linux-kernel - Re: [PATCH v2 2/4] dax: add stub for pmdp_huge_clear

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Message-ID: <20161223134457.GG22679@quack2.suse.cz>
Date:   Fri, 23 Dec 2016 14:44:57 +0100
From:   Jan Kara <jack@...e.cz>
To:     Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>, Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Dave Hansen <dave.hansen@...el.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        linux-arch@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH v2 2/4] dax: add stub for pmdp_huge_clear_flush()

On Thu 22-12-16 14:18:54, Ross Zwisler wrote:
> Add a pmdp_huge_clear_flush() stub for configs that don't define
> CONFIG_TRANSPARENT_HUGEPAGE.
> 
> We use a WARN_ON_ONCE() instead of a BUILD_BUG() because in the DAX code at
> least we do want this compile successfully even for configs without
> CONFIG_TRANSPARENT_HUGEPAGE.  It'll be a runtime decision whether we call
> this code gets called, based on whether we find DAX PMD entries in our
> tree.  We shouldn't ever find such PMD entries for
> !CONFIG_TRANSPARENT_HUGEPAGE configs, so this function should never be
> called.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  include/asm-generic/pgtable.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index 18af2bc..65e9536 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -178,9 +178,19 @@ extern pte_t ptep_clear_flush(struct vm_area_struct *vma,
>  #endif
>  
>  #ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  extern pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
>  			      unsigned long address,
>  			      pmd_t *pmdp);
> +#else
> +static inline pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
> +			      unsigned long address,
> +			      pmd_t *pmdp)
> +{
> +	WARN_ON_ONCE(1);
> +	return *pmdp;
> +}
> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
>  
>  #ifndef __HAVE_ARCH_PTEP_SET_WRPROTECT
> -- 
> 2.7.4
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR