ISDN: Use a skb queue instead of open coded solution in isdn_ppp.c

Apart from cleaning up and simplifying the code, this also gets rid of
some cli() and stuff, since skb_queue accesses are atomic via an internal
spinlock.

drivers/isdn/i4l/isdn_ppp.c

@@ -314,8 +314,6 @@ isdn_ppp_open(struct inode *ino, struct file *file)
 	is->maxcid = 16;        /* VJ: maxcid */
 	is->tk = current;
 	init_waitqueue_head(&is->wq);
-	is->first = is->rq + NUM_RCV_BUFFS - 1;	/* receive queue */
-	is->last = is->rq;
 	is->minor = minor;
 #ifdef CONFIG_ISDN_PPP_VJ
 	/*
@@ -337,7 +335,6 @@ static int
 isdn_ppp_release(struct inode *ino, struct file *file)
 {
 	uint minor = minor(ino->i_rdev) - ISDN_MINOR_PPP;
-	int i;
 	struct ippp_struct *is;
 
 	lock_kernel();
@@ -356,14 +353,7 @@ isdn_ppp_release(struct inode *ino, struct file *file)
 		is->state &= ~IPPP_CONNECT;
 		isdn_net_hangup(is->idev);
 	}
-	for (i = 0; i < NUM_RCV_BUFFS; i++) {
-		if (is->rq[i].buf) {
-			kfree(is->rq[i].buf);
-			is->rq[i].buf = NULL;
-		}
-	}
-	is->first = is->rq + NUM_RCV_BUFFS - 1;	/* receive queue */
-	is->last = is->rq;
+	skb_queue_purge(&is->rq);
 
 #ifdef CONFIG_ISDN_PPP_VJ
 /* TODO: if this was the previous master: link the slcomp to the new master */
@@ -595,12 +585,9 @@ static unsigned int
 isdn_ppp_poll(struct file *file, poll_table * wait)
 {
 	unsigned int mask;
-	struct ippp_buf_queue *bf;
-	struct ippp_buf_queue *bl;
 	unsigned long flags;
 	struct ippp_struct *is;
 
-	lock_kernel();
 	is = file->private_data;
 
 	if (is->debug & 0x2)
@@ -622,21 +609,15 @@ isdn_ppp_poll(struct file *file, poll_table * wait)
 	/* we're always ready to send .. */
 	mask = POLLOUT | POLLWRNORM;
 
-	save_flags(flags);
-	cli();
-	bl = is->last;
-	bf = is->first;
 	/*
 	 * if IPPP_NOBLOCK is set we return even if we have nothing to read
 	 */
-	if (bf->next != bl || (is->state & IPPP_NOBLOCK)) {
+	if (!skb_queue_empty(&is->rq) || is->state & IPPP_NOBLOCK) {
 		is->state &= ~IPPP_NOBLOCK;
 		mask |= POLLIN | POLLRDNORM;
 	}
-	restore_flags(flags);
 
  out:
-	unlock_kernel();
 	return mask;
 }
 
@@ -647,10 +628,8 @@ isdn_ppp_poll(struct file *file, poll_table * wait)
 static int
 isdn_ppp_fill_rq(unsigned char *buf, int len, int proto, int slot)
 {
-	struct ippp_buf_queue *bf,
-	*bl;
-	unsigned long flags;
-	unsigned char *nbuf;
+	struct sk_buff *skb;
+	unsigned char *p;
 	struct ippp_struct *is;
 
 	if (slot < 0 || slot >= ISDN_MAX_CHANNELS) {
@@ -663,35 +642,22 @@ isdn_ppp_fill_rq(unsigned char *buf, int len, int proto, int slot)
 		printk(KERN_DEBUG "ippp: device not activated.\n");
 		return 0;
 	}
-	nbuf = (unsigned char *) kmalloc(len + 4, GFP_ATOMIC);
-	if (!nbuf) {
-		printk(KERN_WARNING "ippp: Can't alloc buf\n");
+	if (skb_queue_len(&is->rq) > IPPP_MAX_RQ_LEN) {
+		printk(KERN_WARNING "ippp: Queue is full\n");
 		return 0;
 	}
-	nbuf[0] = PPP_ALLSTATIONS;
-	nbuf[1] = PPP_UI;
-	nbuf[2] = proto >> 8;
-	nbuf[3] = proto & 0xff;
-	memcpy(nbuf + 4, buf, len);
-
-	save_flags(flags);
-	cli();
-
-	bf = is->first;
-	bl = is->last;
-
-	if (bf == bl) {
-		printk(KERN_WARNING "ippp: Queue is full; discarding first buffer\n");
-		bf = bf->next;
-		kfree(bf->buf);
-		is->first = bf;
+	skb = dev_alloc_skb(len + 4);
+	if (!skb) {
+		printk(KERN_WARNING "ippp: Can't alloc buf\n");
+		return 0;
 	}
-	bl->buf = (char *) nbuf;
-	bl->len = len + 4;
-
-	is->last = bl->next;
-	restore_flags(flags);
+	p = skb_put(skb, 4);
+	p += put_u8(p, PPP_ALLSTATIONS);
+	p += put_u8(p, PPP_UI);
+	p += put_u16(p, proto);
+	memcpy(skb_put(skb, len), buf, len);
 
+	skb_queue_tail(&is->rq, skb);
 	wake_up_interruptible(&is->wq);
 
 	return len;
@@ -706,54 +672,36 @@ static ssize_t
 isdn_ppp_read(struct file *file, char *buf, size_t count, loff_t *off)
 {
 	struct ippp_struct *is;
-	struct ippp_buf_queue *b;
-	unsigned long flags;
-	unsigned char *save_buf;
+	struct sk_buff *skb;
 	int retval;
 
 	if (off != &file->f_pos)
 		return -ESPIPE;
 	
-	lock_kernel();
-
 	is = file->private_data;
 
 	if (!(is->state & IPPP_OPEN)) {
 		retval = 0;
 		goto out;
 	}
-	retval = verify_area(VERIFY_WRITE, (void *) buf, count);
-	if (retval)
-		goto out;
-
-	save_flags(flags);
-	cli();
-
-	b = is->first->next;
-	save_buf = b->buf;
-	if (!save_buf) {
-		restore_flags(flags);
+	skb = skb_dequeue(&is->rq);
+	if (!skb) {
 		retval = -EAGAIN;
 		goto out;
 	}
-	if (b->len < count)
-		count = b->len;
-	b->buf = NULL;
-	is->first = b;
-
-	restore_flags(flags);
-
-	if (copy_to_user(buf, save_buf, count)) {
-		kfree(save_buf);
+	if (skb->len > count) {
+		retval = -EMSGSIZE;
+		goto out_free;
+	}
+	if (copy_to_user(buf, skb->data, skb->len)) {
 		retval = -EFAULT;
-		goto out;
+		goto out_free;
 	}
-	kfree(save_buf);
-
-	retval = count;
+	retval = skb->len;
 
+ out_free:
+	dev_kfree_skb(skb);
  out:
-	unlock_kernel();
 	return retval;
 }
 
@@ -881,15 +829,7 @@ isdn_ppp_init(void)
 		}
 		memset((char *) ippp_table[i], 0, sizeof(struct ippp_struct));
 		ippp_table[i]->state = 0;
-		ippp_table[i]->first = ippp_table[i]->rq + NUM_RCV_BUFFS - 1;
-		ippp_table[i]->last = ippp_table[i]->rq;
-
-		for (j = 0; j < NUM_RCV_BUFFS; j++) {
-			ippp_table[i]->rq[j].buf = NULL;
-			ippp_table[i]->rq[j].last = ippp_table[i]->rq +
-			    (NUM_RCV_BUFFS + j - 1) % NUM_RCV_BUFFS;
-			ippp_table[i]->rq[j].next = ippp_table[i]->rq + (j + 1) % NUM_RCV_BUFFS;
-		}
+		skb_queue_head_init(&ippp_table[i]->rq);
 	}
 	return 0;
 }

include/linux/isdn_ppp.h

@@ -159,14 +159,7 @@ typedef struct {
   isdn_mppp_stats stats;
 } ippp_bundle;
 
-#define NUM_RCV_BUFFS     64
-
-struct ippp_buf_queue {
-  struct ippp_buf_queue *next;
-  struct ippp_buf_queue *last;
-  char *buf;                 /* NULL here indicates end of queue */
-  int len;
-};
+#define IPPP_MAX_RQ_LEN     8
 
 /* The data structure for one CCP reset transaction */
 enum ippp_ccp_reset_states {
@@ -201,9 +194,7 @@ struct ippp_ccp_reset {
 struct ippp_struct {
   struct ippp_struct *next_link;
   int state;
-  struct ippp_buf_queue rq[NUM_RCV_BUFFS]; /* packet queue for isdn_ppp_read() */
-  struct ippp_buf_queue *first;  /* pointer to (current) first packet */
-  struct ippp_buf_queue *last;   /* pointer to (current) last used packet in queue */
+  struct sk_buff_head rq;
   wait_queue_head_t wq;
   struct task_struct *tk;
   unsigned int mpppcfg;