[PATCH] iomap: Add missing flush_dcache_page

[Christoph Hellwig]

On Fri, Jul 16, 2021 at 04:00:32PM +0100, Matthew Wilcox (Oracle) wrote:
> Inline data needs to be flushed from the kernel's view of a page before
> it's mapped by userspace.
> 
> Cc: stable at vger.kernel.org
> Fixes: 19e0c58f6552 ("iomap: generic inline data handling")
> Signed-off-by: Matthew Wilcox (Oracle) <willy at infradead.org>
> ---
>  fs/iomap/buffered-io.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 41da4f14c00b..fe60c603f4ca 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -222,6 +222,7 @@ iomap_read_inline_data(struct inode *inode, struct page *page,
>  	memcpy(addr, iomap->inline_data, size);
>  	memset(addr + size, 0, PAGE_SIZE - size);
>  	kunmap_atomic(addr);
> +	flush_dcache_page(page);

.. and all writes into a kmap also need such a flush, so this needs to
move a line up.  My plan was to add a memcpy_to_page_and_pad helper
ala memcpy_to_page to get various file systems and drivers out of the
business of cache flushing as much as we can.