Re: [PATCH v2] fs/aio: Replace kmap{,_atomic}() with kmap_local_page()

[Al Viro]

On Mon, Jan 09, 2023 at 06:56:29PM +0100, Fabio M. De Francesco wrote:

> -	ring = kmap_atomic(ctx->ring_pages[0]);
> +	ring = kmap_local_page(ctx->ring_pages[0]);
>  	ring->nr = nr_events;	/* user copy */
>  	ring->id = ~0U;
>  	ring->head = ring->tail = 0;
> @@ -575,7 +575,7 @@ static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
>  	ring->compat_features = AIO_RING_COMPAT_FEATURES;
>  	ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
>  	ring->header_length = sizeof(struct aio_ring);
> -	kunmap_atomic(ring);
> +	kunmap_local(ring);
>  	flush_dcache_page(ctx->ring_pages[0]);

I wonder if it would be more readable as memcpy_to_page(), actually...
>  
>  	return 0;
> @@ -678,9 +678,9 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
>  					 * we are protected from page migration
>  					 * changes ring_pages by ->ring_lock.
>  					 */
> -					ring = kmap_atomic(ctx->ring_pages[0]);
> +					ring = kmap_local_page(ctx->ring_pages[0]);
>  					ring->id = ctx->id;
> -					kunmap_atomic(ring);
> +					kunmap_local(ring);

Incidentally, does it need flush_dcache_page()?