diff --git a/include/minigui.h b/include/minigui.h
index 58d394a9..3290b356 100644
--- a/include/minigui.h
+++ b/include/minigui.h
@@ -1222,9 +1222,6 @@ typedef struct _ZNODEHEADER {
     int             lock_count;
 
 #ifdef _MGSCHEMA_COMPOSITING
-    /** The file descriptor of the surface; since 5.2.0. */
-    int             fd;
-
     /** The count for changes of the content. */
     unsigned int    changes;
     /**
diff --git a/src/gui/window.c b/src/gui/window.c
index b2d93660..556a6330 100644
--- a/src/gui/window.c
+++ b/src/gui/window.c
@@ -4478,8 +4478,8 @@ HWND GUIAPI CreateMainWindowEx2 (PMAINWINCREATE pCreateInfo, LINT id,
 #ifdef _MGSCHEMA_COMPOSITING
     /* Since 5.2.0: keep fd available. */
     if (0 && pWin->surf->shared_header) {
-        close (pWin->surf->shared_header->fd);
-        pWin->surf->shared_header->fd = -1;
+        close (pWin->surf->fd);
+        pWin->surf->fd = -1;
     }
 #endif
 
@@ -6038,8 +6038,8 @@ HWND GUIAPI CreateWindowEx2 (const char* spClassName,
 #ifdef _MGSCHEMA_COMPOSITING
     /* Since 5.2.0: keep fd available. */
     if (0 && dwExStyle & WS_EX_CTRLASMAINWIN && pNewCtrl->surf->shared_header) {
-        close (pNewCtrl->surf->shared_header->fd);
-        pNewCtrl->surf->shared_header->fd = -1;
+        close (pNewCtrl->surf->fd);
+        pNewCtrl->surf->fd = -1;
     }
 #endif
 
@@ -6081,7 +6081,7 @@ int GUIAPI GetWindowSharedSurfaceFD (HWND hWnd, size_t *map_size, DWORD *flags)
                 *flags |= MEMDC_FLAG_HWSURFACE;
         }
 
-        return pWin->surf->shared_header->fd;
+        return pWin->surf->fd;
     }
 
     return -1;
diff --git a/src/include/dc.h b/src/include/dc.h
index 52279879..c0291322 100644
--- a/src/include/dc.h
+++ b/src/include/dc.h
@@ -521,14 +521,16 @@ static inline void _dc_step_y (PDC pdc, int step)
 
 #       define BLOCK_DRAW_SEM(pdc)                                  \
 do {                                                                \
-    if (pdc->surface->shared_header)                                \
-        LOCK_SURFACE_SEM (pdc->surface->shared_header->sem_num);    \
+    if (pdc->surface->shared_header) {                              \
+        __mg_lock_file_for_write(pdc->surface->fd);                 \
+    }                                                               \
 } while (0)
 
 #       define UNBLOCK_DRAW_SEM(pdc)                                \
 do {                                                                \
-    if (pdc->surface->shared_header)                                \
-        UNLOCK_SURFACE_SEM (pdc->surface->shared_header->sem_num);  \
+    if (pdc->surface->shared_header) {                              \
+        __mg_unlock_file_for_write(pdc->surface->fd);               \
+    }                                                               \
 } while (0)
 
 #       define IS_SCREEN_SURFACE(pdc)                       \
diff --git a/src/include/drawsemop.h b/src/include/drawsemop.h
index 052bcd1f..907ee068 100644
--- a/src/include/drawsemop.h
+++ b/src/include/drawsemop.h
@@ -51,12 +51,10 @@
 #ifndef GUI_DRAWSEMOP_H
     #define GUI_DRAWSEMOP_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif  /* __cplusplus */
-
 #include <errno.h>
 
+#include "misc.h"
+
 static inline void my_sem_op (int semid, int num, int op)
 {
     struct sembuf sb;
@@ -70,6 +68,9 @@ again:
         if (errno == EINTR) {
             goto again;
         }
+        else {
+            _ERR_PRINTF("Failed semop: %m\n");
+        }
     }
 }
 
@@ -79,9 +80,21 @@ again:
 #define LOCK_SCREEN_SEM()   my_sem_op(SHAREDRES_SEMID, _IDX_SEM_SCR, -1)
 #define UNLOCK_SCREEN_SEM() my_sem_op(SHAREDRES_SEMID, _IDX_SEM_SCR, 1)
 
+extern int __mg_client_id;
+
+#if 0
 #ifdef _MGSCHEMA_COMPOSITING
-#   define LOCK_SURFACE_SEM(num)    my_sem_op(SHAREDRES_SEMID_SHARED_SURF, num, -1)
-#   define UNLOCK_SURFACE_SEM(num)  my_sem_op(SHAREDRES_SEMID_SHARED_SURF, num, 1)
+#   define LOCK_SURFACE_SEM(num)    \
+    do {  \
+        printf("Locking semaphor %d for client: %d\n", num, __mg_client_id);   \
+        my_sem_op(SHAREDRES_SEMID_SHARED_SURF, num, -1); \
+    } while (0)
+#   define UNLOCK_SURFACE_SEM(num)  \
+    do { \
+        my_sem_op(SHAREDRES_SEMID_SHARED_SURF, num, 1); \
+        printf("Unlocked semaphor %d for client: %d\n", num, __mg_client_id);   \
+    } while (0)
+#endif
 #endif
 
 #ifdef _MGHAVE_CURSOR
@@ -157,6 +170,10 @@ again:
 #   define UNLOCK_MOUSEMOVE_SEM()   my_sem_op(SHAREDRES_SEMID, _IDX_SEM_MOUSEMOVE, 1)
 #endif /* _MGRM_PROCESSES */
 
+#ifdef __cplusplus
+extern "C" {
+#endif  /* __cplusplus */
+
 #ifdef __cplusplus
 }
 #endif  /* __cplusplus */
diff --git a/src/include/misc.h b/src/include/misc.h
index 99b5af04..4bf2a604 100644
--- a/src/include/misc.h
+++ b/src/include/misc.h
@@ -79,6 +79,11 @@ struct timezone {
 extern "C" {
 #endif  /* __cplusplus */
 
+void __mg_lock_file_for_read(int fd);
+void __mg_unlock_file_for_read(int fd);
+void __mg_lock_file_for_write(int fd);
+void __mg_unlock_file_for_write(int fd);
+
 unsigned int __mg_os_get_random_seed (void);
 void __mg_os_time_delay (int ms);
 void __mg_os_start_time (void);
diff --git a/src/include/newgal.h b/src/include/newgal.h
index 9ef1145e..70f05d59 100644
--- a/src/include/newgal.h
+++ b/src/include/newgal.h
@@ -145,20 +145,19 @@ typedef struct _SharedSurfaceHeader {
     /* The client identifier of the creator. */
     int             create_cli;
 
-    /* The number of semphore for this surface.
-       The SysV semaphore set id for synchronizing this shared surface:
-       SHAREDRES_SEMID_SHARED_SURF. */
-    int             sem_num;
-
-    /* the size of the whole buffer */
-    size_t          map_size;
-    /* the offset of pixels data */
-    off_t           pixels_off;
-
-    /* The file descriptor in context of the creator. */
-    int             fd;
     /* Not zero for hardware surface. */
     int             byhw;
+
+    /* Deprecated since 5.2.0.
+       The number of semphore for this surface.
+       The SysV semaphore set id for synchronizing this shared surface:
+       SHAREDRES_SEMID_SHARED_SURF.
+    int             sem_num; */
+
+    /* Deprecated since 5.2.0.
+       The file descriptor in context of the creator.
+    int             fd; */
+
     /* the size of the surface */
     int             width, height;
     /* the pitch of the surface */
@@ -168,6 +167,11 @@ typedef struct _SharedSurfaceHeader {
     /* the RGBA masks */
     Uint32          Rmask, Gmask, Bmask, Amask;
 
+    /* the size of the whole buffer */
+    size_t          map_size;
+    /* the offset of pixels data */
+    off_t           pixels_off;
+
     /* The dirty information */
     GAL_DirtyInfo   dirty_info;
 } GAL_SharedSurfaceHeader;
@@ -234,6 +238,8 @@ typedef struct GAL_Surface {
     GAL_SharedSurfaceHeader *shared_header;     /* Private */
     /* The dirty info for non-shared surface. */
     GAL_DirtyInfo *dirty_info;                  /* Private */
+    /* The file descriptor if the surface is a shared surface. */
+    int  fd;                                    /* Private; since 5.2.0. */
 #endif
 } GAL_Surface;
 
diff --git a/src/include/zorder.h b/src/include/zorder.h
index 4d33c0c2..0e22920d 100644
--- a/src/include/zorder.h
+++ b/src/include/zorder.h
@@ -79,7 +79,6 @@ typedef struct _ZORDERNODE {
     unsigned int    lock_count;     /* the lock count */
 
 #ifdef _MGSCHEMA_COMPOSITING
-    int             fd;             /* the file descriptor; since 5.2.0. */
     unsigned int    changes;        /* count for changes of content */
     int             ct;             /* the compositing type */
     DWORD           ct_arg;         /* the argument for compositing */
diff --git a/src/kernel/compsor-manager.c b/src/kernel/compsor-manager.c
index 000381d2..81b0c1d9 100644
--- a/src/kernel/compsor-manager.c
+++ b/src/kernel/compsor-manager.c
@@ -56,7 +56,6 @@
 #include <string.h>
 #include <errno.h>
 
-#define _DEBUG
 #include "common.h"
 
 #if defined(_MGRM_PROCESSES) && defined(_MGSCHEMA_COMPOSITING)
@@ -131,9 +130,10 @@ static const CompositorOps* load_default_compositor (void)
 
 static void lock_znode_surface (PDC pdc, ZORDERNODE* node)
 {
+    _DBG_PRINTF("lock count for node %p: %d\n", node, node->lock_count);
     if (node->lock_count == 0) {
         if (pdc->surface->shared_header) {
-            LOCK_SURFACE_SEM (pdc->surface->shared_header->sem_num);
+            __mg_lock_file_for_read(pdc->surface->fd);
         }
 
         node->dirty_age = pdc->surface->dirty_info->dirty_age;
@@ -147,11 +147,13 @@ static void lock_znode_surface (PDC pdc, ZORDERNODE* node)
 
 static void unlock_znode_surface (PDC pdc, ZORDERNODE* node)
 {
+    _DBG_PRINTF("lock count for node %p: %d\n", node, node->lock_count);
     if (node->lock_count > 0) {
         node->lock_count--;
         if (node->lock_count == 0) {
-            if (pdc->surface->shared_header)
-                UNLOCK_SURFACE_SEM (pdc->surface->shared_header->sem_num);
+            if (pdc->surface->shared_header) {
+                __mg_unlock_file_for_read(pdc->surface->fd);
+            }
 
             node->dirty_age = 0;
             node->nr_dirty_rcs = 0;
diff --git a/src/kernel/desktop-procs.c b/src/kernel/desktop-procs.c
index b72e36db..21988d4d 100644
--- a/src/kernel/desktop-procs.c
+++ b/src/kernel/desktop-procs.c
@@ -365,7 +365,7 @@ static intptr_t cliAllocZOrderNode (PMAINWIN pWin, const COMPOSITINGINFO* ct_inf
     }
 
     if (ClientRequestEx2 (&req, caption, strlen(caption) + 1,
-            pWin->surf->shared_header->fd,
+            pWin->surf->fd,
             &ret, sizeof (intptr_t), NULL) < 0)
         return -1;
 #else   /* ndef _MGSCHEMA_COMPOSITING */
@@ -524,7 +524,7 @@ static intptr_t cliStartTrackPopupMenu (PTRACKMENUINFO ptmi)
 
         info.surf_flags = surf->flags;
         info.surf_size = surf->shared_header->map_size;
-        if (ClientRequestEx2 (&req, NULL, 0, surf->shared_header->fd,
+        if (ClientRequestEx2 (&req, NULL, 0, surf->fd,
                 &ret, sizeof (intptr_t), NULL) < 0)
             return -1;
     }
@@ -2211,7 +2211,7 @@ static int resize_window_surface (PMAINWIN pWin, const RECT* prcResult)
 
         pWin->surf = new_surf;
         if (pWin->surf->shared_header)
-            return pWin->surf->shared_header->fd;
+            return pWin->surf->fd;
         else
             return 0;
     }
@@ -2257,9 +2257,9 @@ static int dskMoveGlobalControl (PMAINWIN pCtrl, RECT* prcExpect)
 
 #ifdef _MGSCHEMA_COMPOSITING
     /* Since 5.2.0: keep fd available. */
-    if (0 && pCtrl->surf->shared_header && pCtrl->surf->shared_header->fd >= 0) {
-        close (pCtrl->surf->shared_header->fd);
-        pCtrl->surf->shared_header->fd = -1;
+    if (0 && pCtrl->surf->shared_header && pCtrl->surf->fd >= 0) {
+        close (pCtrl->surf->fd);
+        pCtrl->surf->fd = -1;
     }
 #endif
 
@@ -2289,9 +2289,9 @@ static int dskMoveMainWindow (PMAINWIN pWin, RECT* prcExpect)
     }
 
     /* Since 5.2.0: keep fd available. */
-    if (0 && pWin->surf->shared_header && pWin->surf->shared_header->fd >= 0) {
-        close (pWin->surf->shared_header->fd);
-        pWin->surf->shared_header->fd = -1;
+    if (0 && pWin->surf->shared_header && pWin->surf->fd >= 0) {
+        close (pWin->surf->fd);
+        pWin->surf->fd = -1;
     }
 #endif
 
diff --git a/src/kernel/desktop.c b/src/kernel/desktop.c
index b451ced3..867f199c 100644
--- a/src/kernel/desktop.c
+++ b/src/kernel/desktop.c
@@ -1535,10 +1535,6 @@ static int srvForceCloseMenu (int cli)
     for (i = (zi->nr_popupmenus - 1); i >= 0; i--) {
         DO_COMPSOR_OP_ARGS (on_hiding_ppp, i);
         DeleteMemDC (menu_nodes[i].mem_dc);
-        /* Since 5.2.0 */
-        assert (menu_nodes[i].fd >= 0);
-        close (menu_nodes[i].fd);
-        menu_nodes[i].fd = -1;
     }
 #endif  /* defined _MGSCHEMA_COMPOSITING */
 
@@ -1653,7 +1649,6 @@ static int srvStartTrackPopupMenu (int cli, const RECT* rc, HWND ptmi,
     menu_nodes [zi->nr_popupmenus].rc = *rc;
     menu_nodes [zi->nr_popupmenus].hwnd = ptmi;
 #ifdef _MGSCHEMA_COMPOSITING
-    menu_nodes [zi->nr_popupmenus].fd = fd;
     menu_nodes [zi->nr_popupmenus].changes = 0;
     menu_nodes [zi->nr_popupmenus].ct = CT_OPAQUE;
     menu_nodes [zi->nr_popupmenus].ct_arg = 0;
@@ -1699,8 +1694,6 @@ static int srvEndTrackPopupMenu (int cli, int idx_znode)
 
 #ifdef _MGSCHEMA_COMPOSITING
     DO_COMPSOR_OP_ARGS (on_hiding_ppp, idx_znode);
-    close(menu_nodes [idx_znode].fd);
-    menu_nodes [idx_znode].fd = -1;
     DeleteMemDC (menu_nodes [idx_znode].mem_dc);
 #else   /* not defined _MGSCHEMA_COMPOSITING */
     rc = menu_nodes [idx_znode].rc;
@@ -2361,7 +2354,6 @@ static int AllocZOrderNodeEx (ZORDERINFO* zi, int cli, HWND hwnd, HWND main_win,
     nodes [free_slot].main_win = main_win;
     nodes [free_slot].lock_count = 0;
 #ifdef _MGSCHEMA_COMPOSITING
-    nodes [free_slot].fd = fd;
     nodes [free_slot].changes = 0;
     nodes [free_slot].ct = validate_compositing_type (flags, ct);
     nodes [free_slot].ct_arg = ct_arg;
@@ -2577,14 +2569,6 @@ static int FreeZOrderNodeEx (ZORDERINFO* zi, int idx_znode, HDC* memdc)
         nodes[idx_znode].caption = NULL;
     }
 
-#ifdef _MGSCHEMA_COMPOSITING
-    /* Since 5.2.0 */
-    if (nodes[idx_znode].fd >= 0) {
-        close(nodes[idx_znode].fd);
-        nodes[idx_znode].fd = -1;
-    }
-#endif
-
     /* Free mask rects */
     if (nodes[idx_znode].idx_mask_rect) {
         release_znode_maskrect (nodes, idx_znode);
@@ -3728,10 +3712,6 @@ static int dskMoveWindow (int cli, int idx_znode, HDC memdc, int fd,
         if (memdc != HDC_INVALID) {
             DeleteMemDC (nodes [idx_znode].mem_dc);
             nodes [idx_znode].mem_dc = memdc;
-            /* Since 5.2.0 */
-            assert (nodes [idx_znode].fd >= 0);
-            close (nodes [idx_znode].fd);
-            nodes [idx_znode].fd = fd;
         }
 
         unlock_zi_for_change (zi);
diff --git a/src/misc/Makefile.am b/src/misc/Makefile.am
index 9a0dff38..245daa28 100644
--- a/src/misc/Makefile.am
+++ b/src/misc/Makefile.am
@@ -7,7 +7,7 @@ EXTRA_DIST= misc.c systext.c rwops.c endianrw.c nposix.c clipboard.c \
 
 libmisc_la_SOURCES = misc.c systext.c rwops.c endianrw.c nposix.c clipboard.c \
                 math.c about.c license.c anon_file.c rbtree.c map.c \
-                error.c sockio.c
+                error.c sockio.c lock_file.c
 
 SRC_FILES = $(libmisc_la_SOURCES)
 LIB_NAME=libmisc
diff --git a/src/newgal/surface-shared.c b/src/newgal/surface-shared.c
index 9346c515..95a31628 100644
--- a/src/newgal/surface-shared.c
+++ b/src/newgal/surface-shared.c
@@ -15,7 +15,7 @@
  *   and Graphics User Interface (GUI) support system for embedded systems
  *   and smart IoT devices.
  *
- *   Copyright (C) 2002~2020, Beijing FMSoft Technologies Co., Ltd.
+ *   Copyright (C) 2002~2023, Beijing FMSoft Technologies Co., Ltd.
  *   Copyright (C) 1998~2002, WEI Yongming
  *
  *   This program is free software: you can redistribute it and/or modify
@@ -143,6 +143,7 @@ GAL_Surface *GAL_CreateSharedRGBSurface (GAL_VideoDevice *video,
 #endif
     surface->shared_header = NULL;
     surface->dirty_info = NULL;
+    surface->fd = -1;
     GAL_SetClipRect (surface, NULL);
 
 #ifdef _MGUSE_UPDATE_REGION
@@ -202,10 +203,12 @@ GAL_Surface *GAL_CreateSharedRGBSurface (GAL_VideoDevice *video,
             surface->shared_header = hdr = (GAL_SharedSurfaceHeader*)data_map;
         }
 
+        surface->fd = fd;   /* Since 5.2.0 */
+
         /* fill fileds of shared header */
         memset (hdr, 0, sizeof(GAL_SharedSurfaceHeader));
         hdr->create_cli = __mg_client_id;
-        hdr->fd         = fd;
+        // hdr->fd         = fd;
         hdr->byhw       = byhw;
         hdr->width      = surface->w;
         hdr->height     = surface->h;
@@ -222,7 +225,8 @@ GAL_Surface *GAL_CreateSharedRGBSurface (GAL_VideoDevice *video,
         surface->dirty_info->dirty_age       = 0;
         surface->dirty_info->nr_dirty_rcs    = 0;
 
-        /* allocate semaphore from semaphore for shared surface */
+        /* Deprecated since 5.2.0.
+           allocate semaphore from semaphore for shared surface
         if (IsServer() && __gal_fake_screen == NULL) {
             // use 0 for wallpaper pattern,
             // because the semaphore set manager is not ready.
@@ -233,7 +237,7 @@ GAL_Surface *GAL_CreateSharedRGBSurface (GAL_VideoDevice *video,
             if (hdr->sem_num < 0) {
                 goto error;
             }
-        }
+        } */
 
         surface->pixels = (uint8_t*)surface->shared_header + pixels_off;
 
@@ -255,16 +259,16 @@ GAL_Surface *GAL_CreateSharedRGBSurface (GAL_VideoDevice *video,
 
 error:
     if (surface) {
-        if (surface->shared_header) {
-#if 0
-            if (sem_inited) {
-                sem_destroy (&surface->shared_header->sem_lock);
-            }
-#endif
+        if (surface->fd >= 0) {
+            close(surface->fd);
+            surface->fd = -1;
+        }
 
+        if (surface->shared_header) {
+            /* Deprecated since 5.2.0
             if (surface->shared_header->sem_num >= 0) {
                 __mg_free_sem_for_shared_surf (surface->shared_header->sem_num);
-            }
+            } */
 
             if (surface->shared_header->byhw) {
                 assert(video->FreeSharedHWSurface);
@@ -272,7 +276,6 @@ error:
                 surface->hwdata = NULL; /* set to NULL for GAL_FreeSurface */
             }
             else {
-                close (surface->shared_header->fd);
                 munmap (surface->shared_header,
                     surface->shared_header->map_size);
             }
@@ -301,20 +304,16 @@ void GAL_FreeSharedSurfaceData (GAL_Surface *surface)
     GAL_VideoDevice *video = surface->video;
 
     assert (surface->shared_header);
+    assert (surface->fd >= 0);
 
 #if 0
     sem_destroy (&surface->shared_header->sem_lock);
 #endif
 
+    /* Deprecated since 5.2.0
     if (surface->shared_header->sem_num >= 0) {
         __mg_free_sem_for_shared_surf (surface->shared_header->sem_num);
-    }
-
-    // the file descriptor may have been closed.
-    if (surface->shared_header->fd >= 0) {
-        close (surface->shared_header->fd);
-        surface->shared_header->fd = -1;
-    }
+    } */
 
     if (surface->shared_header->byhw) {
         assert (video->FreeSharedHWSurface);
@@ -326,6 +325,8 @@ void GAL_FreeSharedSurfaceData (GAL_Surface *surface)
             surface->shared_header->map_size);
     }
 
+    close(surface->fd);
+
     surface->pixels = NULL;
 #ifdef _MGUSE_PIXMAN
     surface->pix_img = NULL;
@@ -333,6 +334,7 @@ void GAL_FreeSharedSurfaceData (GAL_Surface *surface)
 #endif
     surface->shared_header = NULL;
     surface->dirty_info = NULL;
+    surface->fd = -1;
 }
 
 /*
@@ -373,6 +375,8 @@ GAL_Surface * GAL_AttachSharedRGBSurface (GAL_VideoDevice *video,
 
     surface->shared_header = NULL;
     surface->hwdata = NULL;
+    surface->fd = fd;
+
     if (video && video->AttachSharedHWSurface) {
         // this method should fill hwdata and shared_header fields if success
         video->AttachSharedHWSurface (video, surface, fd, map_size, with_wr);
diff --git a/src/newgal/surface.c b/src/newgal/surface.c
index d3da44b2..b9544af8 100644
--- a/src/newgal/surface.c
+++ b/src/newgal/surface.c
@@ -1841,6 +1841,11 @@ void GAL_FreeSurface (GAL_Surface *surface)
         else
             GAL_FreeSharedSurfaceData(surface);
 
+        if (surface->fd >= 0) {
+            close(surface->fd);
+            surface->fd = -1;
+        }
+
         surface->hwdata = NULL;
         surface->pixels = NULL;
     }
diff --git a/src/newgal/video.c b/src/newgal/video.c
index c1653446..65fdc13d 100644
--- a/src/newgal/video.c
+++ b/src/newgal/video.c
@@ -918,9 +918,9 @@ BOOL GAL_SyncUpdate (GAL_Surface *surface)
 
 #ifdef _MGSCHEMA_COMPOSITING
     if (surface->shared_header) {
-        LOCK_SURFACE_SEM (surface->shared_header->sem_num);
+        __mg_lock_file_for_write (surface->fd);
         mark_surface_dirty (surface, numrects, rects);
-        UNLOCK_SURFACE_SEM (surface->shared_header->sem_num);
+        __mg_unlock_file_for_write (surface->fd);
     }
     else if (surface->dirty_info) {
         mark_surface_dirty (surface, numrects, rects);
diff --git a/src/newgdi/shared-surface.c b/src/newgdi/shared-surface.c
index 0db0ca87..b952e79a 100644
--- a/src/newgdi/shared-surface.c
+++ b/src/newgdi/shared-surface.c
@@ -128,8 +128,7 @@ HSURF GUIAPI CreateSharedSurface(GHANDLE video, const char *name, DWORD flags,
 
         int result;
         if (IsServer()) {
-            result = __mg_nssurf_map_operate_srv(&nssurf_req, 0,
-                    nssurf->shared_header->fd);
+            result = __mg_nssurf_map_operate_srv(&nssurf_req, 0, nssurf->fd);
         }
         else {
             REQUEST req;
@@ -138,7 +137,7 @@ HSURF GUIAPI CreateSharedSurface(GHANDLE video, const char *name, DWORD flags,
             req.data = &nssurf_req;
             req.len_data = sizeof(OPERATENSSURFINFO);
 
-            if (ClientRequestEx2(&req, NULL, 0, nssurf->shared_header->fd,
+            if (ClientRequestEx2(&req, NULL, 0, nssurf->fd,
                         &result, sizeof(result), NULL)) {
                 _ERR_PRINTF("BAD_REQUEST: when setting fd of the new shared surface.\n");
                 goto failed;
@@ -307,7 +306,7 @@ const char *GUIAPI GetSharedSurfaceInfo(HSURF surf, int *fd,
     }
 
     if (fd) {
-        *fd = surf->shared_header->fd;
+        *fd = surf->fd;
     }
 
     if (size) {
@@ -341,13 +340,7 @@ BOOL GUIAPI LockSharedSurface(HSURF surf, unsigned *dirty_age,
         goto failed;
     }
 
-    if (surf->flags & GAL_SSURF_LOCKED) {
-        _WRN_PRINTF("INVALID_CALL: surface locked: %p\n", surf);
-        goto failed;
-    }
-
-    LOCK_SURFACE_SEM(surf->shared_header->sem_num);
-    surf->flags |= GAL_SSURF_LOCKED;
+    __mg_lock_file_for_read(surf->fd);
 
     if (dirty_age) {
         *dirty_age = surf->shared_header->dirty_info.dirty_age;
@@ -374,13 +367,7 @@ BOOL GUIAPI UnlockSharedSurface(HSURF surf, BOOL clear_dirty)
         goto failed;
     }
 
-    if (!(surf->flags & GAL_SSURF_LOCKED)) {
-        _WRN_PRINTF("INVALID_CALL: surface not locked: %p\n", surf);
-        goto failed;
-    }
-
-    UNLOCK_SURFACE_SEM(surf->shared_header->sem_num);
-    surf->flags &= ~GAL_SSURF_LOCKED;
+    __mg_unlock_file_for_read(surf->fd);
 
     if (clear_dirty) {
         surf->dirty_info->nr_dirty_rcs = 0;
diff --git a/src/server/layer.c b/src/server/layer.c
index e9ae868e..1add76bc 100644
--- a/src/server/layer.c
+++ b/src/server/layer.c
@@ -910,7 +910,7 @@ const ZNODEHEADER* GUIAPI ServerGetWinZNodeHeader (MG_Layer* layer,
         if (hdr->lock_count == 0) {
             if (pdc->surface->shared_header) {
                 // XXX: consider timeout.
-                LOCK_SURFACE_SEM (pdc->surface->shared_header->sem_num);
+                __mg_lock_file_for_read(pdc->surface->fd);
             }
 
             hdr->dirty_age = pdc->surface->dirty_info->dirty_age;
@@ -962,7 +962,7 @@ const ZNODEHEADER* GUIAPI ServerGetPopupMenuZNodeHeader (int idx,
         if (hdr->lock_count == 0) {
             if (pdc->surface->shared_header) {
                 // XXX: consider timeout
-                LOCK_SURFACE_SEM (pdc->surface->shared_header->sem_num);
+                __mg_lock_file_for_read(pdc->surface->fd);
             }
 
             hdr->dirty_age = pdc->surface->dirty_info->dirty_age;
@@ -1006,7 +1006,7 @@ BOOL GUIAPI ServerReleaseWinZNodeHeader (MG_Layer* layer, int idx_znode)
         hdr->lock_count--;
         if (hdr->lock_count == 0) {
             if (pdc->surface->shared_header)
-                UNLOCK_SURFACE_SEM (pdc->surface->shared_header->sem_num);
+                __mg_unlock_file_for_read(pdc->surface->fd);
 
             hdr->dirty_age = 0;
             hdr->nr_dirty_rcs = 0;
@@ -1035,7 +1035,7 @@ BOOL GUIAPI ServerReleasePopupMenuZNodeHeader (int idx)
         hdr->lock_count--;
         if (hdr->lock_count == 0) {
             if (pdc->surface->shared_header)
-                UNLOCK_SURFACE_SEM (pdc->surface->shared_header->sem_num);
+                __mg_unlock_file_for_read(pdc->surface->fd);
 
             hdr->dirty_age = 0;
             hdr->nr_dirty_rcs = 0;
diff --git a/src/server/request.c b/src/server/request.c
index 2128e684..cd7309b9 100644
--- a/src/server/request.c
+++ b/src/server/request.c
@@ -903,7 +903,7 @@ int __mg_get_shared_surface_srv(const char *itn_name, SHAREDSURFINFO *info)
             __gal_fake_screen->shared_header) {
         info->flags = __gal_fake_screen->flags;
         info->size = __gal_fake_screen->shared_header->map_size;
-        fd = __gal_fake_screen->shared_header->fd;
+        fd = __gal_fake_screen->fd;
     }
     else if (strncmp(itn_name, APPSF_NAME_PREFIX,
                 sizeof(APPSF_NAME_PREFIX) - 1) == 0) {
@@ -940,7 +940,7 @@ int __mg_get_shared_surface_srv(const char *itn_name, SHAREDSURFINFO *info)
         info->height = pdc->surface->shared_header->height;
         info->pitch = pdc->surface->shared_header->pitch;
         info->offset = pdc->surface->shared_header->pixels_off;
-        fd = znode->fd;
+        fd = pdc->surface->fd;
     }
 
 done: