fork: clean-up ifdef logic around stack allocation

Patch series "fork: Page operation cleanups in the fork code", v3.

This patchset consists of outtakes from a 1 year+ old patchset from Pasha,
which all stand on their own.  See:
https://lore.kernel.org/all/[email protected]/

These are good cleanups for readability so I split these off, rebased on
v6.15-rc1, addressed review comments and send them separately.

All mentions of dynamic stack are removed from the patchset as we have no
idea whether that will go anywhere.


This patch (of 3):

There is unneeded OR in the ifdef functions that are used to allocate and
free kernel stacks based on direct map or vmap.

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

[[email protected]: rebased]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Pasha Tatashin <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Linus Walleij <[email protected]>
Acked-by: Mike Rapoport (Microsoft) <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: soleen

kernel/fork.c

@@ -185,13 +185,7 @@ 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.
@@ -342,7 +336,13 @@ 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)
 {
@@ -374,8 +374,7 @@ 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;
 
@@ -414,7 +413,8 @@ 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;