From b55a81d93991dbc0f8d6852310b1466e9591d5cd Mon Sep 17 00:00:00 2001
From: Theo de Raadt <deraadt@cvs.openbsd.org>
Date: Tue, 26 May 2020 13:38:08 +0000
Subject: iodcstrategy() maintains a cache for READ performance (tapes are
 supported here, and alternatively would need to rewind).  WRITE code exists,
 but was always wrong -- it writes the cache-buffer to disk, rather than the
 provided write-buffer.  Copy the write-buffer into the cache, and invalidate
 the cache completely so that future reads start from scratch.

---
 sys/arch/hppa/stand/libsa/pdc.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

(limited to 'sys')

diff --git a/sys/arch/hppa/stand/libsa/pdc.c b/sys/arch/hppa/stand/libsa/pdc.c
index 7ab9abbbd4e..6926e1ab001 100644
--- a/sys/arch/hppa/stand/libsa/pdc.c
+++ b/sys/arch/hppa/stand/libsa/pdc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pdc.c,v 1.21 2013/03/23 16:08:28 deraadt Exp $	*/
+/*	$OpenBSD: pdc.c,v 1.22 2020/05/26 13:38:07 deraadt Exp $	*/
 
 /*
  * Copyright (c) 1998-2004 Michael Shalayeff
@@ -201,8 +201,9 @@ iodcstrategy(devdata, rw, blk, size, buf, rsize)
 	}
 
 	xfer = 0;
-	/* see if we can scratch anything from buffer */
-	if (dp->last_blk <= blk && (dp->last_blk + dp->last_read) > blk) {
+	/* On read, see if we can scratch anything from buffer */
+	if (rw == F_READ &&
+	    dp->last_blk <= blk && (dp->last_blk + dp->last_read) > blk) {
 		twiddle();
 		offset = blk - dp->last_blk;
 		xfer = min(dp->last_read - offset, size);
@@ -222,6 +223,12 @@ iodcstrategy(devdata, rw, blk, size, buf, rsize)
 	 */
 	for (; size; size -= ret, buf += ret, blk += ret, xfer += ret) {
 		offset = blk & IOPGOFSET;
+		if (rw != F_READ) {
+			/* put block into cache, but invalidate cache */
+			bcopy(buf, dp->buf, size);
+			dp->last_blk = 0;
+			dp->last_read = 0;
+		}
 		if ((ret = ((iodcio_t)pzdev->pz_iodc_io)(pzdev->pz_hpa,
 		    (rw == F_READ? IODC_IO_READ: IODC_IO_WRITE),
 		    pzdev->pz_spa, pzdev->pz_layers, pdcbuf,
@@ -238,11 +245,13 @@ iodcstrategy(devdata, rw, blk, size, buf, rsize)
 		}
 		if ((ret = pdcbuf[0]) <= 0)
 			break;
-		dp->last_blk = blk - offset;
-		dp->last_read = ret;
-		if ((ret -= offset) > size)
-			ret = size;
-		bcopy(dp->buf + offset, buf, ret);
+		if (rw == F_READ) {
+			dp->last_blk = blk - offset;
+			dp->last_read = ret;
+			if ((ret -= offset) > size)
+				ret = size;
+			bcopy(dp->buf + offset, buf, ret);
+		}
 #ifdef PDCDEBUG
 		if (debug)
 			printf("read %d(%d,%d)@%x ", ret,
-- 
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