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Lessen mount lock contention in layer store #39135

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Merged
kolyshkin merged 2 commits into from
May 9, 2019
Merged

Lessen mount lock contention in layer store #39135

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f73b5cb
layer: protect mountedLayer.references
kolyshkin May 3, 2019
05250a4
layer: optimize layerStore mountL
xinfengliu Apr 23, 2019
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50 changes: 32 additions & 18 deletions layer/layer_store.go
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Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,9 @@ func (ls *layerStore) loadLayer(layer ChainID) (*roLayer, error) {
}

func (ls *layerStore) loadMount(mount string) error {
if _, ok := ls.mounts[mount]; ok {
ls.mountL.Lock()
defer ls.mountL.Unlock()
if m := ls.mounts[mount]; m != nil {
return nil
}

Expand Down Expand Up @@ -477,7 +479,7 @@ func (ls *layerStore) Release(l Layer) ([]Metadata, error) {
return ls.releaseLayer(layer)
}

func (ls *layerStore) CreateRWLayer(name string, parent ChainID, opts *CreateRWLayerOpts) (RWLayer, error) {
func (ls *layerStore) CreateRWLayer(name string, parent ChainID, opts *CreateRWLayerOpts) (_ RWLayer, err error) {
var (
storageOpt map[string]string
initFunc MountInit
Expand All @@ -491,13 +493,21 @@ func (ls *layerStore) CreateRWLayer(name string, parent ChainID, opts *CreateRWL
}

ls.mountL.Lock()
defer ls.mountL.Unlock()
m, ok := ls.mounts[name]
if ok {
if _, ok := ls.mounts[name]; ok {
ls.mountL.Unlock()
return nil, ErrMountNameConflict
}
// Avoid name collision by temporary assigning nil
ls.mounts[name] = nil
ls.mountL.Unlock()
defer func() {
if err != nil {
ls.mountL.Lock()
delete(ls.mounts, name)
ls.mountL.Unlock()
}
}()

var err error
var pid string
var p *roLayer
if string(parent) != "" {
Expand All @@ -517,7 +527,7 @@ func (ls *layerStore) CreateRWLayer(name string, parent ChainID, opts *CreateRWL
}()
}

m = &mountedLayer{
m := &mountedLayer{
name: name,
parent: p,
mountID: ls.mountID(name),
Expand All @@ -528,7 +538,7 @@ func (ls *layerStore) CreateRWLayer(name string, parent ChainID, opts *CreateRWL
if initFunc != nil {
pid, err = ls.initMount(m.mountID, pid, mountLabel, initFunc, storageOpt)
if err != nil {
return nil, err
return
}
m.initID = pid
}
Expand All @@ -538,20 +548,20 @@ func (ls *layerStore) CreateRWLayer(name string, parent ChainID, opts *CreateRWL
}

if err = ls.driver.CreateReadWrite(m.mountID, pid, createOpts); err != nil {
return nil, err
return
}
if err = ls.saveMount(m); err != nil {
return nil, err
return
}

return m.getReference(), nil
}

func (ls *layerStore) GetRWLayer(id string) (RWLayer, error) {
ls.mountL.Lock()
defer ls.mountL.Unlock()
mount, ok := ls.mounts[id]
if !ok {
mount := ls.mounts[id]
ls.mountL.Unlock()
if mount == nil {
return nil, ErrMountDoesNotExist
}

Expand All @@ -561,8 +571,8 @@ func (ls *layerStore) GetRWLayer(id string) (RWLayer, error) {
func (ls *layerStore) GetMountID(id string) (string, error) {
ls.mountL.Lock()
defer ls.mountL.Unlock()
mount, ok := ls.mounts[id]
if !ok {
mount := ls.mounts[id]
if mount == nil {
return "", ErrMountDoesNotExist
}
logrus.Debugf("GetMountID id: %s -> mountID: %s", id, mount.mountID)
Expand All @@ -572,9 +582,9 @@ func (ls *layerStore) GetMountID(id string) (string, error) {

func (ls *layerStore) ReleaseRWLayer(l RWLayer) ([]Metadata, error) {
ls.mountL.Lock()
defer ls.mountL.Unlock()
m, ok := ls.mounts[l.Name()]
if !ok {
m := ls.mounts[l.Name()]
ls.mountL.Unlock()
if m == nil {
return []Metadata{}, nil
}

Expand Down Expand Up @@ -606,7 +616,9 @@ func (ls *layerStore) ReleaseRWLayer(l RWLayer) ([]Metadata, error) {
return nil, err
}

ls.mountL.Lock()
delete(ls.mounts, m.Name())
ls.mountL.Unlock()

ls.layerL.Lock()
defer ls.layerL.Unlock()
Expand Down Expand Up @@ -634,7 +646,9 @@ func (ls *layerStore) saveMount(mount *mountedLayer) error {
}
}

ls.mountL.Lock()
ls.mounts[mount.name] = mount
ls.mountL.Unlock()

return nil
}
Expand Down
6 changes: 3 additions & 3 deletions layer/migration.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,9 +18,9 @@ import (
// after migration the layer may be retrieved by the given name.
func (ls *layerStore) CreateRWLayerByGraphID(name, graphID string, parent ChainID) (err error) {
ls.mountL.Lock()
defer ls.mountL.Unlock()
m, ok := ls.mounts[name]
if ok {
m := ls.mounts[name]
ls.mountL.Unlock()
if m != nil {
if m.parent.chainID != parent {
return errors.New("name conflict, mismatched parent")
}
Expand Down
14 changes: 13 additions & 1 deletion layer/mounted_layer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ package layer // import "github.com/docker/docker/layer"

import (
"io"
"sync"

"github.com/docker/docker/pkg/archive"
"github.com/docker/docker/pkg/containerfs"
Expand All @@ -15,6 +16,7 @@ type mountedLayer struct {
path string
layerStore *layerStore

sync.Mutex
references map[RWLayer]*referencedRWLayer
}

Expand Down Expand Up @@ -62,16 +64,24 @@ func (ml *mountedLayer) getReference() RWLayer {
ref := &referencedRWLayer{
mountedLayer: ml,
}
ml.Lock()
ml.references[ref] = ref
ml.Unlock()

return ref
}

func (ml *mountedLayer) hasReferences() bool {
return len(ml.references) > 0
ml.Lock()
ret := len(ml.references) > 0
ml.Unlock()

return ret
}

func (ml *mountedLayer) deleteReference(ref RWLayer) error {
ml.Lock()
defer ml.Unlock()
if _, ok := ml.references[ref]; !ok {
return ErrLayerNotRetained
}
Expand All @@ -81,7 +91,9 @@ func (ml *mountedLayer) deleteReference(ref RWLayer) error {

func (ml *mountedLayer) retakeReference(r RWLayer) {
if ref, ok := r.(*referencedRWLayer); ok {
ml.Lock()
ml.references[ref] = ref
ml.Unlock()
}
}

Expand Down