Simplify and fix os.MkdirAll() usage

TL;DR: check for IsExist(err) after a failed MkdirAll() is both
redundant and wrong -- so two reasons to remove it.

Quoting MkdirAll documentation:

> MkdirAll creates a directory named path, along with any necessary
> parents, and returns nil, or else returns an error. If path
> is already a directory, MkdirAll does nothing and returns nil.

This means two things:

1. If a directory to be created already exists, no error is returned.

2. If the error returned is IsExist (EEXIST), it means there exists
a non-directory with the same name as MkdirAll need to use for
directory. Example: we want to MkdirAll("a/b"), but file "a"
(or "a/b") already exists, so MkdirAll fails.

The above is a theory, based on quoted documentation and my UNIX
knowledge.

3. In practice, though, current MkdirAll implementation [1] returns
ENOTDIR in most of cases described in #2, with the exception when
there is a race between MkdirAll and someone else creating the
last component of MkdirAll argument as a file. In this very case
MkdirAll() will indeed return EEXIST.

Because of #1, IsExist check after MkdirAll is not needed.

Because of #2 and #3, ignoring IsExist error is just plain wrong,
as directory we require is not created. It's cleaner to report
the error now.

Note this error is all over the tree, I guess due to copy-paste,
or trying to follow the same usage pattern as for Mkdir(),
or some not quite correct examples on the Internet.

[v2: a separate aufs commit is merged into this one]

[1] https://github.com/golang/go/blob/f9ed2f75/src/os/path.go

Signed-off-by: Kir Kolyshkin <kir@openvz.org>

daemon/daemon.go

@@ -582,7 +582,7 @@ func NewDaemon(config *Config, registryService *registry.Service) (daemon *Daemo
 	}
 	config.Root = realRoot
 	// Create the root directory if it doesn't exists
-	if err := system.MkdirAll(config.Root, 0700); err != nil && !os.IsExist(err) {
+	if err := system.MkdirAll(config.Root, 0700); err != nil {
 		return nil, err
 	}
 
@@ -634,7 +634,7 @@ func NewDaemon(config *Config, registryService *registry.Service) (daemon *Daemo
 
 	daemonRepo := filepath.Join(config.Root, "containers")
 
-	if err := system.MkdirAll(daemonRepo, 0700); err != nil && !os.IsExist(err) {
+	if err := system.MkdirAll(daemonRepo, 0700); err != nil {
 		return nil, err
 	}
 
@@ -661,7 +661,7 @@ func NewDaemon(config *Config, registryService *registry.Service) (daemon *Daemo
 
 	trustDir := filepath.Join(config.Root, "trust")
 
-	if err := system.MkdirAll(trustDir, 0700); err != nil && !os.IsExist(err) {
+	if err := system.MkdirAll(trustDir, 0700); err != nil {
 		return nil, err
 	}
 	trustService, err := trust.NewTrustStore(trustDir)

daemon/graphdriver/aufs/aufs.go

@@ -104,13 +104,8 @@ func Init(root string, options []string) (graphdriver.Driver, error) {
 		active: make(map[string]int),
 	}
 
-	// Create the root aufs driver dir and return
-	// if it already exists
-	// If not populate the dir structure
+	// Create the root aufs driver dir
 	if err := os.MkdirAll(root, 0755); err != nil {
-		if os.IsExist(err) {
-			return a, nil
-		}
 		return nil, err
 	}
 
@@ -118,6 +113,7 @@ func Init(root string, options []string) (graphdriver.Driver, error) {
 		return nil, err
 	}
 
+	// Populate the dir structure
 	for _, p := range paths {
 		if err := os.MkdirAll(path.Join(root, p), 0755); err != nil {
 			return nil, err

daemon/graphdriver/devmapper/deviceset.go

@@ -238,7 +238,7 @@ func (devices *DeviceSet) ensureImage(name string, size int64) (string, error) {
 	dirname := devices.loopbackDir()
 	filename := path.Join(dirname, name)
 
-	if err := os.MkdirAll(dirname, 0700); err != nil && !os.IsExist(err) {
+	if err := os.MkdirAll(dirname, 0700); err != nil {
 		return "", err
 	}
 
@@ -1260,7 +1260,7 @@ func (devices *DeviceSet) initDevmapper(doInit bool) error {
 		logrus.Warn("Udev sync is not supported. This will lead to unexpected behavior, data loss and errors. For more information, see https://docs.docker.com/reference/commandline/cli/#daemon-storage-driver-option")
 	}
 
-	if err := os.MkdirAll(devices.metadataDir(), 0700); err != nil && !os.IsExist(err) {
+	if err := os.MkdirAll(devices.metadataDir(), 0700); err != nil {
 		return err
 	}
 

daemon/graphdriver/devmapper/driver.go

@@ -159,7 +159,7 @@ func (d *Driver) Get(id, mountLabel string) (string, error) {
 	mp := path.Join(d.home, "mnt", id)
 
 	// Create the target directories if they don't exist
-	if err := os.MkdirAll(mp, 0755); err != nil && !os.IsExist(err) {
+	if err := os.MkdirAll(mp, 0755); err != nil {
 		return "", err
 	}
 
@@ -169,7 +169,7 @@ func (d *Driver) Get(id, mountLabel string) (string, error) {
 	}
 
 	rootFs := path.Join(mp, "rootfs")
-	if err := os.MkdirAll(rootFs, 0755); err != nil && !os.IsExist(err) {
+	if err := os.MkdirAll(rootFs, 0755); err != nil {
 		d.DeviceSet.UnmountDevice(id)
 		return "", err
 	}

daemon/graphdriver/overlay/overlay.go

@@ -124,7 +124,7 @@ func Init(home string, options []string) (graphdriver.Driver, error) {
 	}
 
 	// Create the driver home dir
-	if err := os.MkdirAll(home, 0755); err != nil && !os.IsExist(err) {
+	if err := os.MkdirAll(home, 0755); err != nil {
 		return nil, err
 	}
 

daemon/graphdriver/zfs/zfs.go

@@ -280,7 +280,7 @@ func (d *Driver) Get(id, mountLabel string) (string, error) {
 	logrus.Debugf(`[zfs] mount("%s", "%s", "%s")`, filesystem, mountpoint, options)
 
 	// Create the target directories if they don't exist
-	if err := os.MkdirAll(mountpoint, 0755); err != nil && !os.IsExist(err) {
+	if err := os.MkdirAll(mountpoint, 0755); err != nil {
 		return "", err
 	}
 

graph/graph.go

@@ -107,7 +107,7 @@ func NewGraph(root string, driver graphdriver.Driver) (*Graph, error) {
 		return nil, err
 	}
 	// Create the root directory if it doesn't exists
-	if err := system.MkdirAll(root, 0700); err != nil && !os.IsExist(err) {
+	if err := system.MkdirAll(root, 0700); err != nil {
 		return nil, err
 	}
 

integration-cli/docker_utils.go

@@ -1187,7 +1187,7 @@ func newFakeGit(name string, files map[string]string, enforceLocalServer bool) (
 // Call c.Fatal() at the first error.
 func writeFile(dst, content string, c *check.C) {
 	// Create subdirectories if necessary
-	if err := os.MkdirAll(path.Dir(dst), 0700); err != nil && !os.IsExist(err) {
+	if err := os.MkdirAll(path.Dir(dst), 0700); err != nil {
 		c.Fatal(err)
 	}
 	f, err := os.OpenFile(dst, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0700)

pkg/archive/archive.go

@@ -714,7 +714,7 @@ func (archiver *Archiver) CopyWithTar(src, dst string) error {
 	}
 	// Create dst, copy src's content into it
 	logrus.Debugf("Creating dest directory: %s", dst)
-	if err := system.MkdirAll(dst, 0755); err != nil && !os.IsExist(err) {
+	if err := system.MkdirAll(dst, 0755); err != nil {
 		return err
 	}
 	logrus.Debugf("Calling TarUntar(%s, %s)", src, dst)
@@ -746,7 +746,7 @@ func (archiver *Archiver) CopyFileWithTar(src, dst string) (err error) {
 		dst = filepath.Join(dst, filepath.Base(src))
 	}
 	// Create the holding directory if necessary
-	if err := system.MkdirAll(filepath.Dir(dst), 0700); err != nil && !os.IsExist(err) {
+	if err := system.MkdirAll(filepath.Dir(dst), 0700); err != nil {
 		return err
 	}