Why have a separate CONFIG_INIT_SWAPON when we already have CONFIG_SWAPONOFF?

init/Config.in

@@ -35,14 +35,6 @@ config CONFIG_FEATURE_INIT_COREDUMPS
 	  core file sizes.  If this option is disabled, processes
 	  will not generate any core files.
 
-config CONFIG_FEATURE_INIT_SWAPON
-	bool "  Should init run swapon if short on memory?"
-	default y
-	depends on CONFIG_INIT
-	help
-	  If the system has less than one megabyte of total memory, init
-	  will run '/sbin/swapon -a' to add swap memory.
-
 config CONFIG_FEATURE_INIT_SCTTY
 	bool "  Support running commands with a controlling-tty?"
 	default n

init/init.c

@@ -308,37 +308,6 @@ static void set_term(int fd)
 	tcsetattr(fd, TCSANOW, &tty);
 }
 
-#ifdef CONFIG_FEATURE_INIT_SWAPON
-/* How much memory does this machine have?
-   Units are kBytes to avoid overflow on 4GB machines */
-static unsigned int check_free_memory(void)
-{
-	struct sysinfo info;
-	unsigned int result, u, s = 10;
-
-	if (sysinfo(&info) != 0) {
-		bb_perror_msg("Error checking free memory");
-		return -1;
-	}
-
-	/* Kernels 2.0.x and 2.2.x return info.mem_unit==0 with values in bytes.
-	 * Kernels 2.4.0 return info.mem_unit in bytes. */
-	u = info.mem_unit;
-	if (u == 0)
-		u = 1;
-	while ((u & 1) == 0 && s > 0) {
-		u >>= 1;
-		s--;
-	}
-	result = (info.totalram >> s) + (info.totalswap >> s);
-	if (((unsigned long long)result * (unsigned long long)u) > UINT_MAX) {
-		return(UINT_MAX);
-	} else {
-		return(result * u);
-	}
-}
-#endif /* CONFIG_FEATURE_INIT_SWAPON */
-
 static void console_init(void)
 {
 	int fd;
@@ -918,38 +887,6 @@ static void delete_init_action(struct init_action *action)
 	}
 }
 
-#ifdef CONFIG_FEATURE_INIT_SWAPON
-/* Make sure there is enough memory to do something useful. *
- * Calls "swapon -a" if needed so be sure /etc/fstab is present... */
-static void check_memory(void)
-{
-	struct stat statBuf;
-
-	if (check_free_memory() > 1000)
-		return;
-
-#if !defined(__UCLIBC__) || defined(__ARCH_HAS_MMU__)
-	if (stat("/etc/fstab", &statBuf) == 0) {
-		/* swapon -a requires /proc typically */
-		new_init_action(SYSINIT, "/bin/mount -t proc proc /proc", "");
-		/* Try to turn on swap */
-		new_init_action(SYSINIT, "/sbin/swapon -a", "");
-		run_actions(SYSINIT);   /* wait and removing */
-		if (check_free_memory() < 1000)
-			goto goodnight;
-	} else
-		goto goodnight;
-	return;
-#endif
-
-  goodnight:
-	message(CONSOLE, "Sorry, your computer does not have enough memory.");
-	loop_forever();
-}
-#else
-# define check_memory()
-#endif /* CONFIG_FEATURE_INIT_SWAPON */
-
 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
  * then parse_inittab() simply adds in some default
  * actions(i.e., runs INIT_SCRIPT and then starts a pair
@@ -1149,7 +1086,20 @@ extern int init_main(int argc, char **argv)
 	message(MAYBE_CONSOLE | LOG, "init started:  %s", bb_msg_full_version);
 
 	/* Make sure there is enough memory to do something useful. */
-	check_memory();
+	if (ENABLE_SWAPONOFF) {
+		struct sysinfo info;
+
+		if (!sysinfo(&info) &&
+			(info.mem_unit ? : 1) * (long long)info.totalram < MEGABYTE)
+		{
+			message(CONSOLE,"Low memory: forcing swapon.");
+			/* swapon -a requires /proc typically */
+			new_init_action(SYSINIT, "/bin/mount -t proc proc /proc", "");
+			/* Try to turn on swap */
+			new_init_action(SYSINIT, "/sbin/swapon -a", "");
+			run_actions(SYSINIT);   /* wait and removing */
+		}
+	}
 
 	/* Check if we are supposed to be in single user mode */
 	if (argc > 1 && (!strcmp(argv[1], "single") ||