opportunistically change ugid

src/access.cpp

@@ -74,10 +74,10 @@ namespace mergerfs
     access(const char *fusepath,
            int         mask)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _access(config.access,
                      config.srcmounts,

src/chmod.cpp

@@ -74,10 +74,10 @@ namespace mergerfs
     chmod(const char *fusepath,
           mode_t      mode)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _chmod(config.chmod,
                     config.srcmounts,

src/chown.cpp

@@ -78,10 +78,10 @@ namespace mergerfs
           uid_t       uid,
           gid_t       gid)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _chown(config.chown,
                     config.srcmounts,

src/create.cpp

@@ -40,6 +40,7 @@
 using std::string;
 using std::vector;
 using mergerfs::Policy;
+using namespace mergerfs::ugid;
 
 static
 int
@@ -69,7 +70,7 @@ _create(Policy::Func::Search  searchFunc,
 
   if(createpath[0] != existingpath[0])
     {
-      const mergerfs::ugid::SetResetGuard ugid(0,0);
+      const SuperUser superuser;
       fs::clonepath(existingpath[0],createpath[0],dirname);
     }
 
@@ -93,10 +94,10 @@ namespace mergerfs
            mode_t          mode,
            fuse_file_info *fileinfo)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _create(config.getattr,
                      config.create,

src/getattr.cpp

@@ -100,8 +100,8 @@ namespace mergerfs
       if(fusepath == config.controlfile)
         return _getattr_controlfile(*st);
 
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const ugid::Set         ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard readlock(&config.srcmountslock);
 
       return _getattr(config.getattr,
                       config.srcmounts,

src/getxattr.cpp

@@ -254,8 +254,8 @@ namespace mergerfs
                                      buf,
                                      count);
 
-      const ugid::SetResetGuard ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard   readlock(&config.srcmountslock);
+      const ugid::Set         ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard readlock(&config.srcmountslock);
 
       return _getxattr(config.getxattr,
                        config.srcmounts,

src/ioctl.cpp

@@ -98,10 +98,10 @@ _ioctl_dir(const string &fusepath,
            const int     cmd,
            void         *data)
 {
-  const fuse_context        *fc     = fuse_get_context();
-  const Config              &config = Config::get(fc);
-  const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-  const rwlock::ReadGuard    readlock(&config.srcmountslock);
+  const fuse_context      *fc     = fuse_get_context();
+  const Config            &config = Config::get(fc);
+  const ugid::Set          ugid(fc->uid,fc->gid);
+  const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
   return _ioctl_dir_base(config.getattr,
                          config.srcmounts,

src/link.cpp

@@ -38,6 +38,7 @@
 using std::string;
 using std::vector;
 using mergerfs::Policy;
+using namespace mergerfs::ugid;
 
 static
 int
@@ -64,7 +65,7 @@ _single_link(Policy::Func::Search  searchFunc,
         return -1;
 
       {
-        const mergerfs::ugid::SetResetGuard ugid(0,0);
+        const SuperUser superuser;
         fs::clonepath(foundpath[0],base,newpathdir);
       }
 
@@ -110,10 +111,10 @@ namespace mergerfs
     link(const char *from,
          const char *to)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _link(config.getattr,
                    config.link,

src/listxattr.cpp

@@ -115,8 +115,8 @@ namespace mergerfs
       if(fusepath == config.controlfile)
         return _listxattr_controlfile(list,size);
 
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const ugid::Set         ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard readlock(&config.srcmountslock);
 
       return _listxattr(config.listxattr,
                         config.srcmounts,

src/mkdir.cpp

@@ -39,6 +39,7 @@
 using std::string;
 using std::vector;
 using mergerfs::Policy;
+using namespace mergerfs::ugid;
 
 static
 int
@@ -72,7 +73,7 @@ _mkdir(Policy::Func::Search  searchFunc,
 
       if(createpath != existingpath[0])
         {
-          const mergerfs::ugid::SetResetGuard ugid(0,0);
+          const SuperUser superuser;
           fs::clonepath(existingpath[0],createpath,dirname);
         }
 
@@ -94,10 +95,10 @@ namespace mergerfs
     mkdir(const char *fusepath,
           mode_t      mode)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _mkdir(config.getattr,
                     config.mkdir,

src/mknod.cpp

@@ -41,6 +41,7 @@
 using std::string;
 using std::vector;
 using mergerfs::Policy;
+using namespace mergerfs::ugid;
 
 static
 int
@@ -74,7 +75,7 @@ _mknod(Policy::Func::Search  searchFunc,
 
       if(createpath != existingpath[0])
         {
-          const mergerfs::ugid::SetResetGuard ugid(0,0);
+          const SuperUser superuser;
           fs::clonepath(existingpath[0],createpath,dirname);
         }
 
@@ -97,10 +98,10 @@ namespace mergerfs
           mode_t      mode,
           dev_t       rdev)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _mknod(config.getattr,
                     config.mknod,

src/open.cpp

@@ -76,10 +76,10 @@ namespace mergerfs
     open(const char     *fusepath,
          fuse_file_info *fileinfo)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _open(config.open,
                    config.srcmounts,

src/readdir.cpp

@@ -96,10 +96,10 @@ namespace mergerfs
             off_t            offset,
             fuse_file_info  *fi)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _readdir(config.srcmounts,
                       fusepath,

src/readlink.cpp

@@ -75,10 +75,10 @@ namespace mergerfs
              char       *buf,
              size_t      size)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _readlink(config.readlink,
                        config.srcmounts,

src/removexattr.cpp

@@ -87,8 +87,8 @@ namespace mergerfs
       if(fusepath == config.controlfile)
         return -ENOTSUP;
 
-      const ugid::SetResetGuard ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard   readlock(&config.srcmountslock);
+      const ugid::Set         ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard readlock(&config.srcmountslock);
 
       return _removexattr(config.removexattr,
                           config.srcmounts,

src/rename.cpp

@@ -39,6 +39,7 @@
 using std::string;
 using std::vector;
 using mergerfs::Policy;
+using namespace mergerfs::ugid;
 
 static
 int
@@ -64,7 +65,7 @@ _single_rename(Policy::Func::Search  searchFunc,
         return -1;
 
       {
-        const mergerfs::ugid::SetResetGuard ugid(0,0);
+        const SuperUser superuser;
         fs::clonepath(newpathdir[0],oldbasepath,dirname);
       }
 
@@ -113,10 +114,10 @@ namespace mergerfs
     rename(const char *oldpath,
            const char *newpath)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _rename(config.getattr,
                      config.rename,

src/rmdir.cpp

@@ -73,10 +73,10 @@ namespace mergerfs
     int
     rmdir(const char *fusepath)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readguard(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readguard(&config.srcmountslock);
 
       return _rmdir(config.rmdir,
                     config.srcmounts,

src/setxattr.cpp

@@ -321,8 +321,8 @@ namespace mergerfs
                                        flags);
         }
 
-      const ugid::SetResetGuard ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard   readlock(&config.srcmountslock);
+      const ugid::Set         ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard readlock(&config.srcmountslock);
 
       return _setxattr(config.setxattr,
                        config.srcmounts,

src/statfs.cpp

@@ -124,10 +124,10 @@ namespace mergerfs
     statfs(const char     *fusepath,
            struct statvfs *stat)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _statfs(config.srcmounts,
                      *stat);

src/symlink.cpp

@@ -77,10 +77,10 @@ namespace mergerfs
     symlink(const char *oldpath,
             const char *newpath)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _symlink(config.symlink,
                       config.srcmounts,

src/truncate.cpp

@@ -77,10 +77,10 @@ namespace mergerfs
     truncate(const char *fusepath,
              off_t       size)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _truncate(config.truncate,
                        config.srcmounts,

src/ugid.cpp

@@ -25,7 +25,16 @@
 #include "ugid.hpp"
 
 #if defined __linux__
+__thread uid_t mergerfs::ugid::currentuid  = 0;
+__thread gid_t mergerfs::ugid::currentgid  = 0;
+__thread bool  mergerfs::ugid::initialized = false;
 #elif defined __APPLE__
+__thread uid_t mergerfs::ugid::currentuid  = 0;
+__thread gid_t mergerfs::ugid::currentgid  = 0;
+__thread bool  mergerfs::ugid::initialized = false;
 #else
-pthread_mutex_t mergerfs::ugid::SetResetGuard::lock = PTHREAD_MUTEX_INITIALIZER;
+uid_t           mergerfs::ugid::currentuid  = 0;
+gid_t           mergerfs::ugid::currentgid  = 0;
+bool            mergerfs::ugid::initialized = false;
+pthread_mutex_t mergerfs::ugid::lock        = PTHREAD_MUTEX_INITIALIZER;
 #endif

src/ugid_linux.hpp

@@ -27,38 +27,89 @@
 #include <unistd.h>
 #include <sys/syscall.h>
 
+#define ROOT 0
+#define UNCHANGED -1
+
 namespace mergerfs
 {
   namespace ugid
   {
-    struct SetResetGuard
+    extern __thread uid_t currentuid;
+    extern __thread gid_t currentgid;
+    extern __thread bool  initialized;
+
+    static
+    void
+    init()
+    {
+      if(initialized == false)
+        {
+          currentuid  = ::syscall(SYS_geteuid);
+          currentgid  = ::syscall(SYS_getegid);
+          initialized = true;
+        }
+    }
+
+    static
+    void
+    set(const uid_t newuid,
+        const gid_t newgid)
+    {
+      if(currentuid != newuid || currentgid != newgid)
+        {
+          ::syscall(SYS_setreuid,UNCHANGED,ROOT);
+          if(currentgid != newgid)
+            ::syscall(SYS_setregid,UNCHANGED,newgid);
+          if(newuid != ROOT)
+            ::syscall(SYS_setreuid,UNCHANGED,newuid);
+          currentuid = newuid;
+          currentgid = newgid;
+        }
+    }
+
+    struct SetReset
     {
-      SetResetGuard(const uid_t _newuid,
-                    const gid_t _newgid)
+      SetReset(const uid_t newuid,
+               const gid_t newgid)
       {
-        olduid = ::syscall(SYS_geteuid);
-        oldgid = ::syscall(SYS_getegid);
-        newuid = _newuid;
-        newgid = _newgid;
-
-        if(newgid != oldgid)
-          ::syscall(SYS_setregid,-1,newgid);
-        if(newuid != olduid)
-          ::syscall(SYS_setreuid,-1,newuid);
+        init();
+
+        olduid = currentuid;
+        oldgid = currentgid;
+
+        set(newuid,newgid);
       }
 
-      ~SetResetGuard()
+      ~SetReset()
       {
-        if(olduid != newuid)
-          ::syscall(SYS_setreuid,-1,olduid);
-        if(oldgid != newgid)
-          ::syscall(SYS_setregid,-1,oldgid);
+        set(olduid,oldgid);
       }
 
-      uid_t  olduid;
-      gid_t  oldgid;
-      uid_t  newuid;
-      gid_t  newgid;
+      uid_t olduid;
+      gid_t oldgid;
+    };
+
+    struct SuperUser
+    {
+      SuperUser()
+        : setreset(0,0)
+      {}
+
+      const SetReset setreset;
+    };
+
+    struct Set
+    {
+      Set(const uid_t newuid,
+          const gid_t newgid)
+      {
+        init();
+
+        set(newuid,newgid);
+      }
     };
   }
 }
+
+#undef ROOT
+#undef UNCHANGED

src/ugid_mutex.hpp

@@ -31,38 +31,68 @@ namespace mergerfs
 {
   namespace ugid
   {
-    struct SetResetGuard
+    extern uid_t currentuid;
+    extern gid_t currentgid;
+    extern bool  initialized;
+    extern pthread_mutex_t lock;
+
+    static
+    void
+    init()
+    {
+      if(initialized == false)
+        {
+          currentuid  = ::geteuid();
+          currentgid  = ::getegid();
+          initialized = true;
+        }
+    }
+
+    static
+    void
+    set(const uid_t newuid,
+        const gid_t newgid)
+    {
+
+    }
+
+    struct SetReset
     {
-      SetResetGuard(const uid_t _newuid,
-                    const gid_t _newgid)
+      SetReset(const uid_t _newuid,
+               const gid_t _newgid)
       {
-        pthread_mutex_lock(&lock);
+        init();
 
-        olduid   = ::geteuid();
-        oldgid   = ::getegid();
-        newuid   = _newuid;
-        newgid   = _newgid;
+        olduid = currentuid;
+        oldgid = currentgid;
 
-        if(newgid != oldgid)
+        seteuid(0);
+        if(_newgid != oldgid)
           setegid(newgid);
-        if(newuid != olduid)
+        if(_newuid != olduid)
           seteuid(newuid);
       }
 
       ~SetResetGuard()
       {
         if(olduid != newuid)
-          seteuid(newuid);
+          seteuid(olduid);
         if(oldgid != newgid)
-          setegid(newgid);
+          setegid(oldgid);
       }
 
       uid_t  olduid;
       gid_t  oldgid;
       uid_t  newuid;
       gid_t  newgid;
+    };
 
-      static pthread_mutex_t lock;
+    struct SuperUser : public SetReset
+    {
+      SuperUser()
+        : UnlockedSetReset(0,0)
+      {}
     };
+
   }
 }

src/ugid_osx.hpp

@@ -29,29 +29,75 @@ namespace mergerfs
 {
   namespace ugid
   {
-    struct SetResetGuard
+    extern __thread uid_t currentuid;
+    extern __thread gid_t currentgid;
+    extern __thread bool  initialized;
+
+    static
+    void
+    init()
     {
-      SetResetGuard(const uid_t _newuid,
-                    const gid_t _newgid)
-      {
-        pthread_getugid_np(&olduid,&oldgid);
-        newuid   = _newuid;
-        newgid   = _newgid;
+      if(initialized == false)
+        {
+          pthread_getugid_np(&currentuid,&currentgid);
+          initialized = true;
+        }
+    }
 
-        if(newgid != oldgid || newuid != olduid)
+    static
+    void
+    set(const uid_t newuid,
+        const gid_t newgid)
+    {
+      if(currentuid != newuid || currentgid != newgid)
+        {
+          pthread_setugid_np(KAUTH_UID_NONE,KAUTH_GID_NONE);
           pthread_setugid_np(newuid,newgid);
+          currentuid = newuid;
+          currentgid = newgid;
+        }
+    }
+
+    struct SetReset
+    {
+      SetReset(const uid_t newuid,
+               const gid_t newgid)
+      {
+        init();
+
+        olduid = currentuid;
+        oldgid = currentgid;
+
+        set(newuid,newgid);
       }
 
-      ~SetResetGuard()
+      ~SetReset()
       {
-        if(newgid != oldgid || newuid != olduid)
-          pthread_setugid_np(newuid,newgid);
+        set(olduid,oldgid);
       }
 
-      uid_t  olduid;
-      gid_t  oldgid;
-      uid_t  newuid;
-      gid_t  newgid;
+      uid_t olduid;
+      gid_t oldgid;
+    };
+
+    struct SuperUser
+    {
+      SuperUser()
+        : setreset(0,0)
+      {}
+
+      SetReset setreset;
+    };
+
+    struct Set
+    {
+      Set(const uid_t newuid,
+          const gid_t newgid)
+      {
+        init();
+
+        set(newuid,newgid);
+      }
     };
   }
 }

src/unlink.cpp

@@ -74,10 +74,10 @@ namespace mergerfs
     int
     unlink(const char *fusepath)
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _unlink(config.unlink,
                      config.srcmounts,

src/utimens.cpp

@@ -77,10 +77,10 @@ namespace mergerfs
     utimens(const char     *fusepath,
             const timespec  ts[2])
     {
-      const fuse_context        *fc     = fuse_get_context();
-      const Config              &config = Config::get(fc);
-      const ugid::SetResetGuard  ugid(fc->uid,fc->gid);
-      const rwlock::ReadGuard    readlock(&config.srcmountslock);
+      const fuse_context      *fc     = fuse_get_context();
+      const Config            &config = Config::get(fc);
+      const ugid::Set          ugid(fc->uid,fc->gid);
+      const rwlock::ReadGuard  readlock(&config.srcmountslock);
 
       return _utimens(config.utimens,
                       config.srcmounts,