net: ppp: Reduce GFP_ATOMIC memory usage

100% of the time on stingray, only 1 skb is allocated in the
ppp_async_input loop. Pre-allocate this skb out of atomic context.

Change-Id: Iee2dd42087ea932ced589273f0cd4796711725c7
Signed-off-by: Benoit Goby <benoit@android.com>

diff --git a/drivers/net/ppp_async.c b/drivers/net/ppp_async.c
index af50a530daee25bf3debf8493690861c2ea2fcc2..49ca2493db74207c0b520347e8132a96b2d1356d 100644 (file)
--- a/drivers/net/ppp_async.c
+++ b/drivers/net/ppp_async.c
@@ -100,7 +100,7 @@ static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
 static int ppp_async_push(struct asyncppp *ap);
 static void ppp_async_flush_output(struct asyncppp *ap);
 static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
-                           char *flags, int count);
+                           char *flags, int count, struct sk_buff *skbuf);
 static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
                           unsigned long arg);
 static void ppp_async_process(unsigned long arg);
@@ -344,12 +344,18 @@ ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
                  char *cflags, int count)
 {
        struct asyncppp *ap = ap_get(tty);
+       struct sk_buff *skb;
        unsigned long flags;
 
        if (!ap)
                return;
+
+       skb = __dev_alloc_skb(ap->mru + PPP_HDRLEN + 2, GFP_KERNEL);
+       if (!skb)
+               return;
+
        spin_lock_irqsave(&ap->recv_lock, flags);
-       ppp_async_input(ap, buf, cflags, count);
+       ppp_async_input(ap, buf, cflags, count, skb);
        spin_unlock_irqrestore(&ap->recv_lock, flags);
        if (!skb_queue_empty(&ap->rqueue))
                tasklet_schedule(&ap->tsk);
@@ -831,7 +837,7 @@ process_input_packet(struct asyncppp *ap)
 
 static void
 ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
-               char *flags, int count)
+               char *flags, int count, struct sk_buff *skbuf)
 {
        struct sk_buff *skb;
        int c, i, j, n, s, f;
@@ -873,9 +879,14 @@ ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
                        /* stuff the chars in the skb */
                        skb = ap->rpkt;
                        if (!skb) {
-                               skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
-                               if (!skb)
-                                       goto nomem;
+                               if (skbuf) {
+                                       skb = skbuf;
+                                       skbuf = NULL;
+                               } else {
+                                       skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
+                                       if (!skb)
+                                               goto nomem;
+                               }
                                ap->rpkt = skb;
                        }
                        if (skb->len == 0) {
@@ -925,11 +936,13 @@ ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
                        flags += n;
                count -= n;
        }
+       kfree(skbuf);
        return;
 
  nomem:
        printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
        ap->state |= SC_TOSS;
+       kfree(skbuf);
 }
 
 /*