linux-kernel - Re: [PATCH v5 4/4] hugetlb: allow to free gigantic pages regardless of the configuration

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Date:   Wed, 6 Mar 2019 11:16:44 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Alexandre Ghiti <alex@...ti.fr>, Vlastimil Babka <vbabka@...e.cz>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S . Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v5 4/4] hugetlb: allow to free gigantic pages regardless
 of the configuration

On 3/6/19 11:00 AM, Alexandre Ghiti wrote:
> +static int set_max_huge_pages(struct hstate *h, unsigned long count,
> +			      nodemask_t *nodes_allowed)
>  {
>  	unsigned long min_count, ret;
>  
> -	if (hstate_is_gigantic(h) && !gigantic_page_supported())
> -		return h->max_huge_pages;
> +	/*
> +	 * Gigantic pages allocation depends on the capability for large page
> +	 * range allocation. If the system cannot provide alloc_contig_range,
> +	 * allow users to free gigantic pages.
> +	 */
> +	if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {
> +		spin_lock(&hugetlb_lock);
> +		if (count > persistent_huge_pages(h)) {
> +			spin_unlock(&hugetlb_lock);
> +			return -EINVAL;
> +		}
> +		goto decrease_pool;
> +	}

We talked about it during the last round and I don't seen any mention of
it here in comments or the changelog: Why is this a goto?  Why don't we
just let the code fall through to the "decrease_pool" label?  Why is
this new block needed at all?  Can't we just remove the old check and
let it be?