linux-kernel - Re: [RFC PATCH V3 02/17] mm: Maintain mm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251002142315.000072f2@huawei.com>
Date: Thu, 2 Oct 2025 14:23:15 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Raghavendra K T <raghavendra.kt@....com>
CC: <AneeshKumar.KizhakeVeetil@....com>, <Michael.Day@....com>,
	<akpm@...ux-foundation.org>, <bharata@....com>, <dave.hansen@...el.com>,
	<david@...hat.com>, <dongjoo.linux.dev@...il.com>, <feng.tang@...el.com>,
	<gourry@...rry.net>, <hannes@...xchg.org>, <honggyu.kim@...com>,
	<hughd@...gle.com>, <jhubbard@...dia.com>, <jon.grimm@....com>,
	<k.shutemov@...il.com>, <kbusch@...a.com>, <kmanaouil.dev@...il.com>,
	<leesuyeon0506@...il.com>, <leillc@...gle.com>, <liam.howlett@...cle.com>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<mgorman@...hsingularity.net>, <mingo@...hat.com>, <nadav.amit@...il.com>,
	<nphamcs@...il.com>, <peterz@...radead.org>, <riel@...riel.com>,
	<rientjes@...gle.com>, <rppt@...nel.org>, <santosh.shukla@....com>,
	<shivankg@....com>, <shy828301@...il.com>, <sj@...nel.org>, <vbabka@...e.cz>,
	<weixugc@...gle.com>, <willy@...radead.org>, <ying.huang@...ux.alibaba.com>,
	<ziy@...dia.com>, <dave@...olabs.net>, <yuanchu@...gle.com>,
	<kinseyho@...gle.com>, <hdanton@...a.com>, <harry.yoo@...cle.com>
Subject: Re: [RFC PATCH V3 02/17] mm: Maintain mm_struct list in the system

On Thu, 14 Aug 2025 15:32:52 +0000
Raghavendra K T <raghavendra.kt@....com> wrote:

> The list is used to iterate over all the mm and do PTE A bit scanning.
> mm_slot infrastructure is reused to aid insert and lookup of mm_struct.
> 
> CC: linux-fsdevel@...r.kernel.org

This is part of the tags block.  Some tools moan if you have blank lines
in that.  Alternatively push it below the --- and it won't end up in
the git commit but tooling will still add the +CC.

> 
> Suggested-by: Bharata B Rao <bharata@....com>
> Signed-off-by: Raghavendra K T <raghavendra.kt@....com>

A few minor comments on formatting.

> diff --git a/mm/kscand.c b/mm/kscand.c
> index f7bbbc70c86a..d5b0d3041b0f 100644
> --- a/mm/kscand.c
> +++ b/mm/kscand.c

> +void __kscand_enter(struct mm_struct *mm)
> +{
> +	struct kscand_mm_slot *kscand_slot;
> +	struct mm_slot *slot;
> +	int wakeup;
> +
> +	/* __kscand_exit() must not run from under us */
> +	VM_BUG_ON_MM(kscand_test_exit(mm), mm);
> +
> +	kscand_slot = mm_slot_alloc(kscand_slot_cache);
> +
Similar to below. I'd keep call and error check more closely coupled
visually by dropping this blank line.

> +	if (!kscand_slot)
> +		return;
> +
> +	slot = &kscand_slot->slot;
> +
> +	spin_lock(&kscand_mm_lock);
> +	mm_slot_insert(kscand_slots_hash, mm, slot);
> +
> +	wakeup = list_empty(&kscand_scan.mm_head);

Looks familiar.

wakeup = kscand_has_work()

Or maybe just get rid of that helper and check it explicitly like this.


> +	list_add_tail(&slot->mm_node, &kscand_scan.mm_head);
> +	spin_unlock(&kscand_mm_lock);
> +
> +	mmgrab(mm);
> +	if (wakeup)
> +		wake_up_interruptible(&kscand_wait);
> +}

> +
>  static int start_kscand(void)
>  {
>  	struct task_struct *kthread;
> @@ -149,6 +228,12 @@ static int __init kscand_init(void)
>  {
>  	int err;
>  
> +	kscand_slot_cache = KMEM_CACHE(kscand_mm_slot, 0);
> +

I'd drop this blank line. Keep the call and the error check tightly coupled
in one block of code.

> +	if (!kscand_slot_cache) {
> +		pr_err("kscand: kmem_cache error");
> +		return -ENOMEM;
> +	}
>  	err = start_kscand();
>  	if (err)
>  		goto err_kscand;
> @@ -157,6 +242,7 @@ static int __init kscand_init(void)
>  
>  err_kscand:
>  	stop_kscand();
> +	kscand_destroy();
>  
>  	return err;
>  }