[PATCH v2 net-next 1/6] ch_ktls: Use memcpy_from_page() instead of k[un]map_atomic()

[Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>]

kmap_atomic() is being deprecated in favor of kmap_local_page(). Replace
the map-memcpy-unmap usage pattern (done using k[un]map_atomic()) with
memcpy_from_page(), which internally uses kmap_local_page() and
kunmap_local(). This renders the variables 'data' and 'vaddr' unnecessary,
and so remove these too.

Note that kmap_atomic() disables preemption and page-fault processing, but
kmap_local_page() doesn't. When converting uses of kmap_atomic(), one has
to check if the code being executed between the map/unmap implicitly
depends on page-faults and/or preemption being disabled. If yes, then code
to disable page-faults and/or preemption should also be added for
functional correctness. That however doesn't appear to be the case here,
so just memcpy_from_page() is used.

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 (via memcpy_from_page()) as opposed to
page_address().

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

Cc: Ayush Sawal <ayush.sawal@chelsio.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
---
v1 -> v2:
 Use memcpy_from_page() as suggested by Fabio
 Add a "Suggested-by" tag
 Rework commit message
 Some emails cc'd in v1 are defunct. Drop them. The MAINTAINERS file for
 Chelsio drivers likely needs an update
---
 .../chelsio/inline_crypto/ch_ktls/chcr_ktls.c | 26 +++++++++----------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c b/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c
index da9973b..1a5fdd7 100644
--- a/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c
+++ b/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c
@@ -1839,9 +1839,7 @@ static int chcr_short_record_handler(struct chcr_ktls_info *tx_info,
 		 */
 		if (prior_data_len) {
 			int i = 0;
-			u8 *data = NULL;
 			skb_frag_t *f;
-			u8 *vaddr;
 			int frag_size = 0, frag_delta = 0;
 
 			while (remaining > 0) {
@@ -1853,24 +1851,24 @@ static int chcr_short_record_handler(struct chcr_ktls_info *tx_info,
 				i++;
 			}
 			f = &record->frags[i];
-			vaddr = kmap_atomic(skb_frag_page(f));
-
-			data = vaddr + skb_frag_off(f)  + remaining;
 			frag_delta = skb_frag_size(f) - remaining;
 
 			if (frag_delta >= prior_data_len) {
-				memcpy(prior_data, data, prior_data_len);
-				kunmap_atomic(vaddr);
+				memcpy_from_page(prior_data, skb_frag_page(f),
+						 skb_frag_off(f) + remaining,
+						 prior_data_len);
 			} else {
-				memcpy(prior_data, data, frag_delta);
-				kunmap_atomic(vaddr);
+				memcpy_from_page(prior_data, skb_frag_page(f),
+						 skb_frag_off(f) + remaining,
+						 frag_delta);
+
 				/* get the next page */
 				f = &record->frags[i + 1];
-				vaddr = kmap_atomic(skb_frag_page(f));
-				data = vaddr + skb_frag_off(f);
-				memcpy(prior_data + frag_delta,
-				       data, (prior_data_len - frag_delta));
-				kunmap_atomic(vaddr);
+
+				memcpy_from_page(prior_data + frag_delta,
+						 skb_frag_page(f),
+						 skb_frag_off(f),
+						 prior_data_len - frag_delta);
 			}
 			/* reset tcp_seq as per the prior_data_required len */
 			tcp_seq -= prior_data_len;
-- 
2.37.2