Initial source

1 files changed, 238 insertions, 0 deletions

diff --git a/device/blkio.c b/device/blkio.c
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+/* 
+ * Mach Operating System
+ * Copyright (c) 1991,1990,1989 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.
+ */
+/*
+ *	Author: David B. Golub, Carnegie Mellon University
+ *	Date: 	7/89
+ *
+ * 	Block IO driven from generic kernel IO interface.
+ */
+#include <mach/kern_return.h>
+
+#include <device/param.h>
+#include <device/device_types.h>
+#include <device/io_req.h>
+#include <device/ds_routines.h>
+
+
+
+io_return_t block_io(strat, max_count, ior)
+	void			(*strat)();
+	void			(*max_count)();
+	register io_req_t	ior;
+{
+	register kern_return_t	rc;
+	boolean_t		wait = FALSE;
+
+	/*
+	 * Make sure the size is not too large by letting max_count
+	 * change io_count.  If we are doing a write, then io_alloc_size
+	 * preserves the original io_count.
+	 */
+	(*max_count)(ior);
+
+	/*
+	 * If reading, allocate memory.  If writing, wire
+	 * down the incoming memory.
+	 */
+	if (ior->io_op & IO_READ)
+	    rc = device_read_alloc(ior, (vm_size_t)ior->io_count);
+	else
+	    rc = device_write_get(ior, &wait);
+
+	if (rc != KERN_SUCCESS)
+	    return (rc);
+
+	/*
+	 * Queue the operation for the device.
+	 */
+	(*strat)(ior);
+
+	/*
+	 * The io is now queued.  Wait for it if needed.
+	 */
+	if (wait) {
+		iowait(ior);
+		return(D_SUCCESS);
+	}
+
+	return (D_IO_QUEUED);
+}
+
+/*
+ * 'standard' max_count routine.  VM continuations mean that this
+ * code can cope with arbitrarily-sized write operations (they won't be
+ * atomic, but any caller that cares will do the op synchronously).
+ */
+#define MAX_PHYS        (256 * 1024)
+
+void minphys(ior)
+	register io_req_t	ior;
+{
+	if ((ior->io_op & (IO_WRITE | IO_READ | IO_OPEN)) == IO_WRITE)
+	    return;
+
+        if (ior->io_count > MAX_PHYS)
+            ior->io_count = MAX_PHYS;
+}
+
+/*
+ * Dummy routine placed in device switch entries to indicate that
+ * block device may be mapped.
+ */
+vm_offset_t block_io_mmap()
+{
+	return (0);
+}
+
+/*
+ * Disk sort routine.
+ *
+ * We order the disk request chain so that the disk head will sweep
+ * back and forth across the disk.  The chain is divided into two
+ * pieces, with requests ordered in opposite directions.  Assume that
+ * the first part of the chain holds increasing cylinder numbers.
+ * If a new request has a higher cylinder number than the head of
+ * the chain, the disk head has not yet reached it; the new request
+ * can go in the first part of the chain.  If the new request has
+ * a lower cylinder number, the disk head has already passed it and
+ * must catch it on the way back; so the new request goes in the
+ * second (descending) part of the chain.
+ * When all of the requests in the ascending portion are filled,
+ * the descending chain becomes the first chain, and requests above
+ * the first now go in the second part of the chain (ascending).
+ */
+
+#define	io_cylinder	io_residual
+				/* Disk drivers put cylinder here */
+#define	h_head		io_next
+#define	h_tail		io_prev
+				/* IORs are chained here */
+
+void disksort(head, ior)
+	io_req_t	head;	/* (sort of) */
+	io_req_t	ior;
+{
+	register int		cylinder = ior->io_cylinder;
+	register io_req_t	next, prev;
+
+	next = head->h_head;
+	if (next == 0) {
+	    head->h_head = ior;
+	    head->h_tail = ior;
+	    ior->io_next = 0;
+	    return;
+	}
+
+	do {
+	    prev = next;
+	    next = prev->io_next;
+	} while (next != 0 && prev->io_cylinder == next->io_cylinder);
+
+	if (next == 0) {
+	    prev->io_next = ior;
+	    head->h_tail = ior;
+	    ior->io_next = 0;
+	    return;
+	}
+
+	if (prev->io_cylinder < next->io_cylinder) {
+	    /*
+	     * Ascending list first.
+	     */
+	    if (prev->io_cylinder <= cylinder) {
+		/*
+		 * Insert in ascending list.
+		 */
+		while (next != 0 &&
+			next->io_cylinder <= cylinder &&
+			prev->io_cylinder <= next->io_cylinder)
+		{
+		    prev = next;
+		    next = prev->io_next;
+		}
+	    }
+	    else {
+		/*
+		 * Insert in descending list
+		 */
+		do {
+		    prev = next;
+		    next = prev->io_next;
+		} while (next != 0 &&
+			prev->io_cylinder <= next->io_cylinder);
+
+		while (next != 0 &&
+			next->io_cylinder >= cylinder)
+		{
+		    prev = next;
+		    next = prev->io_next;
+		}
+	    }
+	}
+	else {
+	    /*
+	     * Descending first.
+	     */
+	    if (prev->io_cylinder >= cylinder) {
+		/*
+		 * Insert in descending list.
+		 */
+		while (next != 0 &&
+			next->io_cylinder >= cylinder &&
+			prev->io_cylinder >= next->io_cylinder)
+		{
+		    prev = next;
+		    next = prev->io_next;
+		}
+	    }
+	    else {
+		/*
+		 * Insert in ascending list
+		 */
+		do {
+		    prev = next;
+		    next = prev->io_next;
+		} while (next != 0 &&
+			prev->io_cylinder >= next->io_cylinder);
+		while (next != 0 &&
+			next->io_cylinder <= cylinder)
+		{
+		    prev = next;
+		    next = prev->io_next;
+		}
+	    }
+	}
+	/*
+	 * Insert between prev and next.
+	 */
+	prev->io_next = ior;
+	ior->io_next = next;
+	if (next == 0) {
+	    /* At tail of list. */
+	    head->h_tail = ior;
+	}
+}
+