of mountinfo (like "unc=//serv/My Documents"). Since kernel 3.10-rc1, cifs
// option unc= is ignored, so a space should not appear. In here we ignore
// those "extra" fields caused by extra spaces.
fstype := fields[separatorIndex+1]
vfsOpts := fields[separatorIndex+3]
return fstype == "overlay" && strings.Contains(vfsOpts, dir)
}
return o.matchMounts(ctx, matcher)
}

func (o *snapshotter) isMounted(ctx context.Context, mountpoint string) (bool, error) {
matcher := func(fields []string, separatorIndex int) bool {
mp := fields[4]
return path.Clean(mountpoint) == path.Clean(mp)
}
return o.matchMounts(ctx, matcher)
}

func (o *snapshotter) matchMounts(ctx context.Context, matcher mountMatcherFunc) (bool, error) {
f, err := os.Open("/proc/self/mountinfo")
if err != nil {
return false, err
}
defer f.Close()
b, err := o.parseAndCheckMounted(ctx, f, dir)
b, err := o.parseAndCheckMounted(ctx, f, matcher)
if err != nil {
log.G(ctx).Errorf("Parsing mounts fields, error: %v", err)
return false, err
}
return b, nil
}

func (o *snapshotter) parseAndCheckMounted(ctx context.Context, r io.Reader, dir string) (bool, error) {
func (o *snapshotter) parseAndCheckMounted(ctx context.Context, r io.Reader, matcher mountMatcherFunc) (bool, error) {
s := bufio.NewScanner(r)
for s.Scan() {
if err := s.Err(); err != nil {
Expand Down Expand Up @@ -139,21 +163,15 @@ func (o *snapshotter) parseAndCheckMounted(ctx context.Context, r io.Reader, dir
log.G(ctx).Warnf("Parsing '%s' failed: not enough fields after a separator", text)
continue
}
// ... but in Linux <= 3.9 mounting a cifs with spaces in a share name
// (like "//serv/My Documents") _may_ end up having a space in the last field
// of mountinfo (like "unc=//serv/My Documents"). Since kernel 3.10-rc1, cifs
// option unc= is ignored, so a space should not appear. In here we ignore
// those "extra" fields caused by extra spaces.
fstype := fields[i+1]
vfsOpts := fields[i+3]
if fstype == "overlay" && strings.Contains(vfsOpts, dir) {

if matcher(fields, i) {
return true, nil
}
}
return false, nil
}

// unmountAndDetachBlockDevice
// unmountAndDetachBlockDevice will do nothing if the device is already destroyed
func (o *snapshotter) unmountAndDetachBlockDevice(ctx context.Context, snID string, snKey string) (err error) {
devName, err := os.ReadFile(o.overlaybdBackstoreMarkFile(snID))
if err != nil {
Expand Down
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