Re: [PATCH net-next 3/5] cassini: Remove unnecessary use of kmap_atomic()

On 11/18/2022 12:35 AM, Fabio M. De Francesco wrote:

On giovedì 17 novembre 2022 23:25:55 CET Anirudh Venkataramanan wrote:

quoted

Pages for Rx buffers are allocated in cas_page_alloc() 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() instead.

I don't have hardware, so this change has only been compile tested.

Cc: Ira Weiny <redacted>
Cc: Fabio M. De Francesco <redacted>
Signed-off-by: Anirudh Venkataramanan <redacted>
---
  drivers/net/ethernet/sun/cassini.c | 34 ++++++++++--------------------
  1 file changed, 11 insertions(+), 23 deletions(-)

diff --git a/drivers/net/ethernet/sun/cassini.c

b/drivers/net/ethernet/sun/cassini.c index 0aca193..2f66cfc 100644

--- a/drivers/net/ethernet/sun/cassini.c
+++ b/drivers/net/ethernet/sun/cassini.c

@@ -1915,7 +1915,7 @@ static int cas_rx_process_pkt(struct cas *cp, struct

cas_rx_comp *rxc, int off, swivel = RX_SWIVEL_OFF_VAL;
  	struct cas_page *page;
  	struct sk_buff *skb;
-	void *addr, *crcaddr;
+	void *crcaddr;
  	__sum16 csum;
  	char *p;

@@ -1936,7 +1936,7 @@ static int cas_rx_process_pkt(struct cas *cp, struct

cas_rx_comp *rxc, skb_reserve(skb, swivel);

  	p = skb->data;
-	addr = crcaddr = NULL;
+	crcaddr = NULL;
  	if (hlen) { /* always copy header pages */
  		i = CAS_VAL(RX_COMP2_HDR_INDEX, words[1]);
  		page = cp->rx_pages[CAS_VAL(RX_INDEX_RING, i)]

[CAS_VAL(RX_INDEX_NUM, i)];

quoted

@@ -1948,12 +1948,10 @@ static int cas_rx_process_pkt(struct cas *cp, struct

cas_rx_comp *rxc, i += cp->crc_size;
  		dma_sync_single_for_cpu(&cp->pdev->dev, page->dma_addr +

off,

quoted

  					i, DMA_FROM_DEVICE);
-		addr = cas_page_map(page->buffer);
-		memcpy(p, addr + off, i);
+		memcpy(p, page_address(page->buffer) + off, i);
  		dma_sync_single_for_device(&cp->pdev->dev,
  					   page->dma_addr + off, i,
  					   DMA_FROM_DEVICE);
-		cas_page_unmap(addr);
  		RX_USED_ADD(page, 0x100);
  		p += hlen;
  		swivel = 0;

@@ -1984,12 +1982,11 @@ static int cas_rx_process_pkt(struct cas *cp, struct

cas_rx_comp *rxc, /* make sure we always copy a header */
  		swivel = 0;
  		if (p == (char *) skb->data) { /* not split */
-			addr = cas_page_map(page->buffer);
-			memcpy(p, addr + off, RX_COPY_MIN);
+			memcpy(p, page_address(page->buffer) + off,
+			       RX_COPY_MIN);
  			dma_sync_single_for_device(&cp->pdev->dev,
  						   page->dma_addr

+ off, i,

quoted

DMA_FROM_DEVICE);

quoted

-			cas_page_unmap(addr);
  			off += RX_COPY_MIN;
  			swivel = RX_COPY_MIN;
  			RX_USED_ADD(page, cp->mtu_stride);

@@ -2036,10 +2033,8 @@ static int cas_rx_process_pkt(struct cas *cp, struct

cas_rx_comp *rxc, RX_USED_ADD(page, hlen + cp->crc_size);
  		}

-		if (cp->crc_size) {
-			addr = cas_page_map(page->buffer);
-			crcaddr  = addr + off + hlen;
-		}
+		if (cp->crc_size)
+			crcaddr = page_address(page->buffer) + off +

hlen;

quoted

  	} else {
  		/* copying packet */

@@ -2061,12 +2056,10 @@ static int cas_rx_process_pkt(struct cas *cp, struct

cas_rx_comp *rxc, i += cp->crc_size;
  		dma_sync_single_for_cpu(&cp->pdev->dev, page->dma_addr +

off,

quoted

  					i, DMA_FROM_DEVICE);
-		addr = cas_page_map(page->buffer);
-		memcpy(p, addr + off, i);
+		memcpy(p, page_address(page->buffer) + off, i);
  		dma_sync_single_for_device(&cp->pdev->dev,
  					   page->dma_addr + off, i,
  					   DMA_FROM_DEVICE);
-		cas_page_unmap(addr);
  		if (p == (char *) skb->data) /* not split */
  			RX_USED_ADD(page, cp->mtu_stride);
  		else

@@ -2081,20 +2074,17 @@ static int cas_rx_process_pkt(struct cas *cp, struct

cas_rx_comp *rxc, page->dma_addr,
  						dlen + cp-
crc_size,
  						DMA_FROM_DEVICE);
-			addr = cas_page_map(page->buffer);
-			memcpy(p, addr, dlen + cp->crc_size);
+			memcpy(p, page_address(page->buffer), dlen + cp-
crc_size);
  			dma_sync_single_for_device(&cp->pdev->dev,
  						   page->dma_addr,
  						   dlen + cp-
crc_size,
  						

DMA_FROM_DEVICE);

quoted

-			cas_page_unmap(addr);
  			RX_USED_ADD(page, dlen + cp->crc_size);
  		}
  end_copy_pkt:
-		if (cp->crc_size) {
-			addr    = NULL;
+		if (cp->crc_size)
  			crcaddr = skb->data + alloclen;
-		}
+

This is a different logical change. Some maintainers I met would have asked
for a separate patch, but I'm OK with it being here.

cas_page_map()/cap_page_unmap() were using addr. Once these went away addr became unnecessary. It would be weird to leave the declaration, init and reinit for a variable that's not of any use, and so it was removed as well. It's cleaner this way.

Ani