linux-kernel - Re: [PATCH 2/3] alloc_tag: prevent enabling memory profiling if it was shut down

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Message-ID: <8c4967ca-a125-458f-9998-6de4f8257dd5@gmail.com>
Date: Wed, 10 Sep 2025 16:51:57 -0400
From: Usama Arif <usamaarif642@...il.com>
To: Suren Baghdasaryan <surenb@...gle.com>, akpm@...ux-foundation.org
Cc: kent.overstreet@...ux.dev, vbabka@...e.cz, mhocko@...e.com,
 jackmanb@...gle.com, hannes@...xchg.org, ziy@...dia.com,
 shakeel.butt@...ux.dev, 00107082@....com, pasha.tatashin@...een.com,
 souravpanda@...gle.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] alloc_tag: prevent enabling memory profiling if it
 was shut down



On 10/09/2025 00:34, Suren Baghdasaryan wrote:
> Memory profiling can be shut down due to reasons like a failure during
> initialization. When this happens, the user should not be able to
> re-enable it. Current sysctrl interface does not handle this properly
> and will allow re-enabling memory profiling. Fix this by checking for
> this condition during sysctrl write operation.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
> ---
>  lib/alloc_tag.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 

Acked-by: Usama Arif <usamaarif642@...il.com>



> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index 95688c4cba7a..79891528e7b6 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -767,6 +767,16 @@ struct page_ext_operations page_alloc_tagging_ops = {
>  EXPORT_SYMBOL(page_alloc_tagging_ops);
>  
>  #ifdef CONFIG_SYSCTL

nit: might be good to add a comment here that we are not using default as we dont want to enable
it back if it fails once. But not worth a respin as someone can always check git log if curious.

> +static int proc_mem_profiling_handler(const struct ctl_table *table, int write,
> +				      void *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	if (!mem_profiling_support && write)
> +		return -EINVAL;
> +
> +	return proc_do_static_key(table, write, buffer, lenp, ppos);
> +}
> +
> +
>  static struct ctl_table memory_allocation_profiling_sysctls[] = {
>  	{
>  		.procname	= "mem_profiling",
> @@ -776,7 +786,7 @@ static struct ctl_table memory_allocation_profiling_sysctls[] = {
>  #else
>  		.mode		= 0644,
>  #endif
> -		.proc_handler	= proc_do_static_key,
> +		.proc_handler	= proc_mem_profiling_handler,
>  	},
>  };
>