[PATCH] fork: Use THREAD_SIZE_ORDER

[PATCH] fork: Use THREAD_SIZE_ORDER

[Geert Uytterhoeven]

Use the existing THREAD_SIZE_ORDER definition instead of calculating it
from THREAD_SIZE and PAGE_SIZE.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 kernel/fork.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 0d944e92a43ffa13..e79fdfe1f0bf4953 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -252,9 +252,9 @@ static int memcg_charge_kernel_stack(struct vm_struct *vm)
 	int ret;
 	int nr_charged = 0;
 
-	BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
+	BUG_ON(vm->nr_pages != THREAD_SIZE_ORDER);
 
-	for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
+	for (i = 0; i < THREAD_SIZE_ORDER; i++) {
 		ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
 		if (ret)
 			goto err;
@@ -535,7 +535,7 @@ static void account_kernel_stack(struct task_struct *tsk, int account)
 		struct vm_struct *vm = task_stack_vm_area(tsk);
 		int i;
 
-		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
+		for (i = 0; i < THREAD_SIZE_ORDER; i++)
 			mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
 					      account * (PAGE_SIZE / 1024));
 	} else {
@@ -556,7 +556,7 @@ void exit_task_stack_account(struct task_struct *tsk)
 		int i;
 
 		vm = task_stack_vm_area(tsk);
-		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
+		for (i = 0; i < THREAD_SIZE_ORDER; i++)
 			memcg_kmem_uncharge_page(vm->pages[i], 0);
 	}
 }
-- 
2.34.1

Re: [PATCH] fork: Use THREAD_SIZE_ORDER

[Arnd Bergmann]

On Mon, Mar 11, 2024, at 14:44, Geert Uytterhoeven wrote:
> Use the existing THREAD_SIZE_ORDER definition instead of calculating it
> from THREAD_SIZE and PAGE_SIZE.
>
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
>  kernel/fork.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 0d944e92a43ffa13..e79fdfe1f0bf4953 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -252,9 +252,9 @@ static int memcg_charge_kernel_stack(struct vm_struct *vm)
>  	int ret;
>  	int nr_charged = 0;
> 
> -	BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
> +	BUG_ON(vm->nr_pages != THREAD_SIZE_ORDER);
> 

That doesn't look right, THREAD_SIZE_ORDER not the number of
pages but the the log2 of it, right?

I think you want '(1 << THREAD_SIZE_ORDER)', but at that point
it doesn't actually look simpler than the existing code.

    Arnd

Re: [PATCH] fork: Use THREAD_SIZE_ORDER

[Geert Uytterhoeven]

Hi Arnd,

On Mon, Mar 11, 2024 at 2:48 PM Arnd Bergmann <arnd@arndb.de> wrote:
> On Mon, Mar 11, 2024, at 14:44, Geert Uytterhoeven wrote:
> > Use the existing THREAD_SIZE_ORDER definition instead of calculating it
> > from THREAD_SIZE and PAGE_SIZE.
> >
> > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> > ---
> >  kernel/fork.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index 0d944e92a43ffa13..e79fdfe1f0bf4953 100644
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -252,9 +252,9 @@ static int memcg_charge_kernel_stack(struct vm_struct *vm)
> >       int ret;
> >       int nr_charged = 0;
> >
> > -     BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
> > +     BUG_ON(vm->nr_pages != THREAD_SIZE_ORDER);
> >
>
> That doesn't look right, THREAD_SIZE_ORDER not the number of
> pages but the the log2 of it, right?
>
> I think you want '(1 << THREAD_SIZE_ORDER)', but at that point
> it doesn't actually look simpler than the existing code.

Thank you for pointing out my silly mistake.

/me hides in a brown paper bag, with a coffee machine.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds