fork: clean up ifdef logic around stack allocation

There is an unneeded OR in the ifdef functions that are used to allocate
and free kernel stacks based on direct map or vmap.  Adding dynamic stack
support would complicate this logic even further.

Therefore, clean up by changing the order so OR is no longer needed.

Link: https://lkml.kernel.org/r/20250618-fork-fixes-v4-1-2e05a2e1f5fc@linaro.org
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/20240311164638.2015063-3-pasha.tatashin@soleen.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/fork.c b/kernel/fork.c
index 6616d173307a92a238fd5b8b74c97b90d551c968..bd8c21d64746163ef22baac6cf7e190fcaca3591 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -188,13 +188,7 @@ static inline void free_task_struct(struct task_struct *tsk)
        kmem_cache_free(task_struct_cachep, tsk);
 }
 
-/*
- * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
- * kmemcache based allocator.
- */
-# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
-
-#  ifdef CONFIG_VMAP_STACK
+#ifdef CONFIG_VMAP_STACK
 /*
  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
  * flush.  Try to minimize the number of calls by caching stacks.
@@ -344,7 +338,13 @@ static void free_thread_stack(struct task_struct *tsk)
        tsk->stack_vm_area = NULL;
 }
 
-#  else /* !CONFIG_VMAP_STACK */
+#else /* !CONFIG_VMAP_STACK */
+
+/*
+ * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
+ * kmemcache based allocator.
+ */
+#if THREAD_SIZE >= PAGE_SIZE
 
 static void thread_stack_free_rcu(struct rcu_head *rh)
 {
@@ -376,8 +376,7 @@ static void free_thread_stack(struct task_struct *tsk)
        tsk->stack = NULL;
 }
 
-#  endif /* CONFIG_VMAP_STACK */
-# else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */
+#else /* !(THREAD_SIZE >= PAGE_SIZE) */
 
 static struct kmem_cache *thread_stack_cache;
 
@@ -416,7 +415,8 @@ void thread_stack_cache_init(void)
        BUG_ON(thread_stack_cache == NULL);
 }
 
-# endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
+#endif /* THREAD_SIZE >= PAGE_SIZE */
+#endif /* CONFIG_VMAP_STACK */
 
 /* SLAB cache for signal_struct structures (tsk->signal) */
 static struct kmem_cache *signal_cachep;