netdev - [PATCH net-next 4/5] cassini: Use kmap_local_page() instead of kmap

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Message-Id: <20221117222557.2196195-5-anirudh.venkataramanan@intel.com>
Date:   Thu, 17 Nov 2022 14:25:56 -0800
From:   Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>
To:     netdev@...r.kernel.org
Cc:     Ira Weiny <ira.weiny@...el.com>,
        "Fabio M . De Francesco" <fmdefrancesco@...il.com>,
        Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>
Subject: [PATCH net-next 4/5] cassini: Use kmap_local_page() instead of kmap_atomic()

kmap_atomic() is being deprecated in favor of kmap_local_page().
Replace kmap_atomic() and kunmap_atomic() with kmap_local_page() and
kunmap_local() respectively. cas_page_map() and cas_page_unmap() aren't
really useful anymore, so get rid of these as well.

Note that kmap_atomic() disables preemption and page-fault processing,
but kmap_local_page() doesn't. Converting the former to the latter is safe
only if there isn't an implicit dependency on preemption and page-fault
handling being disabled, which does appear to be the case here.

Also note that the page being mapped is not allocated by the driver,
and so the driver doesn't know if the page is in normal memory. This is the
reason kmap_local_page() is used as opposed to page_address().

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

Cc: Ira Weiny <ira.weiny@...el.com>
Cc: Fabio M. De Francesco <fmdefrancesco@...il.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>
---
 drivers/net/ethernet/sun/cassini.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/sun/cassini.c b/drivers/net/ethernet/sun/cassini.c
index 2f66cfc..3e632b0 100644
--- a/drivers/net/ethernet/sun/cassini.c
+++ b/drivers/net/ethernet/sun/cassini.c
@@ -90,8 +90,6 @@
 #include <linux/uaccess.h>
 #include <linux/jiffies.h>

-#define cas_page_map(x)      kmap_atomic((x))
-#define cas_page_unmap(x)    kunmap_atomic((x))
 #define CAS_NCPUS            num_online_cpus()

 #define cas_skb_release(x)  netif_rx(x)
@@ -2788,11 +2786,11 @@ static inline int cas_xmit_tx_ringN(struct cas *cp, int ring,
 				      ctrl, 0);
 			entry = TX_DESC_NEXT(ring, entry);

-			addr = cas_page_map(skb_frag_page(fragp));
+			addr = kmap_local_page(skb_frag_page(fragp));
 			memcpy(tx_tiny_buf(cp, ring, entry),
 			       addr + skb_frag_off(fragp) + len - tabort,
 			       tabort);
-			cas_page_unmap(addr);
+			kunmap_local(addr);
 			mapping = tx_tiny_map(cp, ring, entry, tentry);
 			len     = tabort;
 		}
-- 
2.37.2