Skip to content

Remove overlayfs volatile option on temp mounts #9555

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
estesp merged 1 commit into from
Jan 20, 2024
Merged

Remove overlayfs volatile option on temp mounts #9555

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
111 changes: 111 additions & 0 deletions core/mount/mount_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -148,3 +148,114 @@ func TestReadonlyMounts(t *testing.T) {
}
}
}

func TestRemoveVolatileTempMount(t *testing.T) {
testCases := []struct {
desc string
input []Mount
expected []Mount
}{
{
desc: "remove volatile option from overlay mounts, ignore non overlay",
input: []Mount{
{
Type: "overlay",
Source: "overlay",
Options: []string{
"index=off",
"workdir=/path/to/snapshots/4/work",
"upperdir=/path/to/snapshots/4/fs",
"lowerdir=/path/to/snapshots/1/fs",
"volatile",
},
},
{
Type: "underlay",
Source: "underlay",
Options: []string{
"index=on",
"lowerdir=/another/path/to/snapshots/2/fs",
"volatile",
},
},
},
expected: []Mount{
{
Type: "overlay",
Source: "overlay",
Options: []string{
"index=off",
"workdir=/path/to/snapshots/4/work",
"upperdir=/path/to/snapshots/4/fs",
"lowerdir=/path/to/snapshots/1/fs",
},
},
{
Type: "underlay",
Source: "underlay",
Options: []string{
"index=on",
"lowerdir=/another/path/to/snapshots/2/fs",
"volatile",
},
},
},
},
{
desc: "return original slice since no volatile options on overlay",
input: []Mount{
{
Type: "overlay",
Source: "overlay",
Options: []string{
"index=off",
"workdir=/path/to/snapshots/4/work",
"upperdir=/path/to/snapshots/4/fs",
"lowerdir=/path/to/snapshots/1/fs",
},
},
{
Type: "underlay",
Source: "underlay",
Options: []string{
"index=on",
"lowerdir=/another/path/to/snapshots/2/fs",
"volatile",
},
},
},
expected: []Mount{
{
Type: "overlay",
Source: "overlay",
Options: []string{
"index=off",
"workdir=/path/to/snapshots/4/work",
"upperdir=/path/to/snapshots/4/fs",
"lowerdir=/path/to/snapshots/1/fs",
},
},
{
Type: "underlay",
Source: "underlay",
Options: []string{
"index=on",
"lowerdir=/another/path/to/snapshots/2/fs",
"volatile",
},
},
},
},
}

for _, tc := range testCases {
original := copyMounts(tc.input)
actual := removeVolatileTempMount(tc.input)
if !reflect.DeepEqual(actual, tc.expected) {
t.Fatalf("incorrectly modified mounts: %s.\n\n Expected: %v\n\n, Actual: %v", tc.desc, tc.expected, actual)
}
if !reflect.DeepEqual(original, tc.input) {
t.Fatalf("modified original mounts: %s.\n\n Expected: %v\n\n, Actual: %v", tc.desc, original, tc.input)
}
}
}
40 changes: 39 additions & 1 deletion core/mount/temp.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@ var tempMountLocation = getTempDir()

// WithTempMount mounts the provided mounts to a temp dir, and pass the temp dir to f.
// The mounts are valid during the call to the f.
// The volatile option of overlayfs doesn't allow to mount again using the same upper / work dirs. Since it's a temp mount, avoid using that option here if found.
// Finally we will unmount and remove the temp dir regardless of the result of f.
func WithTempMount(ctx context.Context, mounts []Mount, f func(root string) error) (err error) {
root, uerr := os.MkdirTemp(tempMountLocation, "containerd-mount")
Expand Down Expand Up @@ -58,7 +59,8 @@ func WithTempMount(ctx context.Context, mounts []Mount, f func(root string) erro
}
}
}()
if uerr = All(mounts, root); uerr != nil {

if uerr = All(removeVolatileTempMount(mounts), root); uerr != nil {
return fmt.Errorf("failed to mount %s: %w", root, uerr)
}
if err := f(root); err != nil {
Expand All @@ -67,6 +69,42 @@ func WithTempMount(ctx context.Context, mounts []Mount, f func(root string) erro
return nil
}

// removeVolatileTempMount The volatile option of overlayfs doesn't allow to mount again using the
// same upper / work dirs. Since it's a temp mount, avoid using that
// option here. Reference: https://docs.kernel.org/filesystems/overlayfs.html#volatile-mount
// TODO: Make this logic conditional once the kernel supports reusing
// overlayfs volatile mounts.
func removeVolatileTempMount(mounts []Mount) []Mount {
var out []Mount
for i, m := range mounts {
if m.Type != "overlay" {
continue
}
for j, opt := range m.Options {
if opt == "volatile" {
Comment thread
KodieGlosserIBM marked this conversation as resolved.
if out == nil {
out = copyMounts(mounts)
}
out[i].Options = append(out[i].Options[:j], out[i].Options[j+1:]...)
break
}
}
}

if out != nil {
return out
}

return mounts
}

// copyMounts creates a copy of the original slice to allow for modification and not altering the original
func copyMounts(in []Mount) []Mount {
out := make([]Mount, len(in))
copy(out, in)
return out
}

// WithReadonlyTempMount mounts the provided mounts to a temp dir as readonly,
// and pass the temp dir to f. The mounts are valid during the call to the f.
// Finally we will unmount and remove the temp dir regardless of the result of f.
Expand Down