[PATCH 8/8] io_uring/zcrx: try to coalesce area pages

[Pavel Begunkov <asml.silence@gmail.com>]

Try to shrink the page array into fewer larger folios if possible. This
reduces the footprint, optimises dma mappings and will be used in the
future for further huge page optimisations.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/zcrx.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 44b5f8084279..9f81682ccf0c 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -166,6 +166,7 @@ static int io_import_umem(struct io_zcrx_ifq *ifq,
 			  struct io_uring_zcrx_area_reg *area_reg)
 {
 	unsigned folio_shift = PAGE_SHIFT;
+	struct io_imu_folio_data data;
 	struct scatterlist *sgl;
 	struct page **pages;
 	int nr_pages, ret;
@@ -180,6 +181,17 @@ static int io_import_umem(struct io_zcrx_ifq *ifq,
 	if (IS_ERR(pages))
 		return PTR_ERR(pages);
 
+	if (nr_pages > 1 && io_check_coalesce_buffer(pages, nr_pages, &data)) {
+		/*
+		 * Only coalesce folio addr-aligned pages and when we can
+		 * improve the size.
+		 */
+		if (data.nr_pages_mid != 1 &&
+		    data.nr_pages_head == data.nr_pages_mid &&
+		    io_coalesce_buffer(&pages, &nr_pages, &data))
+			folio_shift = data.folio_shift;
+	}
+
 	ret = sg_alloc_table(&mem->page_sg_table, nr_pages, GFP_KERNEL_ACCOUNT);
 	if (ret)
 		return ret;
-- 
2.49.0