linux-kernel - Re: [PATCH v9 11/17] mm: replace vm_lock and detached flag with a reference count

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Message-ID: <20250113023756.kgu7hdeow7ltsj7m@master>
Date: Mon, 13 Jan 2025 02:37:56 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: akpm@...ux-foundation.org, peterz@...radead.org, willy@...radead.org,
	liam.howlett@...cle.com, lorenzo.stoakes@...cle.com,
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Subject: Re: [PATCH v9 11/17] mm: replace vm_lock and detached flag with a
 reference count

On Fri, Jan 10, 2025 at 08:25:58PM -0800, Suren Baghdasaryan wrote:
> static inline void vma_end_read(struct vm_area_struct *vma) {}
>@@ -908,12 +948,8 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
> 	vma->vm_mm = mm;
> 	vma->vm_ops = &vma_dummy_vm_ops;
> 	INIT_LIST_HEAD(&vma->anon_vma_chain);
>-#ifdef CONFIG_PER_VMA_LOCK
>-	/* vma is not locked, can't use vma_mark_detached() */
>-	vma->detached = true;
>-#endif
> 	vma_numab_state_init(vma);
>-	vma_lock_init(vma);
>+	vma_lock_init(vma, false);

vma_init(vma, mm)
  memset(vma, 0, sizeof(*vma))
  ...
  vma_lock_init(vma, false);

It looks the vm_refcnt must be reset.

BTW, I don't figure out why we want to skip the reset of vm_refcnt. Is this
related to SLAB_TYPESAFE_BY_RCU?

> }
> 

-- 
Wei Yang
Help you, Help me