cephfs: add functions for Init and SetMountPerms

The Init functions initializes the connection without mounting the fs.
This function must be called before setting the perms but before
creating the mount.

SetMountPerms accepts a UserPerm object to set the fs ownership info
on the mount. The corresponding tests verifies that the UserPerm
can be applied and it effects the gid of newly created dirs for that
mount.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

cephfs/cephfs.go

@@ -96,6 +96,14 @@ func (mount *MountInfo) GetConfigOption(option string) (string, error) {
 	return value, nil
 }
 
+// Init the file system client without actually mounting the file system.
+//
+// Implements:
+//  int ceph_init(struct ceph_mount_info *cmount);
+func (mount *MountInfo) Init() error {
+	return getError(C.ceph_init(mount.mount))
+}
+
 // Mount the file system, establishing a connection capable of I/O.
 //
 // Implements:

cephfs/mount_perms_mimic.go

@@ -0,0 +1,22 @@
+// +build !luminous
+//
+// ceph_mount_perms_set available in mimic & later
+
+package cephfs
+
+/*
+#cgo LDFLAGS: -lcephfs
+#cgo CPPFLAGS: -D_FILE_OFFSET_BITS=64
+#include <cephfs/libcephfs.h>
+*/
+import "C"
+
+// SetMountPerms applies the given UserPerm to the mount object, which it will
+// then use to define the connection's ownership credentials.
+// This function must be called after Init but before Mount.
+//
+// Implements:
+//  int ceph_mount_perms_set(struct ceph_mount_info *cmount, UserPerm *perm);
+func (mount *MountInfo) SetMountPerms(perm *UserPerm) error {
+	return getError(C.ceph_mount_perms_set(mount.mount, perm.userPerm))
+}

cephfs/mount_perms_mimic_test.go

@@ -0,0 +1,45 @@
+// +build !luminous
+
+package cephfs
+
+import (
+	"os"
+	"path"
+	"syscall"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSetMountPerms(t *testing.T) {
+	mount, err := CreateMount()
+	require.NoError(t, err)
+	require.NotNil(t, mount)
+	defer func() { assert.NoError(t, mount.Release()) }()
+
+	err = mount.ReadDefaultConfigFile()
+	require.NoError(t, err)
+
+	err = mount.Init()
+	assert.NoError(t, err)
+
+	uperm := NewUserPerm(0, 500, []int{0, 500, 501})
+	err = mount.SetMountPerms(uperm)
+	assert.NoError(t, err)
+
+	err = mount.Mount()
+	assert.NoError(t, err)
+	defer func() { assert.NoError(t, mount.Unmount()) }()
+
+	t.Run("checkStat", func(t *testing.T) {
+		useMount(t)
+		dirname := "/check-mount-perms"
+		err := mount.MakeDir(dirname, 0755)
+		assert.NoError(t, err)
+		defer mount.RemoveDir(dirname)
+		s, err := os.Stat(path.Join(CephMountDir, dirname))
+		require.NoError(t, err)
+		assert.EqualValues(t, s.Sys().(*syscall.Stat_t).Gid, 500)
+	})
+}