linux-kernel - Re: [PATCH 2/6] lib/rhashtable: guarantee initial hashtable allocation

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Message-ID: <20180528100237.needq2u5e3v2n642@gondor.apana.org.au>
Date:   Mon, 28 May 2018 18:02:37 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
        tgraf@...g.ch, manfred@...orfullife.com,
        guillaume.knispel@...ersonicimagine.com, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 2/6] lib/rhashtable: guarantee initial hashtable
 allocation

On Thu, May 24, 2018 at 02:11:31PM -0700, Davidlohr Bueso wrote:
>
> +	/*
> +	 * This is api initialization and thus we need to guarantee the
> +	 * initial rhashtable allocation. Upon failure, retry with a
> +	 * smallest possible size, otherwise we exhaust our options with
> +	 * __GFP_NOFAIL.
> +	 */
>  	tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
> -	if (tbl == NULL)
> -		return -ENOMEM;
> +	if (unlikely(tbl == NULL)) {
> +		size = HASH_MIN_SIZE;

You should also take min_size into account.  Yes I know the current
code ignores it unless you also set nelem_hint.  But that's just a
bug.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt