Re: [RFC 2/7] mm/vmalloc: Support non-blocking GFP flags in alloc_vmap_area()

[Michal Hocko <mhocko@suse.com>]

On Fri 04-07-25 17:25:32, Uladzislau Rezki wrote:
[...]
> @@ -2030,7 +2033,8 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  	 */
>  	va = node_alloc(size, align, vstart, vend, &addr, &vn_id);
>  	if (!va) {
> -		gfp_mask = gfp_mask & GFP_RECLAIM_MASK;
> +		if (allow_block)
> +			gfp_mask = gfp_mask & GFP_RECLAIM_MASK;

I don't follow here and is this even correct?

>  
>  		va = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);
>  		if (unlikely(!va))
> @@ -2057,8 +2061,14 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  	 * If an allocation fails, the error value is
>  	 * returned. Therefore trigger the overflow path.
>  	 */
> -	if (IS_ERR_VALUE(addr))
> +	if (IS_ERR_VALUE(addr)) {
> +		if (!allow_block) {
> +			kmem_cache_free(vmap_area_cachep, va);
> +			return ERR_PTR(-ENOMEM);

I would suggest to add a comment for this. Something like

for blockable requests trigger the overflow paths because that
relies on vmap_purge_lock mutex and blocking notifiers.

> +		}
> +
>  		goto overflow;
> +	}
>  
>  	va->va_start = addr;
>  	va->va_end = addr + size;
> -- 
> 2.39.5

-- 
Michal Hocko
SUSE Labs