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

[Vlastimil Babka <vbabka@suse.cz>]

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@oracle.com>
> Reviewed-by: Suren Baghdasaryan <surenb@google.com>

Reviewed-by: Vlastimil Babka <vbabka@suse.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.