diff --git a/drivers/overlay/check.go b/drivers/overlay/check.go index 60980994b2..d8139f6566 100644 --- a/drivers/overlay/check.go +++ b/drivers/overlay/check.go @@ -275,3 +275,36 @@ func supportsIdmappedLowerLayers(home string) (bool, error) { }() return true, nil } + +// supportsDataOnlyLayers checks if the kernel supports mounting a overlay file system +// that uses data-only layers. +func supportsDataOnlyLayers(home string) (bool, error) { + layerDir, err := os.MkdirTemp(home, "compat") + if err != nil { + return false, err + } + defer func() { + _ = os.RemoveAll(layerDir) + }() + + mergedDir := filepath.Join(layerDir, "merged") + lowerDir := filepath.Join(layerDir, "lower") + lowerDirDataOnly := filepath.Join(layerDir, "lower-data") + upperDir := filepath.Join(layerDir, "upper") + workDir := filepath.Join(layerDir, "work") + + _ = idtools.MkdirAs(mergedDir, 0o700, 0, 0) + _ = idtools.MkdirAs(lowerDir, 0o700, 0, 0) + _ = idtools.MkdirAs(lowerDirDataOnly, 0o700, 0, 0) + _ = idtools.MkdirAs(upperDir, 0o700, 0, 0) + _ = idtools.MkdirAs(workDir, 0o700, 0, 0) + + opts := fmt.Sprintf("lowerdir=%s::%s,upperdir=%s,workdir=%s,metacopy=on", lowerDir, lowerDirDataOnly, upperDir, workDir) + flags := uintptr(0) + if err := unix.Mount("overlay", mergedDir, "overlay", flags, opts); err != nil { + return false, err + } + _ = unix.Unmount(mergedDir, unix.MNT_DETACH) + + return true, nil +} diff --git a/drivers/overlay/mount.go b/drivers/overlay/mount.go index 33e60b1189..bc052f33b4 100644 --- a/drivers/overlay/mount.go +++ b/drivers/overlay/mount.go @@ -141,14 +141,27 @@ func mountOverlayFromMain() { // the new value for the list of lowers, because it's shorter. if lowerv != "" { lowers := strings.Split(lowerv, ":") + var newLowers []string + dataOnly := false for i := range lowers { + if lowers[i] == "" { + dataOnly = true + continue + } lowerFd, err := unix.Open(lowers[i], unix.O_RDONLY, 0) if err != nil { fatal(err) } - lowers[i] = fmt.Sprintf("%d", lowerFd) + var lower string + if dataOnly { + lower = fmt.Sprintf(":%d", lowerFd) + dataOnly = false + } else { + lower = fmt.Sprintf("%d", lowerFd) + } + newLowers = append(newLowers, lower) } - lowerv = strings.Join(lowers, ":") + lowerv = strings.Join(newLowers, ":") } // Reconstruct the Label field. diff --git a/drivers/overlay/overlay.go b/drivers/overlay/overlay.go index 91ca273de0..568398bc7f 100644 --- a/drivers/overlay/overlay.go +++ b/drivers/overlay/overlay.go @@ -1657,8 +1657,6 @@ func (d *Driver) get(id string, disableShifting bool, options graphdriver.MountO optsList = append(optsList, "metacopy=on", "redirect_dir=on") } - absLowers = append(absLowers, composeFsLayers...) - if len(absLowers) == 0 { absLowers = append(absLowers, path.Join(dir, "empty")) } @@ -1752,11 +1750,20 @@ func (d *Driver) get(id string, disableShifting bool, options graphdriver.MountO absLowers = newAbsDir } + lowerDirs := strings.Join(absLowers, ":") + if len(composeFsLayers) > 0 { + composeFsLayersLowerDirs := strings.Join(composeFsLayers, "::") + lowerDirs = lowerDirs + "::" + composeFsLayersLowerDirs + } + // absLowers is not valid anymore now as we have added composeFsLayers to it, so prevent + // its usage. + absLowers = nil //nolint:ineffassign + var opts string if readWrite { - opts = fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", strings.Join(absLowers, ":"), diffDir, workdir) + opts = fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", lowerDirs, diffDir, workdir) } else { - opts = fmt.Sprintf("lowerdir=%s:%s", diffDir, strings.Join(absLowers, ":")) + opts = fmt.Sprintf("lowerdir=%s:%s", diffDir, lowerDirs) } if len(optsList) > 0 { opts = fmt.Sprintf("%s,%s", opts, strings.Join(optsList, ",")) @@ -1800,9 +1807,9 @@ func (d *Driver) get(id string, disableShifting bool, options graphdriver.MountO if readWrite { diffDir := path.Join(id, "diff") workDir := path.Join(id, "work") - opts = fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", strings.Join(absLowers, ":"), diffDir, workDir) + opts = fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", lowerDirs, diffDir, workDir) } else { - opts = fmt.Sprintf("lowerdir=%s:%s", diffDir, strings.Join(absLowers, ":")) + opts = fmt.Sprintf("lowerdir=%s:%s", diffDir, lowerDirs) } if len(optsList) > 0 { opts = strings.Join(append([]string{opts}, optsList...), ",") @@ -2009,11 +2016,34 @@ func (d *Driver) CleanupStagingDirectory(stagingDirectory string) error { return os.RemoveAll(stagingDirectory) } +func (d *Driver) supportsDataOnlyLayers() (bool, error) { + feature := "dataonly-layers" + overlayCacheResult, overlayCacheText, err := cachedFeatureCheck(d.runhome, feature) + if err == nil { + if overlayCacheResult { + logrus.Debugf("Cached value indicated that data-only layers for overlay are supported") + return true, nil + } + logrus.Debugf("Cached value indicated that data-only layers for overlay are not supported") + return false, errors.New(overlayCacheText) + } + supportsDataOnly, err := supportsDataOnlyLayers(d.home) + if err2 := cachedFeatureRecord(d.runhome, feature, supportsDataOnly, ""); err2 != nil { + return false, fmt.Errorf("recording overlay data-only layers support status: %w", err2) + } + return supportsDataOnly, err +} + func (d *Driver) useComposeFs() bool { if !composeFsSupported() || unshare.IsRootless() { return false } - return true + supportsDataOnlyLayers, err := d.supportsDataOnlyLayers() + if err != nil { + logrus.Debugf("Check for data-only layers failed with: %v", err) + return true + } + return supportsDataOnlyLayers } // ApplyDiff applies the changes in the new layer using the specified function