Subject: Re: [RFC PATCH 3/3] mm/vmalloc.c: change _vm_unmap_aliases() to do purge firstly

From: Thomas Gleixner <[email-masked]>
Date: Mon, 22 May 2023 14:02:34 +0200

On Mon, May 22 2023 at 19:21, Baoquan He wrote:
> On 05/22/23 at 01:10am, Thomas Gleixner wrote:
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 5ca55b357148..4b11a32df49d 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1728,6 +1728,7 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
>  	unsigned int num_purged_areas = 0;
>  	struct list_head local_purge_list;
>  	struct vmap_area *va, *n_va;
> +	struct vmap_block vb;
>  
>  	lockdep_assert_held(&vmap_purge_lock);
>  
> @@ -1736,6 +1737,14 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
>  	list_replace_init(&purge_vmap_area_list, &local_purge_list);
>  	spin_unlock(&purge_vmap_area_lock);
>  
> +	vb = container_of(va, struct vmap_block, va);

This cannot work vmap_area is not embedded in vmap_block. vmap_block::va
is a pointer. vmap_area does not link back to vmap_block, so there is no
way to find it based on a vmap_area.

Aside of that va is not initialized here :)

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