linux-kernel - Re: [PATCH v2] srcu: Use suitable gfp_flags for the init_srcu_struct

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Message-ID: <5720d304-deaf-439a-be8d-aa6e850f22a2@nvidia.com>
Date: Mon, 22 Dec 2025 19:57:00 -0500
From: Joel Fernandes <joelagnelf@...dia.com>
To: Zqiang <qiang.zhang@...ux.dev>, paulmck@...nel.org, frederic@...nel.org,
 neeraj.upadhyay@...nel.org
Cc: rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] srcu: Use suitable gfp_flags for the
 init_srcu_struct_nodes()

On 12/14/2025 5:14 AM, Zqiang wrote:
> For use the init_srcu_struct*() to initialized srcu structure,
> the srcu structure's->srcu_sup and sda use GFP_KERNEL flags to
> allocate memory. similarly, if set SRCU_SIZING_INIT, the
> srcu_sup's->node can still use GFP_KERNEL flags to allocate
> memory, not need to use GFP_ATOMIC flags all the time.
> 
> Signed-off-by: Zqiang <qiang.zhang@...ux.dev>

Reviewed-by: Joel Fernandes <joelagnelf@...dia.com>

Will apply and send out to the list (soon) with other patches for further review
and testing.

 - Joel

> ---
>  kernel/rcu/srcutree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> index ea3f128de06f..c469c708fdd6 100644
> --- a/kernel/rcu/srcutree.c
> +++ b/kernel/rcu/srcutree.c
> @@ -262,7 +262,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
>  	ssp->srcu_sup->srcu_gp_seq_needed_exp = SRCU_GP_SEQ_INITIAL_VAL;
>  	ssp->srcu_sup->srcu_last_gp_end = ktime_get_mono_fast_ns();
>  	if (READ_ONCE(ssp->srcu_sup->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) {
> -		if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC))
> +		if (!init_srcu_struct_nodes(ssp, is_static ? GFP_ATOMIC : GFP_KERNEL))
>  			goto err_free_sda;
>  		WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_BIG);
>  	}