linux-kernel - Re: [RFC 08/14] fork: separate vmap stack alloction and free calls

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Date: Sun, 17 Mar 2024 11:15:30 -0400
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
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Subject: Re: [RFC 08/14] fork: separate vmap stack alloction and free calls

On Sun, Mar 17, 2024 at 10:52 AM Christophe JAILLET
<christophe.jaillet@...adoo.fr> wrote:
>
> Le 11/03/2024 à 17:46, Pasha Tatashin a écrit :
> > In preparation for the dynamic stacks, separate out the
> > __vmalloc_node_range and vfree calls from the vmap based stack
> > allocations. The dynamic stacks will use their own variants of these
> > functions.
> >
> > Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> > ---
> >   kernel/fork.c | 53 ++++++++++++++++++++++++++++++---------------------
> >   1 file changed, 31 insertions(+), 22 deletions(-)
> >
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index 3004e6ce6c65..bbae5f705773 100644
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -204,6 +204,29 @@ static bool try_release_thread_stack_to_cache(struct vm_struct *vm_area)
> >       return false;
> >   }
> >
> > +static inline struct vm_struct *alloc_vmap_stack(int node)
> > +{
> > +     void *stack;
> > +
> > +     /*
> > +      * Allocated stacks are cached and later reused by new threads,
> > +      * so memcg accounting is performed manually on assigning/releasing
> > +      * stacks to tasks. Drop __GFP_ACCOUNT.
> > +      */
> > +     stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
> > +                                  VMALLOC_START, VMALLOC_END,
> > +                                  THREADINFO_GFP & ~__GFP_ACCOUNT,
> > +                                  PAGE_KERNEL,
> > +                                  0, node, __builtin_return_address(0));
> > +
> > +     return (stack) ? find_vm_area(stack) : NULL;
>
> Nit: superfluous ()

Thank you.

>
> > +}
>
> ...
>