linux-kernel - Re: [PATCH 2/3] x86/mm: add TLB purge to free pmd/pte page interfaces

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Message-ID: <20180515140549.GE18595@8bytes.org>
Date:   Tue, 15 May 2018 16:05:49 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Toshi Kani <toshi.kani@....com>
Cc:     mhocko@...e.com, akpm@...ux-foundation.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, cpandya@...eaurora.org,
        linux-mm@...ck.org, x86@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 2/3] x86/mm: add TLB purge to free pmd/pte page interfaces

On Mon, Apr 30, 2018 at 11:59:24AM -0600, Toshi Kani wrote:
>  int pud_free_pmd_page(pud_t *pud, unsigned long addr)
>  {
> -	pmd_t *pmd;
> +	pmd_t *pmd, *pmd_sv;
> +	pte_t *pte;
>  	int i;
>  
>  	if (pud_none(*pud))
>  		return 1;
>  
>  	pmd = (pmd_t *)pud_page_vaddr(*pud);
> +	pmd_sv = (pmd_t *)__get_free_page(GFP_KERNEL);

So you need to allocate a page to free a page? It is better to put the
pages into a list with a list_head on the stack.

I am still on favour of just reverting the broken commit and do a
correct and working fix for the/a merge window.


	Joerg