linux-kernel - Re: [PATCH v2 1/2] mm: move mmap/vma locking logic into specific files

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Message-ID: <4782b071-6008-4fd1-b762-65a575dc333a@suse.cz>
Date: Wed, 16 Apr 2025 16:39:50 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>,
 Matthew Wilcox <willy@...radead.org>, "Paul E . McKenney"
 <paulmck@...nel.org>, SeongJae Park <sj@...nel.org>,
 Shakeel Butt <shakeel.butt@...ux.dev>, David Hildenbrand <david@...hat.com>,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 1/2] mm: move mmap/vma locking logic into specific
 files

On 4/16/25 12:38, Lorenzo Stoakes wrote:
> Currently the VMA and mmap locking logic is entangled in two of the most
> overwrought files in mm - include/linux/mm.h and mm/memory.c. Separate this
> logic out so we can more easily make changes and create an appropriate
> MAINTAINERS entry that spans only the logic relating to locking.
> 
> This should have no functional change. Care is taken to avoid dependency
> loops, we must regrettably keep release_fault_lock() and
> assert_fault_locked() in mm.h as a result due to the dependence on the
> vm_fault type.
> 
> Additionally we must declare rcuwait_wake_up() manually to avoid a
> dependency cycle on linux/rcuwait.h.
> 
> Additionally move the nommu implementatino of lock_mm_and_find_vma() to
> mmap_lock.c so everything lock-related is in one place.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

> diff --git a/mm/mmap_lock.c b/mm/mmap_lock.c
> index e7dbaf96aa17..5f725cc67334 100644
> --- a/mm/mmap_lock.c
> +++ b/mm/mmap_lock.c
> @@ -42,3 +42,276 @@ void __mmap_lock_do_trace_released(struct mm_struct *mm, bool write)
>  }
>  EXPORT_SYMBOL(__mmap_lock_do_trace_released);
>  #endif /* CONFIG_TRACING */
> +
> +#ifdef CONFIG_MMU
> +#ifdef CONFIG_PER_VMA_LOCK

CONFIG_MMU is implied by CONFIG_PER_VMA_LOCK so you could move the first
#ifdef later to make only #ifdef CONFIG_LOCK_MM_AND_FIND_VMA nested in it.
But doesn't matter that much.