From b89f0dc94bd83857b187a84a0d4ae127000f0b1c Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Thu, 16 Jul 2026 20:47:57 +0200
Subject: fusefrontend: LockSharedStorage: loop on EINTR, add debug output

---
 internal/fusefrontend/file_lock.go | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

(limited to 'internal/fusefrontend')

diff --git a/internal/fusefrontend/file_lock.go b/internal/fusefrontend/file_lock.go
index f440754..c2965ae 100644
--- a/internal/fusefrontend/file_lock.go
+++ b/internal/fusefrontend/file_lock.go
@@ -4,6 +4,7 @@ import (
 	"golang.org/x/sys/unix"
 
 	"github.com/rfjakob/gocryptfs/v2/internal/syscallcompat"
+	"github.com/rfjakob/gocryptfs/v2/internal/tlog"
 )
 
 // SharedStorageLock conveniently wraps F_OFD_SETLKW.
@@ -17,7 +18,7 @@ import (
 // * unix.F_UNLCK (unlock)
 //
 // This function is a no-op if args.SharedStorage == false.
-func (f *File) LockSharedStorage(lkType int16, lkStart int64, lkLen int64) error {
+func (f *File) LockSharedStorage(lkType int16, lkStart int64, lkLen int64) (err error) {
 	if !f.rootNode.args.SharedStorage {
 		return nil
 	}
@@ -27,7 +28,21 @@ func (f *File) LockSharedStorage(lkType int16, lkStart int64, lkLen int64) error
 		Start:  lkStart,
 		Len:    lkLen,
 	}
-	return unix.FcntlFlock(uintptr(f.intFd()), syscallcompat.F_OFD_SETLKW, &lk)
+	err = unix.FcntlFlock(uintptr(f.intFd()), syscallcompat.F_OFD_SETLK, &lk)
+	switch err {
+	case unix.EACCES, unix.EAGAIN:
+		tlog.Debug.Printf("LockSharedStorage: waiting for lock")
+	case nil:
+		return
+	}
+	for {
+		err = unix.FcntlFlock(uintptr(f.intFd()), syscallcompat.F_OFD_SETLKW, &lk)
+		if err == unix.EINTR {
+			tlog.Debug.Printf("LockSharedStorage: looping on EINTR")
+			continue
+		}
+		return
+	}
 }
 
 // UnlockSharedStorage calls LockSharedStorage with unix.F_UNLCK.
-- 
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