Commit 90eb270d authored by Pasha Tatashin's avatar Pasha Tatashin Committed by Andrew Morton
Browse files

fork: clean-up naming of vm_stack/vm_struct variables in vmap stacks code 

There are two data types: "struct vm_struct" and "struct vm_stack" that
have the same local variable names: vm_stack, or vm, or s, which makes the
code confusing to read.

Change the code so the naming is consistent:

struct vm_struct is always called vm_area
struct vm_stack is always called vm_stack

One change altering vfree(vm_stack) to vfree(vm_area->addr) may look like
a semantic change but it is not: vm_area->addr points to the vm_stack. 
This was done to improve readability.

[linus.walleij@linaro.org: rebased and added new users of the variable names, address review comments]
Link: https://lore.kernel.org/20240311164638.2015063-4-pasha.tatashin@soleen.com
Link: https://lkml.kernel.org/r/20250509-fork-fixes-v3-2-e6c69dd356f2@linaro.org


Signed-off-by: default avatarPasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Acked-by: default avatarMike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 85e1f758

kernel/fork.c

+29 −31
Original line number Diff line number Diff line
@@ -198,14 +198,14 @@ struct vm_stack { 
	struct vm_struct *stack_vm_area;

};



static bool try_release_thread_stack_to_cache(struct vm_struct *vm)

static bool try_release_thread_stack_to_cache(struct vm_struct *vm_area)

{

	unsigned int i;



	for (i = 0; i < NR_CACHED_STACKS; i++) {

		struct vm_struct *tmp = NULL;



		if (this_cpu_try_cmpxchg(cached_stacks[i], &tmp, vm))

		if (this_cpu_try_cmpxchg(cached_stacks[i], &tmp, vm_area))

			return true;

	}

	return false;
@@ -214,11 +214,12 @@ static bool try_release_thread_stack_to_cache(struct vm_struct *vm) 
static void thread_stack_free_rcu(struct rcu_head *rh)

{

	struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu);

	struct vm_struct *vm_area = vm_stack->stack_vm_area;



	if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area))

		return;



	vfree(vm_stack);

	vfree(vm_area->addr);

}



static void thread_stack_delayed_free(struct task_struct *tsk)
@@ -231,32 +232,32 @@ static void thread_stack_delayed_free(struct task_struct *tsk) 


static int free_vm_stack_cache(unsigned int cpu)

{

	struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);

	struct vm_struct **cached_vm_stack_areas = per_cpu_ptr(cached_stacks, cpu);

	int i;



	for (i = 0; i < NR_CACHED_STACKS; i++) {

		struct vm_struct *vm_stack = cached_vm_stacks[i];

		struct vm_struct *vm_area = cached_vm_stack_areas[i];



		if (!vm_stack)

		if (!vm_area)

			continue;



		vfree(vm_stack->addr);

		cached_vm_stacks[i] = NULL;

		vfree(vm_area->addr);

		cached_vm_stack_areas[i] = NULL;

	}



	return 0;

}



static int memcg_charge_kernel_stack(struct vm_struct *vm)

static int memcg_charge_kernel_stack(struct vm_struct *vm_area)

{

	int i;

	int ret;

	int nr_charged = 0;



	BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);

	BUG_ON(vm_area->nr_pages != THREAD_SIZE / PAGE_SIZE);



	for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {

		ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);

		ret = memcg_kmem_charge_page(vm_area->pages[i], GFP_KERNEL, 0);

		if (ret)

			goto err;

		nr_charged++;
@@ -264,38 +265,35 @@ static int memcg_charge_kernel_stack(struct vm_struct *vm) 
	return 0;

err:

	for (i = 0; i < nr_charged; i++)

		memcg_kmem_uncharge_page(vm->pages[i], 0);

		memcg_kmem_uncharge_page(vm_area->pages[i], 0);

	return ret;

}



static int alloc_thread_stack_node(struct task_struct *tsk, int node)

{

	struct vm_struct *vm;

	struct vm_struct *vm_area;

	void *stack;

	int i;



	for (i = 0; i < NR_CACHED_STACKS; i++) {

		struct vm_struct *s;



		s = this_cpu_xchg(cached_stacks[i], NULL);



		if (!s)

		vm_area = this_cpu_xchg(cached_stacks[i], NULL);

		if (!vm_area)

			continue;



		/* Reset stack metadata. */

		kasan_unpoison_range(s->addr, THREAD_SIZE);

		kasan_unpoison_range(vm_area->addr, THREAD_SIZE);



		stack = kasan_reset_tag(s->addr);

		stack = kasan_reset_tag(vm_area->addr);



		/* Clear stale pointers from reused stack. */

		memset(stack, 0, THREAD_SIZE);



		if (memcg_charge_kernel_stack(s)) {

			vfree(s->addr);

		if (memcg_charge_kernel_stack(vm_area)) {

			vfree(vm_area->addr);

			return -ENOMEM;

		}



		tsk->stack_vm_area = s;

		tsk->stack_vm_area = vm_area;

		tsk->stack = stack;

		return 0;

	}
@@ -311,8 +309,8 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) 
	if (!stack)

		return -ENOMEM;



	vm = find_vm_area(stack);

	if (memcg_charge_kernel_stack(vm)) {

	vm_area = find_vm_area(stack);

	if (memcg_charge_kernel_stack(vm_area)) {

		vfree(stack);

		return -ENOMEM;

	}
@@ -321,7 +319,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) 
	 * free_thread_stack() can be called in interrupt context,

	 * so cache the vm_struct.

	 */

	tsk->stack_vm_area = vm;

	tsk->stack_vm_area = vm_area;

	stack = kasan_reset_tag(stack);

	tsk->stack = stack;

	return 0;
@@ -517,11 +515,11 @@ void vm_area_free(struct vm_area_struct *vma) 
static void account_kernel_stack(struct task_struct *tsk, int account)

{

	if (IS_ENABLED(CONFIG_VMAP_STACK)) {

		struct vm_struct *vm = task_stack_vm_area(tsk);

		struct vm_struct *vm_area = task_stack_vm_area(tsk);

		int i;



		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)

			mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,

			mod_lruvec_page_state(vm_area->pages[i], NR_KERNEL_STACK_KB,

					      account * (PAGE_SIZE / 1024));

	} else {

		void *stack = task_stack_page(tsk);
@@ -537,12 +535,12 @@ void exit_task_stack_account(struct task_struct *tsk) 
	account_kernel_stack(tsk, -1);



	if (IS_ENABLED(CONFIG_VMAP_STACK)) {

		struct vm_struct *vm;

		struct vm_struct *vm_area;

		int i;



		vm = task_stack_vm_area(tsk);

		vm_area = task_stack_vm_area(tsk);

		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)

			memcg_kmem_uncharge_page(vm->pages[i], 0);

			memcg_kmem_uncharge_page(vm_area->pages[i], 0);

	}

}