Revert "isdn: isdn_ppp: Use SKB list facilities instead of home-grown implementation."

This reverts commit 38783e67.

It causes kernel bugzilla #14594
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/i4l/isdn_ppp.c

@@ -1535,10 +1535,8 @@ static int isdn_ppp_mp_bundle_array_init(void)
 	int sz = ISDN_MAX_CHANNELS*sizeof(ippp_bundle);
 	if( (isdn_ppp_bundle_arr = kzalloc(sz, GFP_KERNEL)) == NULL )
 		return -ENOMEM;
-	for (i = 0; i < ISDN_MAX_CHANNELS; i++) {
+	for( i = 0; i < ISDN_MAX_CHANNELS; i++ )
 		spin_lock_init(&isdn_ppp_bundle_arr[i].lock);
-		skb_queue_head_init(&isdn_ppp_bundle_arr[i].frags);
-	}
 	return 0;
 }
 
@@ -1571,7 +1569,7 @@ static int isdn_ppp_mp_init( isdn_net_local * lp, ippp_bundle * add_to )
 		if ((lp->netdev->pb = isdn_ppp_mp_bundle_alloc()) == NULL)
 			return -ENOMEM;
 		lp->next = lp->last = lp;	/* nobody else in a queue */
-		skb_queue_head_init(&lp->netdev->pb->frags);
+		lp->netdev->pb->frags = NULL;
 		lp->netdev->pb->frames = 0;
 		lp->netdev->pb->seq = UINT_MAX;
 	}
@@ -1583,24 +1581,23 @@ static int isdn_ppp_mp_init( isdn_net_local * lp, ippp_bundle * add_to )
 
 static u32 isdn_ppp_mp_get_seq( int short_seq, 
 					struct sk_buff * skb, u32 last_seq );
-static void isdn_ppp_mp_discard(ippp_bundle *mp, struct sk_buff *from,
-				struct sk_buff *to);
-static void isdn_ppp_mp_reassembly(isdn_net_dev *net_dev, isdn_net_local *lp,
-				   struct sk_buff *from, struct sk_buff *to,
-				   u32 lastseq);
-static void isdn_ppp_mp_free_skb(ippp_bundle *mp, struct sk_buff *skb);
+static struct sk_buff * isdn_ppp_mp_discard( ippp_bundle * mp,
+			struct sk_buff * from, struct sk_buff * to );
+static void isdn_ppp_mp_reassembly( isdn_net_dev * net_dev, isdn_net_local * lp,
+				struct sk_buff * from, struct sk_buff * to );
+static void isdn_ppp_mp_free_skb( ippp_bundle * mp, struct sk_buff * skb );
 static void isdn_ppp_mp_print_recv_pkt( int slot, struct sk_buff * skb );
 
 static void isdn_ppp_mp_receive(isdn_net_dev * net_dev, isdn_net_local * lp, 
 							struct sk_buff *skb)
 {
-	struct sk_buff *newfrag, *frag, *start, *nextf;
-	u32 newseq, minseq, thisseq;
-	isdn_mppp_stats *stats;
 	struct ippp_struct *is;
+	isdn_net_local * lpq;
+	ippp_bundle * mp;
+	isdn_mppp_stats * stats;
+	struct sk_buff * newfrag, * frag, * start, *nextf;
+	u32 newseq, minseq, thisseq;
 	unsigned long flags;
-	isdn_net_local *lpq;
-	ippp_bundle *mp;
 	int slot;
 
 	spin_lock_irqsave(&net_dev->pb->lock, flags);
@@ -1616,7 +1613,7 @@ static void isdn_ppp_mp_receive(isdn_net_dev * net_dev, isdn_net_local * lp,
 		return;
 	}
 	is = ippp_table[slot];
-	if (++mp->frames > stats->max_queue_len)
+    	if( ++mp->frames > stats->max_queue_len )
 		stats->max_queue_len = mp->frames;
 	
 	if (is->debug & 0x8)
@@ -1625,10 +1622,11 @@ static void isdn_ppp_mp_receive(isdn_net_dev * net_dev, isdn_net_local * lp,
 	newseq = isdn_ppp_mp_get_seq(is->mpppcfg & SC_IN_SHORT_SEQ, 
 						skb, is->last_link_seqno);
 
+
 	/* if this packet seq # is less than last already processed one,
 	 * toss it right away, but check for sequence start case first 
 	 */
-	if (mp->seq > MP_LONGSEQ_MAX && (newseq & MP_LONGSEQ_MAXBIT)) {
+	if( mp->seq > MP_LONGSEQ_MAX && (newseq & MP_LONGSEQ_MAXBIT) ) {
 		mp->seq = newseq;	/* the first packet: required for
 					 * rfc1990 non-compliant clients --
 					 * prevents constant packet toss */
@@ -1659,31 +1657,22 @@ static void isdn_ppp_mp_receive(isdn_net_dev * net_dev, isdn_net_local * lp,
 					 * packets */
 	newfrag = skb;
 
-	/* Insert new fragment into the proper sequence slot.  */
-	skb_queue_walk(&mp->frags, frag) {
-		if (MP_SEQ(frag) == newseq) {
-			isdn_ppp_mp_free_skb(mp, newfrag);
+  	/* if this new fragment is before the first one, then enqueue it now. */
+  	if ((frag = mp->frags) == NULL || MP_LT(newseq, MP_SEQ(frag))) {
+		newfrag->next = frag;
+    		mp->frags = frag = newfrag;
     		newfrag = NULL;
-			break;
   	}
-		if (MP_LT(newseq, MP_SEQ(frag))) {
-			__skb_queue_before(&mp->frags, frag, newfrag);
-			newfrag = NULL;
-			break;
-		}
-	}
-	if (newfrag)
-		__skb_queue_tail(&mp->frags, newfrag);
 
-	frag = skb_peek(&mp->frags);
-	start = ((MP_FLAGS(frag) & MP_BEGIN_FRAG) &&
-		 (MP_SEQ(frag) == mp->seq)) ? frag : NULL;
-	if (!start)
-		goto check_overflow;
+  	start = MP_FLAGS(frag) & MP_BEGIN_FRAG &&
+				MP_SEQ(frag) == mp->seq ? frag : NULL;
 
-	/* main fragment traversing loop
+	/* 
+	 * main fragment traversing loop
 	 *
 	 * try to accomplish several tasks:
+	 * - insert new fragment into the proper sequence slot (once that's done
+	 *   newfrag will be set to NULL)
 	 * - reassemble any complete fragment sequence (non-null 'start'
 	 *   indicates there is a continguous sequence present)
 	 * - discard any incomplete sequences that are below minseq -- due
@@ -1692,45 +1681,70 @@ static void isdn_ppp_mp_receive(isdn_net_dev * net_dev, isdn_net_local * lp,
 	 *   come to complete such sequence and it should be discarded
 	 *
 	 * loop completes when we accomplished the following tasks:
+	 * - new fragment is inserted in the proper sequence ('newfrag' is 
+	 *   set to NULL)
 	 * - we hit a gap in the sequence, so no reassembly/processing is 
 	 *   possible ('start' would be set to NULL)
 	 *
 	 * algorithm for this code is derived from code in the book
 	 * 'PPP Design And Debugging' by James Carlson (Addison-Wesley)
 	 */
-	skb_queue_walk_safe(&mp->frags, frag, nextf) {
+  	while (start != NULL || newfrag != NULL) {
+
     		thisseq = MP_SEQ(frag);
+    		nextf = frag->next;
+
+    		/* drop any duplicate fragments */
+    		if (newfrag != NULL && thisseq == newseq) {
+      			isdn_ppp_mp_free_skb(mp, newfrag);
+      			newfrag = NULL;
+    		}
 
+    		/* insert new fragment before next element if possible. */
+    		if (newfrag != NULL && (nextf == NULL || 
+						MP_LT(newseq, MP_SEQ(nextf)))) {
+      			newfrag->next = nextf;
+      			frag->next = nextf = newfrag;
+      			newfrag = NULL;
+    		}
+
+    		if (start != NULL) {
 	    		/* check for misplaced start */
       			if (start != frag && (MP_FLAGS(frag) & MP_BEGIN_FRAG)) {
 				printk(KERN_WARNING"isdn_mppp(seq %d): new "
 				      "BEGIN flag with no prior END", thisseq);
 				stats->seqerrs++;
 				stats->frame_drops++;
-			isdn_ppp_mp_discard(mp, start, frag);
-			start = frag;
+				start = isdn_ppp_mp_discard(mp, start,frag);
+				nextf = frag->next;
+      			}
     		} else if (MP_LE(thisseq, minseq)) {		
       			if (MP_FLAGS(frag) & MP_BEGIN_FRAG)
 				start = frag;
       			else {
 				if (MP_FLAGS(frag) & MP_END_FRAG)
 	  				stats->frame_drops++;
-				__skb_unlink(skb, &mp->frags);
+				if( mp->frags == frag )
+					mp->frags = nextf;	
 				isdn_ppp_mp_free_skb(mp, frag);
+				frag = nextf;
 				continue;
       			}
 		}
 		
-		/* if we have end fragment, then we have full reassembly
-		 * sequence -- reassemble and process packet now
+		/* if start is non-null and we have end fragment, then
+		 * we have full reassembly sequence -- reassemble 
+		 * and process packet now
 		 */
-		if (MP_FLAGS(frag) & MP_END_FRAG) {
+    		if (start != NULL && (MP_FLAGS(frag) & MP_END_FRAG)) {
       			minseq = mp->seq = (thisseq+1) & MP_LONGSEQ_MASK;
       			/* Reassemble the packet then dispatch it */
-			isdn_ppp_mp_reassembly(net_dev, lp, start, frag, thisseq);
+			isdn_ppp_mp_reassembly(net_dev, lp, start, nextf);
       
       			start = NULL;
       			frag = NULL;
+
+      			mp->frags = nextf;
     		}
 
 		/* check if need to update start pointer: if we just
@@ -1742,24 +1756,25 @@ static void isdn_ppp_mp_receive(isdn_net_dev * net_dev, isdn_net_local * lp,
 		 * below low watermark and set start to the next frag or
 		 * clear start ptr.
 		 */ 
-		if (nextf != (struct sk_buff *)&mp->frags && 
+    		if (nextf != NULL && 
 		    ((thisseq+1) & MP_LONGSEQ_MASK) == MP_SEQ(nextf)) {
       			/* if we just reassembled and the next one is here, 
-			 * then start another reassembly.
-			 */
+			 * then start another reassembly. */
+
       			if (frag == NULL) {
 				if (MP_FLAGS(nextf) & MP_BEGIN_FRAG)
 	  				start = nextf;
-				else {
+				else
+				{
 	  				printk(KERN_WARNING"isdn_mppp(seq %d):"
 						" END flag with no following "
 						"BEGIN", thisseq);
 					stats->seqerrs++;
 				}
 			}
+
     		} else {
-			if (nextf != (struct sk_buff *)&mp->frags &&
-			    frag != NULL &&
+			if ( nextf != NULL && frag != NULL &&
 						MP_LT(thisseq, minseq)) {
 				/* we've got a break in the sequence
 				 * and we not at the end yet
@@ -1769,39 +1784,41 @@ static void isdn_ppp_mp_receive(isdn_net_dev * net_dev, isdn_net_local * lp,
 			 	 * discard all the frames below low watermark 
 				 * and start over */
 				stats->frame_drops++;
-				isdn_ppp_mp_discard(mp, start, nextf);
+				mp->frags = isdn_ppp_mp_discard(mp,start,nextf);
 			}
 			/* break in the sequence, no reassembly */
       			start = NULL;
     		}
-		if (!start)
-			break;
-	}
 	  			
-check_overflow:
+    		frag = nextf;
+  	}	/* while -- main loop */
+	
+  	if (mp->frags == NULL)
+    		mp->frags = frag;
+		
 	/* rather straighforward way to deal with (not very) possible 
-	 * queue overflow
-	 */
+	 * queue overflow */
 	if (mp->frames > MP_MAX_QUEUE_LEN) {
 		stats->overflows++;
-		skb_queue_walk_safe(&mp->frags, frag, nextf) {
-			if (mp->frames <= MP_MAX_QUEUE_LEN)
-				break;
-			__skb_unlink(frag, &mp->frags);
-			isdn_ppp_mp_free_skb(mp, frag);
+		while (mp->frames > MP_MAX_QUEUE_LEN) {
+			frag = mp->frags->next;
+			isdn_ppp_mp_free_skb(mp, mp->frags);
+			mp->frags = frag;
 		}
 	}
 	spin_unlock_irqrestore(&mp->lock, flags);
 }
 
-static void isdn_ppp_mp_cleanup(isdn_net_local *lp)
+static void isdn_ppp_mp_cleanup( isdn_net_local * lp )
 {
-	struct sk_buff *skb, *tmp;
-
-	skb_queue_walk_safe(&lp->netdev->pb->frags, skb, tmp) {
-		__skb_unlink(skb, &lp->netdev->pb->frags);
-		isdn_ppp_mp_free_skb(lp->netdev->pb, skb);
-	}
+	struct sk_buff * frag = lp->netdev->pb->frags;
+	struct sk_buff * nextfrag;
+    	while( frag ) {
+		nextfrag = frag->next;
+		isdn_ppp_mp_free_skb(lp->netdev->pb, frag);
+		frag = nextfrag;
+	}
+	lp->netdev->pb->frags = NULL;
 }
 
 static u32 isdn_ppp_mp_get_seq( int short_seq, 
@@ -1838,115 +1855,72 @@ static u32 isdn_ppp_mp_get_seq( int short_seq,
 	return seq;
 }
 
-static void isdn_ppp_mp_discard(ippp_bundle *mp, struct sk_buff *from,
-				struct sk_buff *to)
+struct sk_buff * isdn_ppp_mp_discard( ippp_bundle * mp,
+			struct sk_buff * from, struct sk_buff * to )
 {
-	if (from) {
-		struct sk_buff *skb, *tmp;
-		int freeing = 0;
-
-		skb_queue_walk_safe(&mp->frags, skb, tmp) {
-			if (skb == to)
-				break;
-			if (skb == from)
-				freeing = 1;
-			if (!freeing)
-				continue;
-			__skb_unlink(skb, &mp->frags);
-			isdn_ppp_mp_free_skb(mp, skb);
-		}
-	}
-}
-
-static unsigned int calc_tot_len(struct sk_buff_head *queue,
-				 struct sk_buff *from, struct sk_buff *to)
-{
-	unsigned int tot_len = 0;
-	struct sk_buff *skb;
-	int found_start = 0;
-
-	skb_queue_walk(queue, skb) {
-		if (skb == from)
-			found_start = 1;
-		if (!found_start)
-			continue;
-		tot_len += skb->len - MP_HEADER_LEN;
-		if (skb == to)
-			break;
+	if( from )
+		while (from != to) {
+	  		struct sk_buff * next = from->next;
+			isdn_ppp_mp_free_skb(mp, from);
+	  		from = next;
 		}
-	return tot_len;
+	return from;
 }
 
-/* Reassemble packet using fragments in the reassembly queue from
- * 'from' until 'to', inclusive.
- */
-static void isdn_ppp_mp_reassembly(isdn_net_dev *net_dev, isdn_net_local *lp,
-				   struct sk_buff *from, struct sk_buff *to,
-				   u32 lastseq)
+void isdn_ppp_mp_reassembly( isdn_net_dev * net_dev, isdn_net_local * lp,
+				struct sk_buff * from, struct sk_buff * to )
 {
-	ippp_bundle *mp = net_dev->pb;
-	unsigned int tot_len;
-	struct sk_buff *skb;
+	ippp_bundle * mp = net_dev->pb;
 	int proto;
+	struct sk_buff * skb;
+	unsigned int tot_len;
 
 	if (lp->ppp_slot < 0 || lp->ppp_slot >= ISDN_MAX_CHANNELS) {
 		printk(KERN_ERR "%s: lp->ppp_slot(%d) out of range\n",
 			__func__, lp->ppp_slot);
 		return;
 	}
-
-	tot_len = calc_tot_len(&mp->frags, from, to);
-
-	if (MP_FLAGS(from) == (MP_BEGIN_FRAG | MP_END_FRAG)) {
-		if (ippp_table[lp->ppp_slot]->debug & 0x40)
+	if( MP_FLAGS(from) == (MP_BEGIN_FRAG | MP_END_FRAG) ) {
+		if( ippp_table[lp->ppp_slot]->debug & 0x40 )
 			printk(KERN_DEBUG "isdn_mppp: reassembly: frame %d, "
-			       "len %d\n", MP_SEQ(from), from->len);
+					"len %d\n", MP_SEQ(from), from->len );
 		skb = from;
 		skb_pull(skb, MP_HEADER_LEN);
-		__skb_unlink(skb, &mp->frags);
 		mp->frames--;	
 	} else {
-		struct sk_buff *walk, *tmp;
-		int found_start = 0;
+		struct sk_buff * frag;
+		int n;
 
-		if (ippp_table[lp->ppp_slot]->debug & 0x40)
-			printk(KERN_DEBUG"isdn_mppp: reassembling frames %d "
-			       "to %d, len %d\n", MP_SEQ(from), lastseq,
-			       tot_len);
+		for(tot_len=n=0, frag=from; frag != to; frag=frag->next, n++)
+			tot_len += frag->len - MP_HEADER_LEN;
 
-		skb = dev_alloc_skb(tot_len);
-		if (!skb)
+		if( ippp_table[lp->ppp_slot]->debug & 0x40 )
+			printk(KERN_DEBUG"isdn_mppp: reassembling frames %d "
+				"to %d, len %d\n", MP_SEQ(from), 
+				(MP_SEQ(from)+n-1) & MP_LONGSEQ_MASK, tot_len );
+		if( (skb = dev_alloc_skb(tot_len)) == NULL ) {
 			printk(KERN_ERR "isdn_mppp: cannot allocate sk buff "
 					"of size %d\n", tot_len);
+			isdn_ppp_mp_discard(mp, from, to);
+			return;
+		}
 
-		found_start = 0;
-		skb_queue_walk_safe(&mp->frags, walk, tmp) {
-			if (walk == from)
-				found_start = 1;
-			if (!found_start)
-				continue;
+		while( from != to ) {
+			unsigned int len = from->len - MP_HEADER_LEN;
 
-			if (skb) {
-				unsigned int len = walk->len - MP_HEADER_LEN;
-				skb_copy_from_linear_data_offset(walk, MP_HEADER_LEN,
-								 skb_put(skb, len),
+			skb_copy_from_linear_data_offset(from, MP_HEADER_LEN,
+							 skb_put(skb,len),
 							 len);
-			}
-			__skb_unlink(walk, &mp->frags);
-			isdn_ppp_mp_free_skb(mp, walk);
-
-			if (walk == to)
-				break;
+			frag = from->next;
+			isdn_ppp_mp_free_skb(mp, from);
+			from = frag; 
 		}
 	}
-	if (!skb)
-		return;
-
    	proto = isdn_ppp_strip_proto(skb);
 	isdn_ppp_push_higher(net_dev, lp, skb, proto);
 }
 
-static void isdn_ppp_mp_free_skb(ippp_bundle *mp, struct sk_buff *skb)
+static void isdn_ppp_mp_free_skb(ippp_bundle * mp, struct sk_buff * skb)
 {
 	dev_kfree_skb(skb);
 	mp->frames--;

include/linux/isdn_ppp.h

@@ -157,7 +157,7 @@ typedef struct {
 
 typedef struct {
   int mp_mrru;                        /* unused                             */
-  struct sk_buff_head frags;	/* fragments sl list */
+  struct sk_buff * frags;	/* fragments sl list -- use skb->next */
   long frames;			/* number of frames in the frame list */
   unsigned int seq;		/* last processed packet seq #: any packets
   				 * with smaller seq # will be dropped