r3357: removed the need to use TDB_CLEAR_IF_FIRST in Samba4.

We found a few months ago that TDB_CLEAR_IF_FIRST is extremely
inefficient for large numbers of connections, due to a fundamental
limitation in the way posix byte range locking is implemented. Rather
than the nasty workaround we had for Samba3, we now have a single
"cleanup tmp files" function that runs when smbd starts. That deletes
the tmp tdbs, so TDB_CLEAR_IF_FIRST is not needed at all.
(This used to be commit ffa285bc78)

source4/lib/util.c

@@ -705,15 +705,18 @@ char *name_to_fqdn(TALLOC_CTX *mem_ctx, const char *name)
 
 char *lock_path(TALLOC_CTX* mem_ctx, const char *name)
 {
-	char *fname;
+	char *fname, *dname;
 
-	fname = talloc_strdup(mem_ctx, lp_lockdir());
-	trim_string(fname,"","/");
+	dname = talloc_strdup(mem_ctx, lp_lockdir());
+	trim_string(dname,"","/");
 	
-	if (!directory_exist(fname,NULL))
-		mkdir(fname,0755);
+	if (!directory_exist(dname,NULL)) {
+		mkdir(dname,0755);
+	}
 	
-	fname = talloc_asprintf(mem_ctx, "%s/%s", fname, name);
+	fname = talloc_asprintf(mem_ctx, "%s/%s", dname, name);
+
+	talloc_free(dname);
 
 	return fname;
 }

source4/libcli/unexpected.c

@@ -50,7 +50,7 @@ void unexpected_packet(struct packet_struct *p)
 		mem_ctx = talloc_init("receive_unexpected");
 		if (!mem_ctx) return;
 		tdbd = tdb_wrap_open(NULL, lock_path(mem_ctx, "unexpected.tdb"), 0, 
-				     TDB_CLEAR_IF_FIRST|TDB_DEFAULT,
+				     TDB_DEFAULT,
 				     O_RDWR | O_CREAT, 0644);
 		talloc_destroy(mem_ctx);
 		if (!tdbd) {

source4/ntvfs/common/brlock.c

@@ -84,7 +84,7 @@ struct brl_context *brl_init(TALLOC_CTX *mem_ctx, servid_t server, uint16_t tid,
 
 	path = lock_path(brl, "brlock.tdb");
 	brl->w = tdb_wrap_open(brl, path, 0,  
-			       TDB_DEFAULT|TDB_CLEAR_IF_FIRST,
+			       TDB_DEFAULT,
 			       O_RDWR|O_CREAT, 0600);
 	talloc_free(path);
 	if (brl->w == NULL) {

source4/ntvfs/common/opendb.c

@@ -88,7 +88,7 @@ struct odb_context *odb_init(TALLOC_CTX *mem_ctx, servid_t server, uint16_t tid,
 
 	path = lock_path(odb, "openfiles.tdb");
 	odb->w = tdb_wrap_open(odb, path, 0,  
-			       TDB_DEFAULT|TDB_CLEAR_IF_FIRST,
+			       TDB_DEFAULT,
 			       O_RDWR|O_CREAT, 0600);
 	talloc_free(path);
 	if (odb->w == NULL) {

source4/smbd/rewrite.c

@@ -19,18 +19,12 @@ BOOL share_access_check(struct smbsrv_request *req, struct smbsrv_tcon *tcon, in
 { return True; }
 
 /*
- * initialize an smb process
+ * initialize an smb process. Guaranteed to be called only once per
+ * smbd instance (so it can assume it is starting from scratch, and
+ * delete temporary files etc)
  */
 void smbd_process_init(void)
 {
-	TALLOC_CTX *mem_ctx;
-
-	mem_ctx = talloc_init("smbd_process_init talloc");
-	if (!mem_ctx) {
-		DEBUG(0,("smbd_process_init: ERROR: No memory\n"));
-		exit(1);
-	}
-
 	/* possibly reload the services file. */
 	reload_services(NULL, True);
 
@@ -39,9 +33,7 @@ void smbd_process_init(void)
 			DEBUG(2,("Changed root to %s\n", lp_rootdir()));
 	}
 
-	/* Start old-style secrets subsystem */
-	
-	talloc_destroy(mem_ctx);
+	service_cleanup_tmp_files();
 }
 
 void init_subsystems(void)

source4/smbd/service.c

@@ -349,3 +349,33 @@ void service_close_listening_sockets(struct server_context *srv_ctx)
 		}
 	}
 }
+
+
+/*
+  cleanup temporary files. This is the new alternative to
+  TDB_CLEAR_IF_FIRST. Unfortunately TDB_CLEAR_IF_FIRST is not
+  efficient on unix systems due to the lack of scaling of the byte
+  range locking system. So instead of putting the burden on tdb to
+  cleanup tmp files, this function deletes them. You need to expand
+  the list here as appropriate.
+*/
+void service_cleanup_tmp_files(void)
+{
+	const char *list[] = { 
+		"openfiles.tdb",
+		"brlock.tdb",
+		"unexpected.tdb"};
+	int i;
+	for (i=0;i<ARRAY_SIZE(list);i++) {
+		char *path = lock_path(NULL, list[i]);
+		int ret;
+		ret = unlink(path);
+		if (ret == -1 && 
+		    errno != ENOENT &&
+		    errno != ENOTDIR) {
+			DEBUG(0,("Failed to cleanup '%s'\n", path));
+			smb_panic("unable to cleanup temporary files\n");
+		}
+		talloc_free(path);
+	}
+}