[PATCH net-next v4 3/5] net: devmem: use niov_shift in net_devmem_get_niov_at()

[Stanislav Fomichev <sdf.kernel@gmail.com>]

TX bindings use PAGE_SIZE net_iovs, and the TX lookup hard-codes it.
Derive the index and offset from binding->niov_shift instead, so TX
bindings can use larger net_iovs. No functional change, TX bindings are
still created with PAGE_SHIFT.

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
---
 net/core/devmem.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/core/devmem.c b/net/core/devmem.c
index 5c7d9640e9d1..c6868f39261a 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -581,13 +581,15 @@ struct net_iov *
 net_devmem_get_niov_at(struct net_devmem_dmabuf_binding *binding,
 		       size_t virt_addr, size_t *off, size_t *size)
 {
+	size_t niov_size = 1UL << binding->niov_shift;
+
 	if (virt_addr >= binding->dmabuf->size)
 		return NULL;
 
-	*off = virt_addr % PAGE_SIZE;
-	*size = PAGE_SIZE - *off;
+	*off = virt_addr & (niov_size - 1);
+	*size = niov_size - *off;
 
-	return binding->tx_vec[virt_addr / PAGE_SIZE];
+	return binding->tx_vec[virt_addr >> binding->niov_shift];
 }
 
 /*** "Dmabuf devmem memory provider" ***/
-- 
2.53.0-Meta