PERFORCE change 113762 for review

[Robert Watson]

http://perforce.freebsd.org/chv.cgi?CH=113762

Change 113762 by rwatson at rwatson_cinnamon on 2007/01/31 14:50:13

	When in BPF immediate mode, modify getznext to rotate the buffers
	if there is data in the stored buffer but not the held buffer:
	this is effectively the same behavior found in bpfread(), and
	causes a BPF buffer rotation if it can satisfy the request for a
	buffer immediately by doing so.
	
	Move the BPF rotation logic [back] into the global include file
	so that bpf_zerocopy.c can use it.

Affected files ...

.. //depot/projects/zcopybpf/src/sys/net/bpf.c#8 edit
.. //depot/projects/zcopybpf/src/sys/net/bpf.h#4 edit
.. //depot/projects/zcopybpf/src/sys/net/bpf_zerocopy.c#7 edit

Differences ...

==== //depot/projects/zcopybpf/src/sys/net/bpf.c#8 (text+ko) ====

@@ -613,19 +613,6 @@
 }
 
 /*
- * Rotate the packet buffers in descriptor d.  Move the store buffer into
- * the hold slot, and the free buffer ino the store slot.  Zero the length of
- * the new store buffer.  Descriptor lock should be held.
- */
-#define	ROTATE_BUFFERS(d)	do {					\
-	(d)->bd_hbuf = (d)->bd_sbuf;					\
-	(d)->bd_hlen = (d)->bd_slen;					\
-	(d)->bd_sbuf = (d)->bd_fbuf;					\
-	(d)->bd_slen = 0;						\
-	(d)->bd_fbuf = NULL;						\
-} while (0)
-
-/*
  *  bpfread - read next chunk of packets from buffers
  */
 static	int

==== //depot/projects/zcopybpf/src/sys/net/bpf.h#4 (text+ko) ====

@@ -663,6 +663,19 @@
 #endif
 
 /*
+ * Rotate the packet buffers in descriptor d.  Move the store buffer into the
+ * hold slot, and the free buffer ino the store slot.  Zero the length of the
+ * new store buffer.  Descriptor lock should be held.
+ */
+#define	ROTATE_BUFFERS(d)	do {					\
+	(d)->bd_hbuf = (d)->bd_sbuf;					\
+	(d)->bd_hlen = (d)->bd_slen;					\
+	(d)->bd_sbuf = (d)->bd_fbuf;					\
+	(d)->bd_slen = 0;						\
+	(d)->bd_fbuf = NULL;						\
+} while (0)
+
+/*
  * Descriptor associated with each attached hardware interface.
  */
 struct bpf_if {

==== //depot/projects/zcopybpf/src/sys/net/bpf_zerocopy.c#7 (text+ko) ====

@@ -480,9 +480,10 @@
 }
 
 /*
- * Ioctl to return the next completed buffer to read, if any.  Only the first
- * pointer/length in the zbuf are used, since at most one buffer is in the
- * hold position on the descriptor.
+ * Ioctl to return the next completed buffer to read, if any.  In immediate
+ * mode, this may force a buffer rotation if there is stored data but no held
+ * data, in similar style to calling bpfread() on an immediate mode
+ * descriptor.
  */
 int
 bpf_zerocopy_ioctl_getznext(struct thread *td, struct bpf_d *d,
@@ -496,7 +497,14 @@
 	// printf("bpf_zerocopy_ioctl_getznext(td: %p, pid: %d, d: %p)\n", td,
 	//     td->td_proc->p_pid, d);
 
+	/*
+	 * If in immediate mode, there's no holder buffer, but there is
+	 * stored packet data, rotate so that the stored buffer is now the
+	 * held buffer.
+	 */
 	BPFD_LOCK(d);
+	if (d->bd_immediate && d->bd_hbuf == NULL && d->bd_slen != 0)
+		ROTATE_BUFFERS(d);
 	bzero(bz, sizeof(*bz));
 	if (d->bd_hbuf != NULL) {
 		zb = (struct zbuf *)d->bd_hbuf;