diff --git a/lib/fs/basicfs.go b/lib/fs/basicfs.go
index 098769870..4ed60d10e 100644
--- a/lib/fs/basicfs.go
+++ b/lib/fs/basicfs.go
@@ -379,12 +379,12 @@ func longFilenameSupport(path string) string {
 	return path
 }
 
-type ErrWatchEventOutsideRoot struct{ msg string }
+type WatchEventOutsideRootError struct{ msg string }
 
-func (e *ErrWatchEventOutsideRoot) Error() string {
+func (e *WatchEventOutsideRootError) Error() string {
 	return e.msg
 }
 
-func (f *BasicFilesystem) newErrWatchEventOutsideRoot(absPath string, roots []string) *ErrWatchEventOutsideRoot {
-	return &ErrWatchEventOutsideRoot{fmt.Sprintf("Watching for changes encountered an event outside of the filesystem root: f.root==%v, roots==%v, path==%v. This should never happen, please report this message to forum.syncthing.net.", f.root, roots, absPath)}
+func (f *BasicFilesystem) newErrWatchEventOutsideRoot(absPath string, roots []string) *WatchEventOutsideRootError {
+	return &WatchEventOutsideRootError{fmt.Sprintf("Watching for changes encountered an event outside of the filesystem root: f.root==%v, roots==%v, path==%v. This should never happen, please report this message to forum.syncthing.net.", f.root, roots, absPath)}
 }
diff --git a/lib/fs/basicfs_fileinfo_bsdish.go b/lib/fs/basicfs_fileinfo_bsdish.go
index b8e60f329..10061ebfb 100644
--- a/lib/fs/basicfs_fileinfo_bsdish.go
+++ b/lib/fs/basicfs_fileinfo_bsdish.go
@@ -15,7 +15,7 @@ import (
 )
 
 func (fi basicFileInfo) InodeChangeTime() time.Time {
-	if sys, ok := fi.FileInfo.Sys().(*syscall.Stat_t); ok {
+	if sys, ok := fi.Sys().(*syscall.Stat_t); ok {
 		return time.Unix(0, sys.Ctimespec.Nano())
 	}
 	return time.Time{}
diff --git a/lib/fs/basicfs_unix.go b/lib/fs/basicfs_unix.go
index e1b3967eb..1a54b2652 100644
--- a/lib/fs/basicfs_unix.go
+++ b/lib/fs/basicfs_unix.go
@@ -86,7 +86,7 @@ func (f *BasicFilesystem) Remove(name string) error {
 // unrooted) or an error if the given path is not a subpath and handles the
 // special case when the given path is the folder root without a trailing
 // pathseparator.
-func (f *BasicFilesystem) unrootedChecked(absPath string, roots []string) (string, *ErrWatchEventOutsideRoot) {
+func (f *BasicFilesystem) unrootedChecked(absPath string, roots []string) (string, *WatchEventOutsideRootError) {
 	for _, root := range roots {
 		// Make sure the root ends with precisely one path separator, to
 		// ease prefix comparisons.
diff --git a/lib/fs/basicfs_xattr_unix.go b/lib/fs/basicfs_xattr_unix.go
index f43445c87..f32929708 100644
--- a/lib/fs/basicfs_xattr_unix.go
+++ b/lib/fs/basicfs_xattr_unix.go
@@ -69,7 +69,7 @@ var xattrBufPool = sync.Pool{
 }
 
 func getXattr(path, name string) ([]byte, error) {
-	buf := xattrBufPool.Get().([]byte)
+	buf := xattrBufPool.Get().([]byte) //nolint:forcetypeassert
 	defer func() {
 		// Put the buffer back in the pool, or not if we're not supposed to
 		// (we returned it to the caller).
diff --git a/lib/fs/casefs.go b/lib/fs/casefs.go
index d88ccc0a4..bf8ecb63b 100644
--- a/lib/fs/casefs.go
+++ b/lib/fs/casefs.go
@@ -24,16 +24,16 @@ const (
 	caseCacheItemLimit = 4 << 10
 )
 
-type ErrCaseConflict struct {
+type CaseConflictError struct {
 	Given, Real string
 }
 
-func (e *ErrCaseConflict) Error() string {
+func (e *CaseConflictError) Error() string {
 	return fmt.Sprintf(`remote "%v" uses different upper or lowercase characters than local "%v"; change the casing on either side to match the other`, e.Given, e.Real)
 }
 
 func IsErrCaseConflict(err error) bool {
-	e := &ErrCaseConflict{}
+	e := &CaseConflictError{}
 	return errors.As(err, &e)
 }
 
@@ -239,7 +239,7 @@ func (f *caseFilesystem) Rename(oldpath, newpath string) error {
 	}
 	if err := f.checkCase(newpath); err != nil {
 		// Case-only rename is ok
-		e := &ErrCaseConflict{}
+		e := &CaseConflictError{}
 		if !errors.As(err, &e) || e.Real != oldpath {
 			return err
 		}
@@ -389,7 +389,7 @@ func (f *caseFilesystem) checkCaseExisting(name string) error {
 	// comparing, as we don't want to treat a normalization difference as a
 	// case conflict.
 	if norm.NFC.String(realName) != norm.NFC.String(name) {
-		return &ErrCaseConflict{name, realName}
+		return &CaseConflictError{name, realName}
 	}
 	return nil
 }
diff --git a/lib/fs/fakefs.go b/lib/fs/fakefs.go
index af508f18c..3c056eab6 100644
--- a/lib/fs/fakefs.go
+++ b/lib/fs/fakefs.go
@@ -147,29 +147,29 @@ func newFakeFilesystem(rootURI string, _ ...Option) *fakeFS {
 		// *look* like file I/O, but they are not. Do not worry that they
 		// might fail.
 
-		rng := rand.New(rand.NewSource(int64(seed)))
+		rng := rand.New(rand.NewSource(int64(seed))) //nolint:gosec
 		var createdFiles int
 		var writtenData int64
 		for (files == 0 || createdFiles < files) && (maxsize == 0 || writtenData>>20 < int64(maxsize)) {
 			dir := filepath.Join(fmt.Sprintf("%02x", rng.Intn(255)), fmt.Sprintf("%02x", rng.Intn(255)))
 			file := fmt.Sprintf("%016x", rng.Int63())
-			fs.MkdirAll(dir, 0o755)
+			_ = fs.MkdirAll(dir, 0o755)
 
 			fd, _ := fs.Create(filepath.Join(dir, file))
 			createdFiles++
 
 			fsize := int64(sizeavg/2 + rng.Intn(sizeavg))
-			fd.Truncate(fsize)
+			_ = fd.Truncate(fsize)
 			writtenData += fsize
 
 			ftime := time.Unix(1000000000+rng.Int63n(10*365*86400), 0)
-			fs.Chtimes(filepath.Join(dir, file), ftime, ftime)
+			_ = fs.Chtimes(filepath.Join(dir, file), ftime, ftime)
 		}
 	}
 
 	if !nostfolder {
 		// Also create a default folder marker for good measure
-		fs.Mkdir(".stfolder", 0o700)
+		_ = fs.Mkdir(".stfolder", 0o700)
 	}
 
 	// We only set the latency after doing the operations required to create
@@ -284,9 +284,10 @@ func (fs *fakeFS) create(name string) (*fakeEntry, error) {
 	time.Sleep(fs.latency)
 
 	if entry := fs.entryForName(name); entry != nil {
-		if entry.entryType == fakeEntryTypeDir {
+		switch entry.entryType {
+		case fakeEntryTypeDir:
 			return nil, os.ErrExist
-		} else if entry.entryType == fakeEntryTypeSymlink {
+		case fakeEntryTypeSymlink:
 			return nil, errors.New("following symlink not supported")
 		}
 		entry.size = 0
@@ -731,6 +732,7 @@ func (fs *fakeFS) resetCounters() {
 }
 
 func (fs *fakeFS) reportMetricsPerOp(b *testing.B) {
+	b.Helper()
 	fs.reportMetricsPer(b, 1, "op")
 }
 
@@ -829,7 +831,7 @@ func (f *fakeFile) readShortAt(p []byte, offs int64) (int, error) {
 	if f.seed == 0 {
 		hf := fnv.New64()
 		hf.Write([]byte(f.name))
-		f.seed = int64(hf.Sum64())
+		f.seed = int64(hf.Sum64()) //nolint:gosec
 	}
 
 	// Check whether the read is a continuation of an RNG we already have or
@@ -839,14 +841,14 @@ func (f *fakeFile) readShortAt(p []byte, offs int64) (int, error) {
 	nextBlockOffs := (seedNo + 1) << randomBlockShift
 	if f.rng == nil || f.offset != offs || seedNo != f.seedOffs {
 		// This is not a straight read continuing from a previous one
-		f.rng = rand.New(rand.NewSource(f.seed + seedNo))
+		f.rng = rand.New(rand.NewSource(f.seed + seedNo)) //nolint:gosec
 
 		// If the read is not at the start of the block, discard data
 		// accordingly.
 		diff := offs - minOffs
 		if diff > 0 {
 			lr := io.LimitReader(f.rng, diff)
-			io.Copy(io.Discard, lr)
+			_, _ = io.Copy(io.Discard, lr)
 		}
 
 		f.offset = offs
diff --git a/lib/fs/filesystem.go b/lib/fs/filesystem.go
index fa34fe9fd..368ba1ca5 100644
--- a/lib/fs/filesystem.go
+++ b/lib/fs/filesystem.go
@@ -180,7 +180,7 @@ const (
 // SkipDir is used as a return value from WalkFuncs to indicate that
 // the directory named in the call is to be skipped. It is not returned
 // as an error by any function.
-var SkipDir = filepath.SkipDir
+var SkipDir = filepath.SkipDir //nolint:errname
 
 func IsExist(err error) bool {
 	return errors.Is(err, ErrExist)
@@ -259,15 +259,16 @@ func NewFilesystem(fsType FilesystemType, uri string, opts ...Option) Filesystem
 		// attributed to the calling function.
 		layersAboveWalkFilesystem++
 	}
-	if l.ShouldDebug("walkfs") {
+	switch {
+	case l.ShouldDebug("walkfs"):
 		// A walkFilesystem is not a layer to skip, it embeds the underlying
 		// filesystem, passing calls directly trough. Except for calls made
 		// during walking, however those are truly originating in the walk
 		// filesystem.
 		fs = NewWalkFilesystem(newLogFilesystem(fs, layersAboveWalkFilesystem))
-	} else if l.ShouldDebug("fs") {
+	case l.ShouldDebug("fs"):
 		fs = newLogFilesystem(NewWalkFilesystem(fs), layersAboveWalkFilesystem)
-	} else {
+	default:
 		fs = NewWalkFilesystem(fs)
 	}
 
diff --git a/lib/fs/filesystem_copy_range_standard.go b/lib/fs/filesystem_copy_range_standard.go
index cd49fafe0..f59e0fd64 100644
--- a/lib/fs/filesystem_copy_range_standard.go
+++ b/lib/fs/filesystem_copy_range_standard.go
@@ -7,6 +7,7 @@
 package fs
 
 import (
+	"errors"
 	"io"
 )
 
@@ -28,7 +29,7 @@ func copyRangeStandard(src, dst File, srcOffset, dstOffset, size int64) error {
 		}
 		n, err := src.ReadAt(buf, srcOffset)
 		if err != nil {
-			if err == io.EOF {
+			if errors.Is(err, io.EOF) {
 				return io.ErrUnexpectedEOF
 			}
 			return err
diff --git a/lib/fs/mtimefs.go b/lib/fs/mtimefs.go
index 3264e510c..523652d77 100644
--- a/lib/fs/mtimefs.go
+++ b/lib/fs/mtimefs.go
@@ -68,7 +68,7 @@ func (*optionMtime) String() string {
 
 func (f *mtimeFS) Chtimes(name string, atime, mtime time.Time) error {
 	// Do a normal Chtimes call, don't care if it succeeds or not.
-	f.chtimes(name, atime, mtime)
+	_ = f.chtimes(name, atime, mtime)
 
 	// Stat the file to see what happened. Here we *do* return an error,
 	// because it might be "does not exist" or similar.
diff --git a/lib/fs/types.go b/lib/fs/types.go
index 7dc86c9fb..224e24389 100644
--- a/lib/fs/types.go
+++ b/lib/fs/types.go
@@ -26,8 +26,10 @@ type Option interface {
 type FilesystemFactory func(string, ...Option) (Filesystem, error)
 
 // For each registered file system type, a function to construct a file system.
-var filesystemFactories map[FilesystemType]FilesystemFactory = make(map[FilesystemType]FilesystemFactory)
-var filesystemFactoriesMutex sync.Mutex = sync.Mutex{}
+var (
+	filesystemFactories      map[FilesystemType]FilesystemFactory = make(map[FilesystemType]FilesystemFactory)
+	filesystemFactoriesMutex sync.Mutex                           = sync.Mutex{}
+)
 
 // Register a function to be called when a filesystem is to be constructed with
 // the specified fsType. The function will receive the URI for the file system as well
diff --git a/lib/fs/util.go b/lib/fs/util.go
index 41ee39300..94a0a5416 100644
--- a/lib/fs/util.go
+++ b/lib/fs/util.go
@@ -192,7 +192,7 @@ func CommonPrefix(first, second string) string {
 	}
 
 	common := make([]string, 0, count)
-	for i := 0; i < count; i++ {
+	for i := range count {
 		if firstParts[i] != secondParts[i] {
 			break
 		}
diff --git a/lib/fs/walkfs.go b/lib/fs/walkfs.go
index 36bce97a7..a6c8613bb 100644
--- a/lib/fs/walkfs.go
+++ b/lib/fs/walkfs.go
@@ -89,7 +89,7 @@ func (f *walkFilesystem) walk(path string, info FileInfo, walkFn WalkFunc, ances
 
 	err = walkFn(path, info, nil)
 	if err != nil {
-		if info.IsDir() && err == SkipDir {
+		if info.IsDir() && errors.Is(err, SkipDir) {
 			return nil
 		}
 		return err
@@ -117,13 +117,13 @@ func (f *walkFilesystem) walk(path string, info FileInfo, walkFn WalkFunc, ances
 		filename := filepath.Join(path, name)
 		fileInfo, err := f.Lstat(filename)
 		if err != nil {
-			if err := walkFn(filename, fileInfo, err); err != nil && err != SkipDir {
+			if err := walkFn(filename, fileInfo, err); err != nil && !errors.Is(err, SkipDir) {
 				return err
 			}
 		} else {
 			err = f.walk(filename, fileInfo, walkFn, ancestors)
 			if err != nil {
-				if !fileInfo.IsDir() || err != SkipDir {
+				if !fileInfo.IsDir() || !errors.Is(err, SkipDir) {
 					return err
 				}
 			}
diff --git a/lib/model/folder.go b/lib/model/folder.go
index 0ebe3db3d..8d98e8495 100644
--- a/lib/model/folder.go
+++ b/lib/model/folder.go
@@ -1077,7 +1077,7 @@ func (f *folder) monitorWatch(ctx context.Context) {
 			f.setWatchError(err, next)
 			// This error was previously a panic and should never occur, so generate
 			// a warning, but don't do it repetitively.
-			var errOutside *fs.ErrWatchEventOutsideRoot
+			var errOutside *fs.WatchEventOutsideRootError
 			if errors.As(err, &errOutside) {
 				if !warnedOutside {
 					l.Warnln(err)
diff --git a/lib/model/folder_sendrecv.go b/lib/model/folder_sendrecv.go
index 2f659c2f0..ac84fd832 100644
--- a/lib/model/folder_sendrecv.go
+++ b/lib/model/folder_sendrecv.go
@@ -977,7 +977,7 @@ func (f *sendReceiveFolder) renameFile(cur, source, target protocol.FileInfo, db
 	}
 	switch stat, serr := f.mtimefs.Lstat(target.Name); {
 	case serr != nil:
-		var caseErr *fs.ErrCaseConflict
+		var caseErr *fs.CaseConflictError
 		switch {
 		case errors.As(serr, &caseErr):
 			if caseErr.Real != source.Name {
@@ -1149,7 +1149,7 @@ func (f *sendReceiveFolder) reuseBlocks(blocks []protocol.BlockInfo, reused []in
 	// reuse.
 	tempBlocks, err := scanner.HashFile(f.ctx, f.ID, f.mtimefs, tempName, file.BlockSize(), nil)
 	if err != nil {
-		var caseErr *fs.ErrCaseConflict
+		var caseErr *fs.CaseConflictError
 		if errors.As(err, &caseErr) {
 			if rerr := f.mtimefs.Rename(caseErr.Real, tempName); rerr == nil {
 				tempBlocks, err = scanner.HashFile(f.ctx, f.ID, f.mtimefs, tempName, file.BlockSize(), nil)
diff --git a/lib/model/folder_sendrecv_test.go b/lib/model/folder_sendrecv_test.go
index 822a567a4..5eff7a19c 100644
--- a/lib/model/folder_sendrecv_test.go
+++ b/lib/model/folder_sendrecv_test.go
@@ -1014,7 +1014,7 @@ func TestPullCaseOnlyPerformFinish(t *testing.T) {
 	default:
 	}
 
-	var caseErr *fs.ErrCaseConflict
+	var caseErr *fs.CaseConflictError
 	if !errors.As(err, &caseErr) {
 		t.Error("Expected case conflict error, got", err)
 	}