netdev - [PATCH net-next 4/6] e1000e: Remove unnecessary use of kmap

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Message-Id: <20221102203957.2944396-5-anthony.l.nguyen@intel.com>
Date:   Wed,  2 Nov 2022 13:39:55 -0700
From:   Tony Nguyen <anthony.l.nguyen@...el.com>
To:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        edumazet@...gle.com
Cc:     Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>,
        netdev@...r.kernel.org, anthony.l.nguyen@...el.com,
        sasha.neftin@...el.com, Ira Weiny <ira.weiny@...el.com>,
        "Fabio M . De Francesco" <fmdefrancesco@...il.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Naama Meir <naamax.meir@...ux.intel.com>
Subject: [PATCH net-next 4/6] e1000e: Remove unnecessary use of kmap_atomic()

From: Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>

alloc_rx_buf() allocates ps_page->page and buffer_info->page using either
GFP_ATOMIC or GFP_KERNEL. Memory allocated with GFP_KERNEL/GFP_ATOMIC can't
come from highmem and so there's no need to kmap() them. Just use
page_address().

I don't have access to a 32-bit system so did some limited testing on qemu
(qemu-system-i386 -m 4096 -smp 4 -device e1000e) with a 32-bit Debian 11.04
image.

Cc: Ira Weiny <ira.weiny@...el.com>
Cc: Fabio M. De Francesco <fmdefrancesco@...il.com>
Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>
Suggested-by: Ira Weiny <ira.weiny@...el.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>
Tested-by: Naama Meir <naamax.meir@...ux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 20 +++++---------------
 1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index f0e015673f48..36bc4fd91ef4 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -1391,26 +1391,18 @@ static bool e1000_clean_rx_irq_ps(struct e1000_ring *rx_ring, int *work_done,
 
 			/* page alloc/put takes too long and effects small
 			 * packet throughput, so unsplit small packets and
-			 * save the alloc/put only valid in softirq (napi)
-			 * context to call kmap_*
+			 * save the alloc/put
 			 */
 			if (l1 && (l1 <= copybreak) &&
 			    ((length + l1) <= adapter->rx_ps_bsize0)) {
-				u8 *vaddr;
-
 				ps_page = &buffer_info->ps_pages[0];
 
-				/* there is no documentation about how to call
-				 * kmap_atomic, so we can't hold the mapping
-				 * very long
-				 */
 				dma_sync_single_for_cpu(&pdev->dev,
 							ps_page->dma,
 							PAGE_SIZE,
 							DMA_FROM_DEVICE);
-				vaddr = kmap_atomic(ps_page->page);
-				memcpy(skb_tail_pointer(skb), vaddr, l1);
-				kunmap_atomic(vaddr);
+				memcpy(skb_tail_pointer(skb),
+				       page_address(ps_page->page), l1);
 				dma_sync_single_for_device(&pdev->dev,
 							   ps_page->dma,
 							   PAGE_SIZE,
@@ -1610,11 +1602,9 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_ring *rx_ring, int *work_done,
 				 */
 				if (length <= copybreak &&
 				    skb_tailroom(skb) >= length) {
-					u8 *vaddr;
-					vaddr = kmap_atomic(buffer_info->page);
-					memcpy(skb_tail_pointer(skb), vaddr,
+					memcpy(skb_tail_pointer(skb),
+					       page_address(buffer_info->page),
 					       length);
-					kunmap_atomic(vaddr);
 					/* re-use the page, so don't erase
 					 * buffer_info->page
 					 */
-- 
2.35.1