Reapply the fix from #1054, but without getting into an infinite look…

… in case of SMB fs errors. See #1164

scanner/walk_dir_tree.go

@@ -66,11 +66,14 @@ func loadDir(ctx context.Context, dirPath string) ([]string, *dirStats, error) {
 	}
 	stats.ModTime = dirInfo.ModTime()
 
-	dirEntries, err := fullReadDir(dirPath)
+	dir, err := os.Open(dirPath)
 	if err != nil {
-		log.Error(ctx, "Error in ReadDir", "path", dirPath, err)
+		log.Error(ctx, "Error in Opening directory", "path", dirPath, err)
 		return children, stats, err
 	}
+	defer dir.Close()
+
+	dirEntries := fullReadDir(ctx, dir)
 	for _, entry := range dirEntries {
 		isDir, err := isDirOrSymlinkToDir(dirPath, entry)
 		// Skip invalid symlinks
@@ -100,20 +103,28 @@ func loadDir(ctx context.Context, dirPath string) ([]string, *dirStats, error) {
 	return children, stats, nil
 }
 
-func fullReadDir(name string) ([]os.DirEntry, error) {
-	f, err := os.Open(name)
-	if err != nil {
-		return nil, err
-	}
-	defer f.Close()
-
-	dirs, err := f.ReadDir(-1)
-	if err != nil {
-		log.Warn("Skipping DirEntry", err)
-		return nil, nil
+// fullReadDir reads all files in the folder, skipping the ones with errors.
+// It also detects when it is "stuck" with an error in the same directory over and over.
+// In this case, it and returns whatever it was able to read until it got stuck.
+// See discussion here: https://github.com/navidrome/navidrome/issues/1164#issuecomment-881922850
+func fullReadDir(ctx context.Context, dir fs.ReadDirFile) []os.DirEntry {
+	var allDirs []os.DirEntry
+	var prevErrStr = ""
+	for {
+		dirs, err := dir.ReadDir(-1)
+		allDirs = append(allDirs, dirs...)
+		if err == nil {
+			break
+		}
+		log.Warn(ctx, "Skipping DirEntry", err)
+		if prevErrStr == err.Error() {
+			log.Error(ctx, "Duplicate DirEntry failure, bailing", err)
+			break
+		}
+		prevErrStr = err.Error()
 	}
-	sort.Slice(dirs, func(i, j int) bool { return dirs[i].Name() < dirs[j].Name() })
-	return dirs, nil
+	sort.Slice(allDirs, func(i, j int) bool { return allDirs[i].Name() < allDirs[j].Name() })
+	return allDirs
 }
 
 // isDirOrSymlinkToDir returns true if and only if the dirEnt represents a file

scanner/walk_dir_tree_test.go

@@ -2,8 +2,10 @@ package scanner
 
 import (
 	"context"
+	"io/fs"
 	"os"
 	"path/filepath"
+	"testing/fstest"
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
@@ -78,8 +80,85 @@ var _ = Describe("walk_dir_tree", func() {
 			Expect(isDirIgnored(baseDir, dirEntry)).To(BeFalse())
 		})
 	})
+
+	Describe("fullReadDir", func() {
+		var fsys fakeFS
+		var ctx context.Context
+		BeforeEach(func() {
+			ctx = context.Background()
+			fsys = fakeFS{MapFS: fstest.MapFS{
+				"root/a/f1": {},
+				"root/b/f2": {},
+				"root/c/f3": {},
+			}}
+		})
+		It("reads all entries", func() {
+			dir, _ := fsys.Open("root")
+			entries := fullReadDir(ctx, dir.(fs.ReadDirFile))
+			Expect(entries).To(HaveLen(3))
+			Expect(entries[0].Name()).To(Equal("a"))
+			Expect(entries[1].Name()).To(Equal("b"))
+			Expect(entries[2].Name()).To(Equal("c"))
+		})
+		It("skips entries with permission error", func() {
+			fsys.failOn = "b"
+			dir, _ := fsys.Open("root")
+			entries := fullReadDir(ctx, dir.(fs.ReadDirFile))
+			Expect(entries).To(HaveLen(2))
+			Expect(entries[0].Name()).To(Equal("a"))
+			Expect(entries[1].Name()).To(Equal("c"))
+		})
+		It("aborts if it keeps getting 'readdirent: no such file or directory'", func() {
+			fsys.err = fs.ErrNotExist
+			dir, _ := fsys.Open("root")
+			entries := fullReadDir(ctx, dir.(fs.ReadDirFile))
+			Expect(entries).To(BeEmpty())
+		})
+	})
 })
 
+type fakeFS struct {
+	fstest.MapFS
+	failOn string
+	err    error
+}
+
+func (f *fakeFS) Open(name string) (fs.File, error) {
+	dir, err := f.MapFS.Open(name)
+	return &fakeDirFile{File: dir, fail: f.failOn, err: f.err}, err
+}
+
+type fakeDirFile struct {
+	fs.File
+	entries []fs.DirEntry
+	pos     int
+	fail    string
+	err     error
+}
+
+// Only works with n == -1
+func (fd *fakeDirFile) ReadDir(n int) ([]fs.DirEntry, error) {
+	if fd.err != nil {
+		return nil, fd.err
+	}
+	if fd.entries == nil {
+		fd.entries, _ = fd.File.(fs.ReadDirFile).ReadDir(-1)
+	}
+	var dirs []fs.DirEntry
+	for {
+		if fd.pos >= len(fd.entries) {
+			break
+		}
+		e := fd.entries[fd.pos]
+		fd.pos++
+		if e.Name() == fd.fail {
+			return dirs, &fs.PathError{Op: "lstat", Path: e.Name(), Err: fs.ErrPermission}
+		}
+		dirs = append(dirs, e)
+	}
+	return dirs, nil
+}
+
 func getDirEntry(baseDir, name string) (os.DirEntry, error) {
 	dirEntries, _ := os.ReadDir(baseDir)
 	for _, entry := range dirEntries {