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diff --git a/scsi/rz_disk_bbr.c b/scsi/rz_disk_bbr.c
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+/* 
+ * Mach Operating System
+ * Copyright (c) 1991,1990 Carnegie Mellon University
+ * All Rights Reserved.
+ * 
+ * Permission to use, copy, modify and distribute this software and its
+ * documentation is hereby granted, provided that both the copyright
+ * notice and this permission notice appear in all copies of the
+ * software, derivative works or modified versions, and any portions
+ * thereof, and that both notices appear in supporting documentation.
+ * 
+ * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
+ * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
+ * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
+ * 
+ * Carnegie Mellon requests users of this software to return to
+ * 
+ *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
+ *  School of Computer Science
+ *  Carnegie Mellon University
+ *  Pittsburgh PA 15213-3890
+ * 
+ * any improvements or extensions that they make and grant Carnegie Mellon
+ * the rights to redistribute these changes.
+ */
+/*
+ *	File: rz_disk_bbr.c
+ * 	Author: Alessandro Forin, Carnegie Mellon University
+ *	Date:	4/91
+ *
+ *	Top layer of the SCSI driver: interface with the MI.
+ *	This file contains bad-block management functions
+ *	(retry, replace) for disk-like devices.
+ */
+
+#include <mach/std_types.h>
+#include <scsi/compat_30.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_defs.h>
+#include <scsi/rz.h>
+
+#if  (NSCSI > 0)
+
+int	scsi_bbr_retries = 10;
+
+#define	BBR_ACTION_COMPLETE	1
+#define	BBR_ACTION_RETRY_READ	2
+#define BBR_ACTION_REASSIGN	3
+#define	BBR_ACTION_COPY		4
+#define	BBR_ACTION_VERIFY	5
+
+static void make_msf(); /* forward */
+
+/*
+ * Bad block replacement routine, invoked on
+ * unrecovereable disk read/write errors.
+ */
+boolean_t
+scdisk_bad_block_repl(tgt, blockno)
+	target_info_t		*tgt;
+	unsigned int		blockno;
+{
+	register io_req_t	ior = tgt->ior;
+
+	if (scsi_no_automatic_bbr || (ior->io_op & IO_INTERNAL))
+		return FALSE;
+
+	/* signal we took over */
+	tgt->flags |= TGT_BBR_ACTIVE;
+
+	printf("%s", "Attempting bad block replacement..");
+
+	tgt->dev_info.disk.b.badblockno = blockno;
+	tgt->dev_info.disk.b.retry_count = 0;
+
+	tgt->dev_info.disk.b.save_rec   = ior->io_recnum;
+	tgt->dev_info.disk.b.save_addr  = ior->io_data;
+	tgt->dev_info.disk.b.save_count = ior->io_count;
+	tgt->dev_info.disk.b.save_resid = ior->io_residual;
+
+	/*
+	 * On a write all we need is to rewire the offending block.
+	 * Note that the sense data identified precisely which 512 sector
+	 * is bad.  At the end we'll retry the entire write, so if there
+	 * is more than one bad sector involved they will be handled one
+	 * at a time.
+	 */
+	if ((ior->io_op & IO_READ) == 0) {
+		char msf[sizeof(int)];
+		ior->io_temporary = BBR_ACTION_COMPLETE;
+		printf("%s", "just reassign..");
+		make_msf(msf,blockno);
+		scsi_reassign_blocks( tgt, msf, 1, ior);
+	} else
+	/*
+	 * This is more complicated.  We asked for N bytes, and somewhere
+	 * in there there is a chunk of bad data.  First off, we should retry
+	 * at least a couple of times to retrieve that data [yes the drive
+	 * should have done its best already so what].  If that fails we
+	 * should recover as much good data as possible (before the bad one).
+	 */
+	{
+		ior->io_temporary = BBR_ACTION_RETRY_READ;
+		printf("%s", "retry read..");
+		ior->io_residual = 0;
+		scdisk_start_rw(tgt, ior);
+	}
+
+	return TRUE;
+}
+
+static
+void make_msf(buf,val)
+	unsigned char	*buf;
+	unsigned int	val;
+{
+	*buf++ = val >> 24;
+	*buf++ = val >> 16;
+	*buf++ = val >>  8;
+	*buf++ = val >>  0;
+}
+
+/*
+ * This effectively replaces the strategy routine during bbr.
+ */
+void scdisk_bbr_start( tgt, done)
+	target_info_t		*tgt;
+	boolean_t		done;
+{
+	register io_req_t	ior = tgt->ior;
+	char			*msg;
+
+	switch (ior->io_temporary) {
+
+	case BBR_ACTION_COMPLETE:
+
+		/* all done, either way */
+fin:
+		tgt->flags &= ~TGT_BBR_ACTIVE;
+		ior->io_recnum   = tgt->dev_info.disk.b.save_rec;
+		ior->io_data     = tgt->dev_info.disk.b.save_addr;
+		ior->io_count    = tgt->dev_info.disk.b.save_count;
+		ior->io_residual = tgt->dev_info.disk.b.save_resid;
+
+		if (tgt->done == SCSI_RET_SUCCESS) {
+			/* restart normal life */
+			register unsigned int	xferred;
+			if (xferred = ior->io_residual) {
+				ior->io_data -= xferred;
+				ior->io_count += xferred;
+				ior->io_recnum -= xferred / tgt->block_size;
+				ior->io_residual = 0;
+			}
+			/* from the beginning */
+			ior->io_error = 0;
+			msg = "done, restarting.";
+		} else {
+			/* we could not fix it.  Tell user and give up */
+			tgt->ior = ior->io_next;
+			iodone(ior);
+			msg = "done, but could not recover.";
+		}
+
+		printf("%s\n", msg);
+		scdisk_start( tgt, FALSE);
+		return;
+
+	case BBR_ACTION_RETRY_READ:
+
+		/* see if retry worked, if not do it again */
+		if (tgt->done == SCSI_RET_SUCCESS) {
+			char msf[sizeof(int)];
+
+			/* whew, retry worked.  Now rewire that bad block
+			 * and don't forget to copy the good data over */
+
+			tgt->dev_info.disk.b.retry_count = 0;
+			printf("%s", "ok now, reassign..");
+			ior->io_temporary = BBR_ACTION_COPY;
+			make_msf(msf, tgt->dev_info.disk.b.badblockno);
+			scsi_reassign_blocks( tgt, msf, 1, ior);
+			return;
+		}
+		if (tgt->dev_info.disk.b.retry_count++ < scsi_bbr_retries) {
+			scdisk_start_rw( tgt, ior);
+			return;
+		}
+		/* retrying was hopeless. Leave the bad block there for maintainance */
+		/* because we do not know what to write on it */
+		printf("%s%d%s", "failed after ", scsi_bbr_retries, " retries..");
+		goto fin;
+
+
+	case BBR_ACTION_COPY:
+
+		/* retrying succeded and we rewired the bad block. */
+		if (tgt->done == SCSI_RET_SUCCESS) {
+			unsigned int tmp;
+			struct diskpart *label;
+
+			printf("%s", "ok, rewrite..");
+
+			/* writeback only the bad sector */
+
+			/* map blockno back to partition offset */
+/* !!! partition code changes: */
+			tmp = rzpartition(ior->io_unit);
+/*			label=lookup_part(array, tmp +1); */
+			tmp = tgt->dev_info.disk.b.badblockno - 
+/*				label->start; */
+/* #if 0 */
+			      tgt->dev_info.disk.l.d_partitions[tmp].p_offset;
+/* #endif 0 */
+			ior->io_data += (tmp - ior->io_recnum) * tgt->block_size;
+			ior->io_recnum = tmp;
+			ior->io_count = tgt->block_size;
+			ior->io_op &= ~IO_READ;
+
+			ior->io_temporary = BBR_ACTION_VERIFY;
+			scdisk_start_rw( tgt, ior);
+		} else {
+
+			/* either unsupported command, or repl table full */
+			printf("%s", "reassign failed (really needs reformatting), ");
+			ior->io_error = 0;
+			goto fin;
+		}
+		break;
+
+	case BBR_ACTION_VERIFY:
+
+		if (tgt->done == SCSI_RET_SUCCESS) {
+			ior->io_op |= IO_READ;
+			goto fin;
+		}
+
+		if (tgt->dev_info.disk.b.retry_count++ > scsi_bbr_retries) {
+			printf("%s%d%s", "failed after ",
+				scsi_bbr_retries, " retries..");
+			ior->io_op |= IO_READ;
+			goto fin;
+		}
+
+		/* retry, we are *this* close to success.. */
+		scdisk_start_rw( tgt, ior);
+
+		break;
+
+	case BBR_ACTION_REASSIGN:
+
+		/* if we wanted to issue the reassign multiple times */
+		/* XXX unimplemented XXX */
+
+	default:	/* snafu */
+		panic("scdisk_bbr_start");
+	}
+}
+#endif  /* NSCSI > 0 */