Merge branch 'for-linus-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml

[linux.git] / mm / init-mm.c

diff --git a/mm/init-mm.c b/mm/init-mm.c
index f0179c9c04c26084ba3e76c9954eeb25a2319d1d..a787a319211ef9aea4d0bebb84055b377b52dfae 100644 (file)
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -15,6 +15,16 @@
 #define INIT_MM_CONTEXT(name)
 #endif
 
+/*
+ * For dynamically allocated mm_structs, there is a dynamically sized cpumask
+ * at the end of the structure, the size of which depends on the maximum CPU
+ * number the system can see. That way we allocate only as much memory for
+ * mm_cpumask() as needed for the hundreds, or thousands of processes that
+ * a system typically runs.
+ *
+ * Since there is only one init_mm in the entire system, keep it simple
+ * and size this cpu_bitmask to NR_CPUS.
+ */
 struct mm_struct init_mm = {
        .mm_rb          = RB_ROOT,
        .pgd            = swapper_pg_dir,
@@ -25,5 +35,6 @@ struct mm_struct init_mm = {
        .arg_lock       =  __SPIN_LOCK_UNLOCKED(init_mm.arg_lock),
        .mmlist         = LIST_HEAD_INIT(init_mm.mmlist),
        .user_ns        = &init_user_ns,
+       .cpu_bitmap     = { [BITS_TO_LONGS(NR_CPUS)] = 0},
        INIT_MM_CONTEXT(init_mm)
 };