mirror of
https://github.com/containerd/containerd.git
synced 2026-11-06 13:27:16 +00:00
Maksym Pavlenko
1e001e6dfe
The cache used to serve a hit by committing the layer during Prepare and returning ErrAlreadyExists, which is incompatible with parallel unpacking: the "rebase" capability defers the parent to Commit time, so a commit-at-Prepare layer ends up parentless. The erofs snapshotter therefore had to disable rebase whenever the cache was enabled, making every cache *miss* fall back to a fully sequential (slower-than-cold) pull. Introduce snapshots.ErrAlreadyStaged, returned from Prepare to mean "the active snapshot's content is staged; skip the layer download and apply, but still Commit it" (where the parent is applied). Unlike ErrAlreadyExists it does not end the layer's lifecycle. The unpacker handles it by emitting a status whose bottom half runs the normal serialized commit (rebasing the parent in), and the metadata snapshotter threads it through Prepare like a normal active snapshot. The erofs cache hit now stages the blob and returns ErrAlreadyStaged instead of committing, so it can advertise "rebase" unconditionally: hits skip download+conversion and misses stay parallel. Also promote the "rebase" capability string to snapshots.RebaseCap (shared by the unpacker, erofs, and overlay). Follow up: fetch is range-based, so only a fully cached contiguous prefix skips downloads; a miss in a lower layer still pulls everything above it. Per-layer fetch-skip is left as a follow-up. Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>
110 lines
3.4 KiB
Go
110 lines
3.4 KiB
Go
//go:build linux
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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package overlay
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import (
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"errors"
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"github.com/moby/sys/userns"
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"github.com/containerd/containerd/v2/core/snapshots"
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"github.com/containerd/containerd/v2/plugins"
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"github.com/containerd/containerd/v2/plugins/snapshots/overlay"
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"github.com/containerd/containerd/v2/plugins/snapshots/overlay/overlayutils"
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"github.com/containerd/platforms"
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"github.com/containerd/plugin"
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"github.com/containerd/plugin/registry"
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)
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const (
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capaRemapIDs = "remap-ids"
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capaOnlyRemapIDs = "only-remap-ids"
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)
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// Config represents configuration for the overlay plugin.
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type Config struct {
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// Root directory for the plugin
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RootPath string `toml:"root_path"`
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UpperdirLabel bool `toml:"upperdir_label"`
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SyncRemove bool `toml:"sync_remove"`
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// slowChown allows the plugin to fallback to a recursive chown if fast options (like
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// idmap mounts) are not available. See more info about the overhead this can have in
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// github.com/containerd/containerd/docs/user-namespaces/.
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SlowChown bool `toml:"slow_chown"`
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// MountOptions are options used for the overlay mount (not used on bind mounts)
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MountOptions []string `toml:"mount_options"`
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}
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func init() {
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registry.Register(&plugin.Registration{
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Type: plugins.SnapshotPlugin,
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ID: "overlayfs",
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Config: &Config{},
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InitFn: func(ic *plugin.InitContext) (any, error) {
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ic.Meta.Platforms = append(ic.Meta.Platforms, platforms.DefaultSpec())
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config, ok := ic.Config.(*Config)
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if !ok {
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return nil, errors.New("invalid overlay configuration")
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}
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root := ic.Properties[plugins.PropertyRootDir]
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if config.RootPath != "" {
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root = config.RootPath
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}
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var oOpts []overlay.Opt
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if config.UpperdirLabel {
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oOpts = append(oOpts, overlay.WithUpperdirLabel)
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}
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if !config.SyncRemove {
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oOpts = append(oOpts, overlay.AsynchronousRemove)
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}
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if len(config.MountOptions) > 0 {
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oOpts = append(oOpts, overlay.WithMountOptions(config.MountOptions))
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}
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if ok, err := overlayutils.SupportsIDMappedMounts(); err == nil && ok {
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oOpts = append(oOpts, overlay.WithRemapIDs)
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ic.Meta.Capabilities = append(ic.Meta.Capabilities, capaRemapIDs)
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}
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if config.SlowChown {
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oOpts = append(oOpts, overlay.WithSlowChown)
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} else {
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// If slowChown is false, we use capaOnlyRemapIDs to signal we only
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// allow idmap mounts.
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ic.Meta.Capabilities = append(ic.Meta.Capabilities, capaOnlyRemapIDs)
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}
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if !userns.RunningInUserNS() {
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// "rebase" capability depends on `mknod c 0 0` via OverlayConvertWhiteout,
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// so it does not work when running in UserNS.
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// https://github.com/containerd/containerd/issues/13388
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ic.Meta.Capabilities = append(ic.Meta.Capabilities, snapshots.RebaseCap)
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}
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ic.Meta.Exports[plugins.SnapshotterRootDir] = root
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return overlay.NewSnapshotter(root, oOpts...)
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},
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})
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}
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