linux-kernel - Re: [PATCH] highmem: Round down the address passed to kunmap_flush_on

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Date:   Fri, 27 Jan 2023 14:53:43 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Ira Weiny <ira.weiny@...el.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
CC:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH] highmem: Round down the address passed to
 kunmap_flush_on_unmap()

Matthew Wilcox (Oracle) wrote:
> We already round down the address in kunmap_local_indexed() which is
> the other implementation of __kunmap_local().  The only implementation
> of kunmap_flush_on_unmap() is PA-RISC which is expecting a page-aligned
> address.  This may be causing PA-RISC to be flushing the wrong addresses
> currently.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

> Fixes: 298fa1ad5571 ("highmem: Provide generic variant of kmap_atomic*")
> Cc: stable@...r.kernel.org
> ---
>  include/linux/highmem-internal.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
> index 034b1106d022..e098f38422af 100644
> --- a/include/linux/highmem-internal.h
> +++ b/include/linux/highmem-internal.h
> @@ -200,7 +200,7 @@ static inline void *kmap_local_pfn(unsigned long pfn)
>  static inline void __kunmap_local(const void *addr)
>  {
>  #ifdef ARCH_HAS_FLUSH_ON_KUNMAP
> -	kunmap_flush_on_unmap(addr);
> +	kunmap_flush_on_unmap(PTR_ALIGN_DOWN(addr, PAGE_SIZE));
>  #endif
>  }
>  
> @@ -227,7 +227,7 @@ static inline void *kmap_atomic_pfn(unsigned long pfn)
>  static inline void __kunmap_atomic(const void *addr)
>  {
>  #ifdef ARCH_HAS_FLUSH_ON_KUNMAP
> -	kunmap_flush_on_unmap(addr);
> +	kunmap_flush_on_unmap(PTR_ALIGN_DOWN(addr, PAGE_SIZE));
>  #endif
>  	pagefault_enable();
>  	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -- 
> 2.35.1
>