swarm/api: support mounting manifests via FUSE (#3690)

vendor/bazil.org/fuse/options.go

@@ -0,0 +1,310 @@
+package fuse
+
+import (
+	"errors"
+	"strings"
+)
+
+func dummyOption(conf *mountConfig) error {
+	return nil
+}
+
+// mountConfig holds the configuration for a mount operation.
+// Use it by passing MountOption values to Mount.
+type mountConfig struct {
+	options          map[string]string
+	maxReadahead     uint32
+	initFlags        InitFlags
+	osxfuseLocations []OSXFUSEPaths
+}
+
+func escapeComma(s string) string {
+	s = strings.Replace(s, `\`, `\\`, -1)
+	s = strings.Replace(s, `,`, `\,`, -1)
+	return s
+}
+
+// getOptions makes a string of options suitable for passing to FUSE
+// mount flag `-o`. Returns an empty string if no options were set.
+// Any platform specific adjustments should happen before the call.
+func (m *mountConfig) getOptions() string {
+	var opts []string
+	for k, v := range m.options {
+		k = escapeComma(k)
+		if v != "" {
+			k += "=" + escapeComma(v)
+		}
+		opts = append(opts, k)
+	}
+	return strings.Join(opts, ",")
+}
+
+type mountOption func(*mountConfig) error
+
+// MountOption is passed to Mount to change the behavior of the mount.
+type MountOption mountOption
+
+// FSName sets the file system name (also called source) that is
+// visible in the list of mounted file systems.
+//
+// FreeBSD ignores this option.
+func FSName(name string) MountOption {
+	return func(conf *mountConfig) error {
+		conf.options["fsname"] = name
+		return nil
+	}
+}
+
+// Subtype sets the subtype of the mount. The main type is always
+// `fuse`. The type in a list of mounted file systems will look like
+// `fuse.foo`.
+//
+// OS X ignores this option.
+// FreeBSD ignores this option.
+func Subtype(fstype string) MountOption {
+	return func(conf *mountConfig) error {
+		conf.options["subtype"] = fstype
+		return nil
+	}
+}
+
+// LocalVolume sets the volume to be local (instead of network),
+// changing the behavior of Finder, Spotlight, and such.
+//
+// OS X only. Others ignore this option.
+func LocalVolume() MountOption {
+	return localVolume
+}
+
+// VolumeName sets the volume name shown in Finder.
+//
+// OS X only. Others ignore this option.
+func VolumeName(name string) MountOption {
+	return volumeName(name)
+}
+
+// NoAppleDouble makes OSXFUSE disallow files with names used by OS X
+// to store extended attributes on file systems that do not support
+// them natively.
+//
+// Such file names are:
+//
+//     ._*
+//     .DS_Store
+//
+// OS X only.  Others ignore this option.
+func NoAppleDouble() MountOption {
+	return noAppleDouble
+}
+
+// NoAppleXattr makes OSXFUSE disallow extended attributes with the
+// prefix "com.apple.". This disables persistent Finder state and
+// other such information.
+//
+// OS X only.  Others ignore this option.
+func NoAppleXattr() MountOption {
+	return noAppleXattr
+}
+
+// ExclCreate causes O_EXCL flag to be set for only "truly" exclusive creates,
+// i.e. create calls for which the initiator explicitly set the O_EXCL flag.
+//
+// OSXFUSE expects all create calls to return EEXIST in case the file
+// already exists, regardless of whether O_EXCL was specified or not.
+// To ensure this behavior, it normally sets OpenExclusive for all
+// Create calls, regardless of whether the original call had it set.
+// For distributed filesystems, that may force every file create to be
+// a distributed consensus action, causing undesirable delays.
+//
+// This option makes the FUSE filesystem see the original flag value,
+// and better decide when to ensure global consensus.
+//
+// Note that returning EEXIST on existing file create is still
+// expected with OSXFUSE, regardless of the presence of the
+// OpenExclusive flag.
+//
+// For more information, see
+// https://github.com/osxfuse/osxfuse/issues/209
+//
+// OS X only. Others ignore this options.
+// Requires OSXFUSE 3.4.1 or newer.
+func ExclCreate() MountOption {
+	return exclCreate
+}
+
+// DaemonTimeout sets the time in seconds between a request and a reply before
+// the FUSE mount is declared dead.
+//
+// OS X and FreeBSD only. Others ignore this option.
+func DaemonTimeout(name string) MountOption {
+	return daemonTimeout(name)
+}
+
+var ErrCannotCombineAllowOtherAndAllowRoot = errors.New("cannot combine AllowOther and AllowRoot")
+
+// AllowOther allows other users to access the file system.
+//
+// Only one of AllowOther or AllowRoot can be used.
+func AllowOther() MountOption {
+	return func(conf *mountConfig) error {
+		if _, ok := conf.options["allow_root"]; ok {
+			return ErrCannotCombineAllowOtherAndAllowRoot
+		}
+		conf.options["allow_other"] = ""
+		return nil
+	}
+}
+
+// AllowRoot allows other users to access the file system.
+//
+// Only one of AllowOther or AllowRoot can be used.
+//
+// FreeBSD ignores this option.
+func AllowRoot() MountOption {
+	return func(conf *mountConfig) error {
+		if _, ok := conf.options["allow_other"]; ok {
+			return ErrCannotCombineAllowOtherAndAllowRoot
+		}
+		conf.options["allow_root"] = ""
+		return nil
+	}
+}
+
+// AllowDev enables interpreting character or block special devices on the
+// filesystem.
+func AllowDev() MountOption {
+	return func(conf *mountConfig) error {
+		conf.options["dev"] = ""
+		return nil
+	}
+}
+
+// AllowSUID allows set-user-identifier or set-group-identifier bits to take
+// effect.
+func AllowSUID() MountOption {
+	return func(conf *mountConfig) error {
+		conf.options["suid"] = ""
+		return nil
+	}
+}
+
+// DefaultPermissions makes the kernel enforce access control based on
+// the file mode (as in chmod).
+//
+// Without this option, the Node itself decides what is and is not
+// allowed. This is normally ok because FUSE file systems cannot be
+// accessed by other users without AllowOther/AllowRoot.
+//
+// FreeBSD ignores this option.
+func DefaultPermissions() MountOption {
+	return func(conf *mountConfig) error {
+		conf.options["default_permissions"] = ""
+		return nil
+	}
+}
+
+// ReadOnly makes the mount read-only.
+func ReadOnly() MountOption {
+	return func(conf *mountConfig) error {
+		conf.options["ro"] = ""
+		return nil
+	}
+}
+
+// MaxReadahead sets the number of bytes that can be prefetched for
+// sequential reads. The kernel can enforce a maximum value lower than
+// this.
+//
+// This setting makes the kernel perform speculative reads that do not
+// originate from any client process. This usually tremendously
+// improves read performance.
+func MaxReadahead(n uint32) MountOption {
+	return func(conf *mountConfig) error {
+		conf.maxReadahead = n
+		return nil
+	}
+}
+
+// AsyncRead enables multiple outstanding read requests for the same
+// handle. Without this, there is at most one request in flight at a
+// time.
+func AsyncRead() MountOption {
+	return func(conf *mountConfig) error {
+		conf.initFlags |= InitAsyncRead
+		return nil
+	}
+}
+
+// WritebackCache enables the kernel to buffer writes before sending
+// them to the FUSE server. Without this, writethrough caching is
+// used.
+func WritebackCache() MountOption {
+	return func(conf *mountConfig) error {
+		conf.initFlags |= InitWritebackCache
+		return nil
+	}
+}
+
+// OSXFUSEPaths describes the paths used by an installed OSXFUSE
+// version. See OSXFUSELocationV3 for typical values.
+type OSXFUSEPaths struct {
+	// Prefix for the device file. At mount time, an incrementing
+	// number is suffixed until a free FUSE device is found.
+	DevicePrefix string
+	// Path of the load helper, used to load the kernel extension if
+	// no device files are found.
+	Load string
+	// Path of the mount helper, used for the actual mount operation.
+	Mount string
+	// Environment variable used to pass the path to the executable
+	// calling the mount helper.
+	DaemonVar string
+}
+
+// Default paths for OSXFUSE. See OSXFUSELocations.
+var (
+	OSXFUSELocationV3 = OSXFUSEPaths{
+		DevicePrefix: "/dev/osxfuse",
+		Load:         "/Library/Filesystems/osxfuse.fs/Contents/Resources/load_osxfuse",
+		Mount:        "/Library/Filesystems/osxfuse.fs/Contents/Resources/mount_osxfuse",
+		DaemonVar:    "MOUNT_OSXFUSE_DAEMON_PATH",
+	}
+	OSXFUSELocationV2 = OSXFUSEPaths{
+		DevicePrefix: "/dev/osxfuse",
+		Load:         "/Library/Filesystems/osxfusefs.fs/Support/load_osxfusefs",
+		Mount:        "/Library/Filesystems/osxfusefs.fs/Support/mount_osxfusefs",
+		DaemonVar:    "MOUNT_FUSEFS_DAEMON_PATH",
+	}
+)
+
+// OSXFUSELocations sets where to look for OSXFUSE files. The
+// arguments are all the possible locations. The previous locations
+// are replaced.
+//
+// Without this option, OSXFUSELocationV3 and OSXFUSELocationV2 are
+// used.
+//
+// OS X only. Others ignore this option.
+func OSXFUSELocations(paths ...OSXFUSEPaths) MountOption {
+	return func(conf *mountConfig) error {
+		if len(paths) == 0 {
+			return errors.New("must specify at least one location for OSXFUSELocations")
+		}
+		// replace previous values, but make a copy so there's no
+		// worries about caller mutating their slice
+		conf.osxfuseLocations = append(conf.osxfuseLocations[:0], paths...)
+		return nil
+	}
+}
+
+// AllowNonEmptyMount allows the mounting over a non-empty directory.
+//
+// The files in it will be shadowed by the freshly created mount. By
+// default these mounts are rejected to prevent accidental covering up
+// of data, which could for example prevent automatic backup.
+func AllowNonEmptyMount() MountOption {
+	return func(conf *mountConfig) error {
+		conf.options["nonempty"] = ""
+		return nil
+	}
+}