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SubjectRe: [RFC 04/14] fork: Remove assumption that vm_area->nr_pages equals to THREAD_SIZE
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Le 11/03/2024 à 17:46, Pasha Tatashin a écrit :
> In many places number of pages in the stack is detremined via
> (THREAD_SIZE / PAGE_SIZE). There is also a BUG_ON() that ensures that
> (THREAD_SIZE / PAGE_SIZE) is indeed equals to vm_area->nr_pages.
>
> However, with dynamic stacks, the number of pages in vm_area will grow
> with stack, therefore, use vm_area->nr_pages to determine the actual
> number of pages allocated in stack.
>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> ---
> kernel/fork.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 60e812825a7a..a35f4008afa0 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -243,13 +243,11 @@ static int free_vm_stack_cache(unsigned int cpu)
>
> static int memcg_charge_kernel_stack(struct vm_struct *vm)

Maybe s/vm/vm_area/ as done in 03/14?

CJ

> {
> - int i;
> - int ret;
> + int i, ret, nr_pages;
> int nr_charged = 0;
>
> - BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
> -
> - for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
> + nr_pages = vm->nr_pages;
> + for (i = 0; i < nr_pages; i++) {
> ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
> if (ret)
> goto err;
> @@ -531,9 +529,10 @@ 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);
> - int i;
> + int i, nr_pages;
>
> - for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
> + nr_pages = vm->nr_pages;
> + for (i = 0; i < nr_pages; i++)
> mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
> account * (PAGE_SIZE / 1024));
> } else {
> @@ -551,10 +550,11 @@ void exit_task_stack_account(struct task_struct *tsk)
>
> if (IS_ENABLED(CONFIG_VMAP_STACK)) {
> struct vm_struct *vm;
> - int i;
> + int i, nr_pages;
>
> vm = task_stack_vm_area(tsk);
> - for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
> + nr_pages = vm->nr_pages;
> + for (i = 0; i < nr_pages; i++)
> memcg_kmem_uncharge_page(vm->pages[i], 0);
> }
> }


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