Ben Hutchings <ben@xxxxxxxxxxxxxxx> writes:
> 3.2.48-rc1 review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Simon Baatz <gmbnomis@xxxxxxxxx>
>
> commit 1bc39742aab09248169ef9d3727c9def3528b3f3 upstream.
Simon suggested Greg not to queue this patch for stable kernels as it
breaks no-MMU ARM configs. He will provide a follow-up patch that
should go together with this one.
Cheers,
--
Luis
>
> Commit f8b63c1 made flush_kernel_dcache_page a no-op assuming that
> the pages it needs to handle are kernel mapped only. However, for
> example when doing direct I/O, pages with user space mappings may
> occur.
>
> Thus, continue to do lazy flushing if there are no user space
> mappings. Otherwise, flush the kernel cache lines directly.
>
> Signed-off-by: Simon Baatz <gmbnomis@xxxxxxxxx>
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> ---
> arch/arm/include/asm/cacheflush.h | 4 +---
> arch/arm/mm/flush.c | 33 +++++++++++++++++++++++++++++++++
> 2 files changed, 34 insertions(+), 3 deletions(-)
>
> --- a/arch/arm/include/asm/cacheflush.h
> +++ b/arch/arm/include/asm/cacheflush.h
> @@ -301,9 +301,7 @@ static inline void flush_anon_page(struc
> }
>
> #define ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE
> -static inline void flush_kernel_dcache_page(struct page *page)
> -{
> -}
> +extern void flush_kernel_dcache_page(struct page *);
>
> #define flush_dcache_mmap_lock(mapping) \
> spin_lock_irq(&(mapping)->tree_lock)
> --- a/arch/arm/mm/flush.c
> +++ b/arch/arm/mm/flush.c
> @@ -304,6 +304,39 @@ void flush_dcache_page(struct page *page
> EXPORT_SYMBOL(flush_dcache_page);
>
> /*
> + * Ensure cache coherency for the kernel mapping of this page. We can
> + * assume that the page is pinned via kmap.
> + *
> + * If the page only exists in the page cache and there are no user
> + * space mappings, this is a no-op since the page was already marked
> + * dirty at creation. Otherwise, we need to flush the dirty kernel
> + * cache lines directly.
> + */
> +void flush_kernel_dcache_page(struct page *page)
> +{
> + if (cache_is_vivt() || cache_is_vipt_aliasing()) {
> + struct address_space *mapping;
> +
> + mapping = page_mapping(page);
> +
> + if (!mapping || mapping_mapped(mapping)) {
> + void *addr;
> +
> + addr = page_address(page);
> + /*
> + * kmap_atomic() doesn't set the page virtual
> + * address for highmem pages, and
> + * kunmap_atomic() takes care of cache
> + * flushing already.
> + */
> + if (!IS_ENABLED(CONFIG_HIGHMEM) || addr)
> + __cpuc_flush_dcache_area(addr, PAGE_SIZE);
> + }
> + }
> +}
> +EXPORT_SYMBOL(flush_kernel_dcache_page);
> +
> +/*
> * Flush an anonymous page so that users of get_user_pages()
> * can safely access the data. The expected sequence is:
> *
>
> --
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