linux-kernel - Re: [PATCH 1/2] maple_tree: fix alloc node fail issue

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Message-ID: <7ei6xebky5shub5qlat5t4g4sznfzlyqrjqsalcbfxhza6ake6@6xnab32uymhk>
Date: Mon, 14 Oct 2024 21:17:06 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Cc: Jiazi Li <jqqlijiazi@...il.com>, linux-kernel@...r.kernel.org,
        maple-tree@...ts.infradead.org
Subject: Re: [PATCH 1/2] maple_tree: fix alloc node fail issue

Andrew,

I think these two were missed.  Can you please pick them up?

Thanks,
Liam

* Liam R. Howlett <Liam.Howlett@...cle.com> [240626 12:06]:
> From: Jiazi Li <jqqlijiazi@...il.com>
> 
> In the following code, the second call to the mas_node_count will
> return -ENOMEM:
> 
> 	mas_node_count(mas, MAPLE_ALLOC_SLOTS + 1);
> 	mas_node_count(mas, MAPLE_ALLOC_SLOTS * 2 + 2);
> 
> This is because there may be some full maple_alloc node in current
> maple state. Use full maple_alloc node will make max_req equal to 0.
> And it leads to mt_alloc_bulk return 0.
> As a result, mas_node_count set mas.node to MA_ERROR(-ENOMEM).
> 
> Find a non-full maple_alloc node, and if necessary, use this non-full
> node in the next while loop.
> 
> Fixes: 54a611b60590 ("Maple Tree: add new data structure")
> Suggested-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> Signed-off-by: Jiazi Li <jqqlijiazi@...il.com>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
>  lib/maple_tree.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 634d49e39a02..fe5c6fab26c3 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -1272,7 +1272,10 @@ static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
>  
>  		node->node_count += count;
>  		allocated += count;
> -		node = node->slot[0];
> +		/* find a non-full node*/
> +		do {
> +			node = node->slot[0];
> +		} while (unlikely(node->node_count == MAPLE_ALLOC_SLOTS));
>  		requested -= count;
>  	}
>  	mas->alloc->total = allocated;
> -- 
> 2.43.0
>