syscallcompat: Getdents: warn once if we get DT_UNKNOWN

...and if Getdents is not available at all.

Due to this warning I now know that SSHFS always returns DT_UNKNOWN:

    gocryptfs[8129]: Getdents: convertDType: received DT_UNKNOWN, falling back to Lstat

This behavoir is confirmed at http://ahefner.livejournal.com/16875.html:

    "With sshfs, I finally found that obscure case. The dtype is always set to DT_UNKNOWN [...]"

2 files changed, 12 insertions, 0 deletions

diff --git a/internal/fusefrontend/fs_dir.go b/internal/fusefrontend/fs_dir.go
index 211eeea..c87cc02 100644
--- a/internal/fusefrontend/fs_dir.go
+++ b/internal/fusefrontend/fs_dir.go
@@ -7,6 +7,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"sync"
 	"syscall"
 
 	"github.com/hanwen/go-fuse/fuse"
@@ -234,6 +235,8 @@ func (fs *FS) Rmdir(path string, context *fuse.Context) (code fuse.Status) {
 	return fuse.OK
 }
 
+var haveGetdentsWarnOnce sync.Once
+
 // OpenDir implements pathfs.FileSystem
 func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, fuse.Status) {
 	tlog.Debug.Printf("OpenDir(%s)", dirName)
@@ -252,6 +255,9 @@ func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, f
 			return nil, fuse.ToStatus(err)
 		}
 	} else {
+		haveGetdentsWarnOnce.Do(func() {
+			tlog.Warn.Printf("OpenDir: Getdents not available, falling back to OpenDir")
+		})
 		cipherEntries, status = fs.FileSystem.OpenDir(cDirName, context)
 		if !status.Ok() {
 			return nil, status
diff --git a/internal/syscallcompat/getdents_linux.go b/internal/syscallcompat/getdents_linux.go
index 97cd75f..55bffff 100644
--- a/internal/syscallcompat/getdents_linux.go
+++ b/internal/syscallcompat/getdents_linux.go
@@ -8,6 +8,7 @@ package syscallcompat
 
 import (
 	"bytes"
+	"sync"
 	"syscall"
 	"unsafe"
 
@@ -121,6 +122,8 @@ func getdentsName(s syscall.Dirent) (string, error) {
 	return string(name), nil
 }
 
+var dtUnknownWarnOnce sync.Once
+
 // convertDType converts a Dirent.Type to at Stat_t.Mode value.
 func convertDType(dtype uint8, file string) (uint32, error) {
 	if dtype != syscall.DT_UNKNOWN {
@@ -128,6 +131,9 @@ func convertDType(dtype uint8, file string) (uint32, error) {
 		return uint32(dtype) << 12, nil
 	}
 	// DT_UNKNOWN: we have to call Lstat()
+	dtUnknownWarnOnce.Do(func() {
+		tlog.Warn.Printf("Getdents: convertDType: received DT_UNKNOWN, falling back to Lstat")
+	})
 	var st syscall.Stat_t
 	err := syscall.Lstat(file, &st)
 	if err != nil {