diff --git a/include/file.h b/include/file.h
index b3b89593..c0eee6c1 100644
--- a/include/file.h
+++ b/include/file.h
@@ -77,6 +77,11 @@ struct empfile {
      * visible to caller of ef_write() and are written to the file.
      */
     void (*prewrite)(int id, void *old, void *elt);
+    /*
+     * Called after table size changed, with file type as argument.
+     * Return -1 and set errno to make the operation fail.
+     */
+    int (*onresize)(int type);
 };
 
 struct emptypedstr {
diff --git a/src/lib/common/file.c b/src/lib/common/file.c
index 692ed187..4c63be71 100644
--- a/src/lib/common/file.c
+++ b/src/lib/common/file.c
@@ -156,6 +156,8 @@ ef_open(int type, int how, int nelt)
 	}
     }
 
+    if (ep->onresize && ep->onresize(type) < 0)
+	return 0;
     return 1;
 }
 
@@ -250,6 +252,8 @@ ef_close(int type)
 	ep->fd = -1;
     }
     ep->baseid = ep->cids = ep->fids = 0;
+    if (ep->onresize && ep->onresize(type) < 0)
+	retval = 0;
     return retval;
 }
 
@@ -487,25 +491,27 @@ ef_write(int type, int id, void *from)
     ep = &empfile[type];
     if (CANT_HAPPEN((ep->flags & (EFF_MEM | EFF_PRIVATE)) == EFF_PRIVATE))
 	return 0;
+    if (CANT_HAPPEN((ep->flags & EFF_MEM) ? id >= ep->fids : id > ep->fids))
+	return 0;		/* not implemented */
+    new_seqno(ep, from);
+    if (id >= ep->fids) {
+	/* write beyond end of file extends it, take note */
+	ep->fids = id + 1;
+	if (ep->onresize && ep->onresize(type) < 0)
+	    return 0;
+    }
     if (id >= ep->baseid && id < ep->baseid + ep->cids)
 	cachep = ep->cache + (id - ep->baseid) * ep->size;
     else
 	cachep = NULL;
     if (ep->prewrite)
 	ep->prewrite(id, cachep, from);
-    if (CANT_HAPPEN((ep->flags & EFF_MEM) ? id >= ep->fids : id > ep->fids))
-	return 0;		/* not implemented */
-    new_seqno(ep, from);
     if (ep->fd >= 0) {
 	if (do_write(ep, from, id, 1) < 0)
 	    return 0;
     }
     if (cachep && cachep != from)	/* update the cache if necessary */
 	memcpy(cachep, from, ep->size);
-    if (id >= ep->fids) {
-	/* write beyond end of file extends it, take note */
-	ep->fids = id + 1;
-    }
     return 1;
 }
 
@@ -634,6 +640,8 @@ ef_extend(int type, int count)
 	}
     }
     ep->fids = id + count;
+    if (ep->onresize && ep->onresize(type) < 0)
+	return 0;
     return 1;
 }
 
@@ -723,6 +731,8 @@ ef_truncate(int type, int count)
 	    ep->cids = count - ep->baseid;
     }
 
+    if (ep->onresize && ep->onresize(type) < 0)
+	return 0;
     return 1;
 }
 
diff --git a/src/lib/common/filetable.c b/src/lib/common/filetable.c
index 4894369c..2b92ab5c 100644
--- a/src/lib/common/filetable.c
+++ b/src/lib/common/filetable.c
@@ -62,21 +62,21 @@
 /* Initializers for members flags... */
 /* Unmapped cache */
 #define UNMAPPED_CACHE(type, flags) \
-    sizeof(type), (flags), NULL, 0, 0, 0, 0, -1, NULL, NULL, NULL
+    sizeof(type), (flags), NULL, 0, 0, 0, 0, -1, NULL, NULL, NULL, NULL
 /*
  * Mapped cache, array with known size.
  * Members cids, fids are not set.
  */
 #define ARRAY_CACHE(array, flags) \
     sizeof(*(array)), (flags), (char *)(array), \
-    SZ((array)), 0, 0, 0, -1, NULL, NULL, NULL
+    SZ((array)), 0, 0, 0, -1, NULL, NULL, NULL, NULL
 /*
  * Mapped cache, array with unknown size.
  * Members csize, cids, fids are not set.
  */
 #define PTR_CACHE(ptr, flags) \
     sizeof(*(ptr)), (flags), (char *)(ptr), \
-    0, 0, 0, 0, -1, NULL, NULL, NULL
+    0, 0, 0, 0, -1, NULL, NULL, NULL, NULL
 /*
  * Array-backed table.
  * The array's last element is the sentinel.
@@ -84,7 +84,7 @@
 #define ARRAY_TABLE(array, flags)				\
     sizeof(*(array)), (flags), (char *)(array),			\
     SZ((array)), 0, SZ((array)) - 1, SZ((array)) - 1, -1,	\
-    NULL, NULL, NULL
+    NULL, NULL, NULL, NULL
 
 /* Common configuration table flags */
 #define EFF_CFG (EFF_PRIVATE | EFF_MEM | EFF_STATIC | EFF_SENTINEL)
@@ -145,9 +145,9 @@ struct empfile empfile[] = {
     {EF_LOAN, "loan", "loan", loan_ca,
      UNMAPPED_CACHE(struct lonstr, EFF_TYPED)},
     {EF_MAP, "map", "map", NULL,
-     0, 0, NULL, 0, 0, 0, 0, -1, NULL, NULL, NULL},
+     0, 0, NULL, 0, 0, 0, 0, -1, NULL, NULL, NULL, NULL},
     {EF_BMAP, "bmap", "bmap", NULL,
-     0, 0, NULL, 0, 0, 0, 0, -1, NULL, NULL, NULL},
+     0, 0, NULL, 0, 0, 0, 0, -1, NULL, NULL, NULL, NULL},
     {EF_COMM, "commodity", "commodity", commodity_ca,
      UNMAPPED_CACHE(struct comstr, EFF_TYPED | EFF_OWNER)},
     {EF_LOST, "lost", "lostitems", lost_ca,
@@ -197,7 +197,7 @@ struct empfile empfile[] = {
      ARRAY_TABLE(empfile, EFF_CFG)},
     {EF_VERSION, "version", NULL, NULL,
      sizeof(PACKAGE_STRING), EFF_STATIC, version, 1, 0, 1, 1, -1,
-     NULL, NULL, NULL},
+     NULL, NULL, NULL, NULL},
     {EF_META, "meta", NULL, mdchr_ca,
      PTR_CACHE(mdchr_ca, EFF_CFG)},
 
@@ -237,7 +237,7 @@ struct empfile empfile[] = {
 
     /* Sentinel */
     {EF_BAD, NULL, NULL, NULL,
-     0, 0, NULL, 0, 0, 0, 0, -1, NULL, NULL, NULL},
+     0, 0, NULL, 0, 0, 0, 0, -1, NULL, NULL, NULL, NULL},
 };
 
 static void