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Merge pull request #35527 from thaJeztah/feature-detect-overlay2

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Detect overlay2 support on pre-4.0 kernels
This commit is contained in:
Victor Vieux 2017-11-29 13:51:26 -08:00 • committed by GitHub
commit 11e07e7da6
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 45 additions and 10 deletions
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32
daemon/graphdriver/overlay2/check.go
View file

@ -100,3 +100,35 @@ func doesSupportNativeDiff(d string) error {
return nil
}
// supportsMultipleLowerDir checks if the system supports multiple lowerdirs,
// which is required for the overlay2 driver. On 4.x kernels, multiple lowerdirs
// are always available (so this check isn't needed), and backported to RHEL and
// CentOS 3.x kernels (3.10.0-693.el7.x86_64 and up). This function is to detect
// support on those kernels, without doing a kernel version compare.
func supportsMultipleLowerDir(d string) error {
td, err := ioutil.TempDir(d, "multiple-lowerdir-check")
if err != nil {
return err
}
defer func() {
if err := os.RemoveAll(td); err != nil {
logrus.Warnf("Failed to remove check directory %v: %v", td, err)
}
}()
for _, dir := range []string{"lower1", "lower2", "upper", "work", "merged"} {
if err := os.Mkdir(filepath.Join(td, dir), 0755); err != nil {
return err
}
}
opts := fmt.Sprintf("lowerdir=%s:%s,upperdir=%s,workdir=%s", path.Join(td, "lower2"), path.Join(td, "lower1"), path.Join(td, "upper"), path.Join(td, "work"))
if err := unix.Mount("overlay", filepath.Join(td, "merged"), "overlay", 0, opts); err != nil {
return errors.Wrap(err, "failed to mount overlay")
}
if err := unix.Unmount(filepath.Join(td, "merged"), 0); err != nil {
logrus.Warnf("Failed to unmount check directory %v: %v", filepath.Join(td, "merged"), err)
}
return nil
}

23
daemon/graphdriver/overlay2/overlay.go
View file

@ -16,8 +16,6 @@ import (
"strings"
"sync"
"github.com/sirupsen/logrus"
"github.com/docker/docker/daemon/graphdriver"
"github.com/docker/docker/daemon/graphdriver/overlayutils"
"github.com/docker/docker/daemon/graphdriver/quota"
@ -32,9 +30,9 @@ import (
"github.com/docker/docker/pkg/parsers"
"github.com/docker/docker/pkg/parsers/kernel"
"github.com/docker/docker/pkg/system"
units "github.com/docker/go-units"
"github.com/docker/go-units"
"github.com/opencontainers/selinux/go-selinux/label"
"github.com/sirupsen/logrus"
"golang.org/x/sys/unix"
)
@ -137,12 +135,6 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
if err != nil {
return nil, err
}
if kernel.CompareKernelVersion(*v, kernel.VersionInfo{Kernel: 4, Major: 0, Minor: 0}) < 0 {
if !opts.overrideKernelCheck {
return nil, graphdriver.ErrNotSupported
}
logrus.Warn("Using pre-4.0.0 kernel for overlay2, mount failures may require kernel update")
}
fsMagic, err := graphdriver.GetFSMagic(home)
if err != nil {
@ -169,6 +161,17 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
}
}
if kernel.CompareKernelVersion(*v, kernel.VersionInfo{Kernel: 4, Major: 0, Minor: 0}) < 0 {
if opts.overrideKernelCheck {
logrus.Warn("Using pre-4.0.0 kernel for overlay2, mount failures may require kernel update")
} else {
if err := supportsMultipleLowerDir(filepath.Dir(home)); err != nil {
logrus.Debugf("Multiple lower dirs not supported: %v", err)
return nil, graphdriver.ErrNotSupported
}
}
}
rootUID, rootGID, err := idtools.GetRootUIDGID(uidMaps, gidMaps)
if err != nil {
return nil, err