mm/mmap: use SZ_{8K, 128K} helper macro

Use SZ_{8K, 128K} helper macro instead of the number in init_user_reserve
and reserve_mem_notifier. This is more readable.

Link: https://lkml.kernel.org/r/20240131031913.2058597-1-yajun.deng@linux.devSigned-off-by: Yajun Deng <yajun.deng@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mmap.c

@@ -3845,7 +3845,7 @@ static int init_user_reserve(void)
 
 	free_kbytes = K(global_zone_page_state(NR_FREE_PAGES));
 
-	sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
+	sysctl_user_reserve_kbytes = min(free_kbytes / 32, SZ_128K);
 	return 0;
 }
 subsys_initcall(init_user_reserve);
@@ -3866,7 +3866,7 @@ static int init_admin_reserve(void)
 
 	free_kbytes = K(global_zone_page_state(NR_FREE_PAGES));
 
-	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
+	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, SZ_8K);
 	return 0;
 }
 subsys_initcall(init_admin_reserve);
@@ -3898,12 +3898,12 @@ static int reserve_mem_notifier(struct notifier_block *nb,
 	case MEM_ONLINE:
 		/* Default max is 128MB. Leave alone if modified by operator. */
 		tmp = sysctl_user_reserve_kbytes;
-		if (0 < tmp && tmp < (1UL << 17))
+		if (tmp > 0 && tmp < SZ_128K)
 			init_user_reserve();
 
 		/* Default max is 8MB.  Leave alone if modified by operator. */
 		tmp = sysctl_admin_reserve_kbytes;
-		if (0 < tmp && tmp < (1UL << 13))
+		if (tmp > 0 && tmp < SZ_8K)
 			init_admin_reserve();
 
 		break;