Re: [PATCH] mm/vmalloc: Do not warn on -ENOMEM from va_alloc()

[Baoquan He]

On 08/02/26 at 12:46pm, Uladzislau Rezki (Sony) wrote:
> Since vmalloc() accepts non-blocking GFP flags, allocation
> requests may fail when callers pass restrictive GFP masks.
> 
> va_clip() may return -ENOMEM when its GFP_NOWAIT fallback
> allocation fails during NE_FIT_TYPE splitting. This is an
> expected failure, so va_alloc() should return the error
> without triggering a kernel splat.
> 
> Reported-by: syzbot+61c997e6be1d9bb300ba@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> ---
>  mm/vmalloc.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 1afca3568b9b..7a0cbba3d29d 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1817,8 +1817,10 @@ va_alloc(struct vmap_area *va,
>  
>  	/* Update the free vmap_area. */
>  	ret = va_clip(root, head, va, nva_start_addr, size);
> -	if (WARN_ON_ONCE(ret))
> +	if (ret) {
> +		WARN_ON_ONCE(ret != -ENOMEM);
>  		return ret;
> +	}
>  
>  	return nva_start_addr;
>  }
> @@ -1891,12 +1893,9 @@ preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node)
>  
>  	/*
>  	 * Preload this CPU with one extra vmap_area object. It is used
> -	 * when fit type of free area is NE_FIT_TYPE. It guarantees that
> -	 * a CPU that does an allocation is preloaded.
> -	 *
> -	 * We do it in non-atomic context, thus it allows us to use more
> -	 * permissive allocation masks to be more stable under low memory
> -	 * condition and high memory pressure.
> +	 * when fit type of free area is NE_FIT_TYPE. It is best effort
> +	 * pre-loading. If it fails va_clip() may return -ENOMEM from its
> +	 * GFP_NOWAIT fallback.
>  	 */
>  	if (!this_cpu_read(ne_fit_preload_node))
>  		va = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);

LGTM,

Reviewed-by: Baoquan He <baoquan.he@xxxxxxxxx>