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

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