kernel/cred.c: make init_groups static

init_groups is declared in both cred.h and init_task.h, but it is not
actually referenced anywhere outside of cred.c where it is defined.  So
make it static and remove the declarations.

Link: https://lkml.kernel.org/r/20210310220102.2484201-1-linux@rasmusvillemoes.dkSigned-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/cred.h

@@ -53,7 +53,6 @@ do {							\
 		groups_free(group_info);		\
 } while (0)
 
-extern struct group_info init_groups;
 #ifdef CONFIG_MULTIUSER
 extern struct group_info *groups_alloc(int);
 extern void groups_free(struct group_info *);

include/linux/init_task.h

@@ -25,7 +25,6 @@
 extern struct files_struct init_files;
 extern struct fs_struct init_fs;
 extern struct nsproxy init_nsproxy;
-extern struct group_info init_groups;
 extern struct cred init_cred;
 
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE

kernel/cred.c

@@ -33,7 +33,7 @@ do {									\
 static struct kmem_cache *cred_jar;
 
 /* init to 2 - one for init_task, one to ensure it is never freed */
-struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
+static struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
 
 /*
  * The initial credentials for the initial task