linux-kernel - Re: [PATCH v2 2/7] mm/vmalloc.c: add flags to mark vm_map

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Date:   Sat, 17 Dec 2022 11:44:22 +0000
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, urezki@...il.com,
        stephen.s.brennan@...cle.com, willy@...radead.org,
        akpm@...ux-foundation.org, hch@...radead.org
Subject: Re: [PATCH v2 2/7] mm/vmalloc.c: add flags to mark vm_map_ram area

On Sat, Dec 17, 2022 at 09:54:30AM +0800, Baoquan He wrote:
> @@ -2229,8 +2236,12 @@ void vm_unmap_ram(const void *mem, unsigned int count)
>  		return;
>  	}
>
> -	va = find_vmap_area(addr);
> +	spin_lock(&vmap_area_lock);
> +	va = __find_vmap_area((unsigned long)addr, &vmap_area_root);
>  	BUG_ON(!va);
> +	if (va)
> +		va->flags &= ~VMAP_RAM;
> +	spin_unlock(&vmap_area_lock);
>  	debug_check_no_locks_freed((void *)va->va_start,
>  				    (va->va_end - va->va_start));
>  	free_unmap_vmap_area(va);

Would it be better to perform the BUG_ON() after the lock is released? You
already check if va exists before unmasking so it's safe.

Also, do we want to clear VMAP_BLOCK here?