linux-kernel - Re: [RFC PATCH 1/5] sched, fork: Wire BLOG contexts into task lifecycle

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Message-ID: <20251024134409.72275dd4@gandalf.local.home>
Date: Fri, 24 Oct 2025 13:44:09 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Alex Markuze <amarkuze@...hat.com>
Cc: ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, Liam.Howlett@...cle.com, akpm@...ux-foundation.org,
 bsegall@...gle.com, david@...hat.com, dietmar.eggemann@....com,
 idryomov@...il.com, mingo@...hat.com, juri.lelli@...hat.com,
 kees@...nel.org, lorenzo.stoakes@...cle.com, mgorman@...e.de,
 mhocko@...e.com, rppt@...nel.org, peterz@...radead.org, surenb@...gle.com,
 vschneid@...hat.com, vincent.guittot@...aro.org, vbabka@...e.cz,
 xiubli@...hat.com, Slava.Dubeyko@....com
Subject: Re: [RFC PATCH 1/5] sched, fork: Wire BLOG contexts into task
 lifecycle



On Fri, 24 Oct 2025 08:42:55 +0000
Alex Markuze <amarkuze@...hat.com> wrote:

> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 07576479c0ed..e381f8421a11 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1278,6 +1278,13 @@ struct task_struct {
>  	/* Journalling filesystem info: */
>  	void				*journal_info;
>  
> +/* BLOG support - max modules defined here for use by other headers */
> +#define BLOG_MAX_MODULES 8
> +
> +#ifdef CONFIG_BLOG
> +	struct blog_tls_ctx		*blog_contexts[BLOG_MAX_MODULES];
> +#endif
> +
>  	/* Stacked block device info: */
>  	struct bio_list			*bio_list;
>  
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 3da0f08615a9..b06843af05a9 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -24,6 +24,9 @@
>  #include <linux/sched/cputime.h>
>  #include <linux/sched/ext.h>
>  #include <linux/seq_file.h>
> +#ifdef CONFIG_BLOG
> +#include <linux/blog/blog.h>
> +#endif

The proper way to do this is to have the #ifdef in the header file and not
in the C file.

>  #include <linux/rtmutex.h>
>  #include <linux/init.h>
>  #include <linux/unistd.h>
> @@ -186,6 +189,29 @@ static inline struct task_struct *alloc_task_struct_node(int node)
>  
>  static inline void free_task_struct(struct task_struct *tsk)
>  {
> +#ifdef CONFIG_BLOG
> +	/* Clean up any BLOG contexts */
> +	{

There should be a function that gets called here that frees up the context.
This does not belong in the fork.c file.

	blog_free(task);

In the header file have:

#ifdef CONFIG_BLOG
[..]
void blog_free(struct task_struct *task);
#else
static inline blog_free(struct task_struct *task)
{
}
#endif /* CONFIG_BLOG */



> +		struct blog_tls_ctx *contexts[BLOG_MAX_MODULES];
> +		int i;
> +
> +		/* Step 1: Atomically detach all contexts while holding lock */
> +		task_lock(tsk);
> +		for (i = 0; i < BLOG_MAX_MODULES; i++) {
> +			contexts[i] = tsk->blog_contexts[i];
> +			tsk->blog_contexts[i] = NULL;
> +		}
> +		task_unlock(tsk);
> +
> +		/* Step 2: Release contexts outside the lock */
> +		for (i = 0; i < BLOG_MAX_MODULES; i++) {
> +			struct blog_tls_ctx *ctx = contexts[i];
> +
> +			if (ctx && ctx->release)
> +				ctx->release(ctx);
> +		}
> +	}
> +#endif
>  	kmem_cache_free(task_struct_cachep, tsk);
>  }
>  
> @@ -2012,6 +2038,17 @@ __latent_entropy struct task_struct *copy_process(
>  	p = dup_task_struct(current, node);
>  	if (!p)
>  		goto fork_out;
> +
> +#ifdef CONFIG_BLOG
> +	/* Initialize BLOG contexts */
> +	{
> +		int i;
> +
> +		for (i = 0; i < BLOG_MAX_MODULES; i++)
> +			p->blog_contexts[i] = NULL;
> +	}
> +#endif

Same here.

> +
>  	p->flags &= ~PF_KTHREAD;
>  	if (args->kthread)
>  		p->flags |= PF_KTHREAD;

-- Steve