linux-kernel - Re: [PATCH 2/3] nios2: Fix flush_dcache

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Date:   Tue, 13 Jun 2023 17:39:09 -0500
From:   Dinh Nguyen <dinguyen@...nel.org>
To:     Helge Deller <deller@....de>, linux@...linux.org.uk,
        linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org
Subject: Re: [PATCH 2/3] nios2: Fix flush_dcache_page() for usage from irq
 context

Hi Helge,

Thanks for the patch. Does it need a Fixes tag?

Dinh

On 5/24/23 10:26, Helge Deller wrote:
> Since at least kernel 6.1, flush_dcache_page() is called with IRQs
> disabled, e.g. from aio_complete().
> 
> But the current implementation for flush_dcache_page() on NIOS2
> unintentionally re-enables IRQs, which may lead to deadlocks.
> 
> Fix it by using xa_lock_irqsave() and xa_unlock_irqrestore()
> for the flush_dcache_mmap_*lock() macros instead.
> 
> Cc: Dinh Nguyen <dinguyen@...nel.org>
> Signed-off-by: Helge Deller <deller@....de>
> ---
>   arch/nios2/include/asm/cacheflush.h | 4 ++++
>   arch/nios2/mm/cacheflush.c          | 5 +++--
>   2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/nios2/include/asm/cacheflush.h b/arch/nios2/include/asm/cacheflush.h
> index d0b71dd71287..a37242662809 100644
> --- a/arch/nios2/include/asm/cacheflush.h
> +++ b/arch/nios2/include/asm/cacheflush.h
> @@ -48,5 +48,9 @@ extern void invalidate_dcache_range(unsigned long start, unsigned long end);
> 
>   #define flush_dcache_mmap_lock(mapping)		xa_lock_irq(&mapping->i_pages)
>   #define flush_dcache_mmap_unlock(mapping)	xa_unlock_irq(&mapping->i_pages)
> +#define flush_dcache_mmap_lock_irqsave(mapping, flags)		\
> +		xa_lock_irqsave(&mapping->i_pages, flags)
> +#define flush_dcache_mmap_unlock_irqrestore(mapping, flags)	\
> +		xa_unlock_irqrestore(&mapping->i_pages, flags)
> 
>   #endif /* _ASM_NIOS2_CACHEFLUSH_H */
> diff --git a/arch/nios2/mm/cacheflush.c b/arch/nios2/mm/cacheflush.c
> index 6aa9257c3ede..35f3b599187f 100644
> --- a/arch/nios2/mm/cacheflush.c
> +++ b/arch/nios2/mm/cacheflush.c
> @@ -75,11 +75,12 @@ static void flush_aliases(struct address_space *mapping, struct page *page)
>   {
>   	struct mm_struct *mm = current->active_mm;
>   	struct vm_area_struct *mpnt;
> +	unsigned long flags;
>   	pgoff_t pgoff;
> 
>   	pgoff = page->index;
> 
> -	flush_dcache_mmap_lock(mapping);
> +	flush_dcache_mmap_lock_irqsave(mapping, flags);
>   	vma_interval_tree_foreach(mpnt, &mapping->i_mmap, pgoff, pgoff) {
>   		unsigned long offset;
> 
> @@ -92,7 +93,7 @@ static void flush_aliases(struct address_space *mapping, struct page *page)
>   		flush_cache_page(mpnt, mpnt->vm_start + offset,
>   			page_to_pfn(page));
>   	}
> -	flush_dcache_mmap_unlock(mapping);
> +	flush_dcache_mmap_unlock_irqrestore(mapping, flags);
>   }
> 
>   void flush_cache_all(void)
> --
> 2.38.1
>