f_phonet: use page-sized rather than MTU-sized RX buffers

Instead of a large (physically) linear buffer, we generate a set of
paged sk_buff, so no extra memory copy is involved. This removes
high-order allocations and saves quite a bit of memory. Phonet MTU is
65541 bytes, so the two buffers were padded to 128 kilo-bytes each.
Now, we create 17 page buffers, almost a 75% memory use reduction.

Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 51 insertions, 26 deletions

diff --git a/drivers/usb/gadget/f_phonet.c b/drivers/usb/gadget/f_phonet.c
index f4eff7ca0d36..d2de10b9dc4b 100644
--- a/drivers/usb/gadget/f_phonet.c
+++ b/drivers/usb/gadget/f_phonet.c
@@ -35,6 +35,10 @@
 #include "u_phonet.h"
 
 #define PN_MEDIA_USB    0x1B
+#define MAXPACKET       512
+#if (PAGE_SIZE % MAXPACKET)
+#error MAXPACKET must divide PAGE_SIZE!
+#endif
 
 /*-------------------------------------------------------------------------*/
 
@@ -45,6 +49,10 @@ struct phonet_port {
 
 struct f_phonet {
         struct usb_function             function;
+        struct {
+                struct sk_buff          *skb;
+                spinlock_t              lock;
+        } rx;
         struct net_device               *dev;
         struct usb_ep                   *in_ep, *out_ep;
 
@@ -52,7 +60,7 @@ struct f_phonet {
         struct usb_request              *out_reqv[0];
 };
 
-static int phonet_rxq_size = 2;
+static int phonet_rxq_size = 17;
 
 static inline struct f_phonet *func_to_pn(struct usb_function *f)
 {
@@ -138,7 +146,7 @@ pn_hs_sink_desc = {
 
         .bEndpointAddress =     USB_DIR_OUT,
         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
-        .wMaxPacketSize =       cpu_to_le16(512),
+        .wMaxPacketSize =       cpu_to_le16(MAXPACKET),
 };
 
 static struct usb_endpoint_descriptor
@@ -298,21 +306,21 @@ static void pn_net_setup(struct net_device *dev)
 static int
 pn_rx_submit(struct f_phonet *fp, struct usb_request *req, gfp_t gfp_flags)
 {
-        struct sk_buff *skb;
-        const size_t size = fp->dev->mtu;
+        struct net_device *dev = fp->dev;
+        struct page *page;
         int err;
 
-        skb = alloc_skb(size, gfp_flags);
-        if (!skb)
+        page = __netdev_alloc_page(dev, gfp_flags);
+        if (!page)
                 return -ENOMEM;
 
-        req->buf = skb->data;
-        req->length = size;
-        req->context = skb;
+        req->buf = page_address(page);
+        req->length = PAGE_SIZE;
+        req->context = page;
 
         err = usb_ep_queue(fp->out_ep, req, gfp_flags);
         if (unlikely(err))
-                dev_kfree_skb_any(skb);
+                netdev_free_page(dev, page);
         return err;
 }
 
@@ -320,25 +328,37 @@ static void pn_rx_complete(struct usb_ep *ep, struct usb_request *req)
 {
         struct f_phonet *fp = ep->driver_data;
         struct net_device *dev = fp->dev;
-        struct sk_buff *skb = req->context;
+        struct page *page = req->context;
+        struct sk_buff *skb;
+        unsigned long flags;
         int status = req->status;
 
         switch (status) {
         case 0:
-                if (unlikely(!netif_running(dev)))
-                        break;
-                if (unlikely(req->actual < 1))
+                spin_lock_irqsave(&fp->rx.lock, flags);
+                skb = fp->rx.skb;
+                if (!skb)
+                        skb = fp->rx.skb = netdev_alloc_skb(dev, 12);
+                if (req->actual < req->length) /* Last fragment */
+                        fp->rx.skb = NULL;
+                spin_unlock_irqrestore(&fp->rx.lock, flags);
+
+                if (unlikely(!skb))
                         break;
-                skb_put(skb, req->actual);
-                skb->protocol = htons(ETH_P_PHONET);
-                skb_reset_mac_header(skb);
-                __skb_pull(skb, 1);
-                skb->dev = dev;
-                dev->stats.rx_packets++;
-                dev->stats.rx_bytes += skb->len;
-
-                netif_rx(skb);
-                skb = NULL;
+                skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, 0,
+                                req->actual);
+                page = NULL;
+
+                if (req->actual < req->length) { /* Last fragment */
+                        skb->protocol = htons(ETH_P_PHONET);
+                        skb_reset_mac_header(skb);
+                        pskb_pull(skb, 1);
+                        skb->dev = dev;
+                        dev->stats.rx_packets++;
+                        dev->stats.rx_bytes += skb->len;
+
+                        netif_rx(skb);
+                }
                 break;
 
         /* Do not resubmit in these cases: */
@@ -356,8 +376,8 @@ static void pn_rx_complete(struct usb_ep *ep, struct usb_request *req)
                 break;
         }
 
-        if (skb)
-                dev_kfree_skb_any(skb);
+        if (page)
+                netdev_free_page(dev, page);
         if (req)
                 pn_rx_submit(fp, req, GFP_ATOMIC);
 }
@@ -375,6 +395,10 @@ static void __pn_reset(struct usb_function *f)
 
         usb_ep_disable(fp->out_ep);
         usb_ep_disable(fp->in_ep);
+        if (fp->rx.skb) {
+                dev_kfree_skb_irq(fp->rx.skb);
+                fp->rx.skb = NULL;
+        }
 }
 
 static int pn_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
@@ -573,6 +597,7 @@ int __init phonet_bind_config(struct usb_configuration *c)
         fp->function.set_alt = pn_set_alt;
         fp->function.get_alt = pn_get_alt;
         fp->function.disable = pn_disconnect;
+        spin_lock_init(&fp->rx.lock);
 
         err = usb_add_function(c, &fp->function);
         if (err)