initial import of NetBSD tree

1 files changed, 316 insertions, 0 deletions

diff --git a/sys/kern/kern_physio.c b/sys/kern/kern_physio.c
new file mode 100644
index 00000000000..3c8dccec428
--- /dev/null
+++ b/sys/kern/kern_physio.c
@@ -0,0 +1,316 @@
+/*	$NetBSD: kern_physio.c,v 1.25 1995/10/10 02:51:45 mycroft Exp $	*/
+
+/*-
+ * Copyright (c) 1994 Christopher G. Demetriou
+ * Copyright (c) 1982, 1986, 1990, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ * (c) UNIX System Laboratories, Inc.
+ * All or some portions of this file are derived from material licensed
+ * to the University of California by American Telephone and Telegraph
+ * Co. or Unix System Laboratories, Inc. and are reproduced herein with
+ * the permission of UNIX System Laboratories, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)kern_physio.c	8.1 (Berkeley) 6/10/93
+ */
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/buf.h>
+#include <sys/conf.h>
+#include <sys/proc.h>
+
+/*
+ * The routines implemented in this file are described in:
+ *	Leffler, et al.: The Design and Implementation of the 4.3BSD
+ *	    UNIX Operating System (Addison Welley, 1989)
+ * on pages 231-233.
+ *
+ * The routines "getphysbuf" and "putphysbuf" steal and return a swap
+ * buffer.  Leffler, et al., says that swap buffers are used to do the
+ * I/O, so raw I/O requests don't have to be single-threaded.
+ */
+
+struct buf *getphysbuf __P((void));
+void putphysbuf __P((struct buf *bp));
+
+/*
+ * Do "physical I/O" on behalf of a user.  "Physical I/O" is I/O directly
+ * from the raw device to user buffers, and bypasses the buffer cache.
+ *
+ * Comments in brackets are from Leffler, et al.'s pseudo-code implementation.
+ */
+int
+physio(strategy, bp, dev, flags, minphys, uio)
+	void (*strategy) __P((struct buf *));
+	struct buf *bp;
+	dev_t dev;
+	int flags;
+	void (*minphys) __P((struct buf *));
+	struct uio *uio;
+{
+	struct iovec *iovp;
+	struct proc *p = curproc;
+	int error, done, i, nobuf, s, todo;
+
+	error = 0;
+	flags &= B_READ | B_WRITE;
+
+	/*
+	 * [check user read/write access to the data buffer]
+	 *
+	 * Check each iov one by one.  Note that we know if we're reading or
+	 * writing, so we ignore the uio's rw parameter.  Also note that if
+	 * we're doing a read, that's a *write* to user-space.
+	 */
+	for (i = 0; i < uio->uio_iovcnt; i++)
+		if (!useracc(uio->uio_iov[i].iov_base, uio->uio_iov[i].iov_len,
+		    (flags == B_READ) ? B_WRITE : B_READ))
+			return (EFAULT);
+
+	/* Make sure we have a buffer, creating one if necessary. */
+	if (nobuf = (bp == NULL))
+		bp = getphysbuf();
+
+	/* [raise the processor priority level to splbio;] */
+	s = splbio();
+
+	/* [while the buffer is marked busy] */
+	while (bp->b_flags & B_BUSY) {
+		/* [mark the buffer wanted] */
+		bp->b_flags |= B_WANTED;
+		/* [wait until the buffer is available] */
+		tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0);
+	}
+
+	/* Mark it busy, so nobody else will use it. */
+	bp->b_flags |= B_BUSY;
+
+	/* [lower the priority level] */
+	splx(s);
+
+	/* [set up the fixed part of the buffer for a transfer] */
+	bp->b_dev = dev;
+	bp->b_error = 0;
+	bp->b_proc = p;
+
+	/*
+	 * [while there are data to transfer and no I/O error]
+	 * Note that I/O errors are handled with a 'goto' at the bottom
+	 * of the 'while' loop.
+	 */
+	for (i = 0; i < uio->uio_iovcnt; i++) {
+		iovp = &uio->uio_iov[i];
+		while (iovp->iov_len > 0) {
+			/*
+			 * [mark the buffer busy for physical I/O]
+			 * (i.e. set B_PHYS (because it's an I/O to user
+			 * memory, and B_RAW, because B_RAW is to be
+			 * "Set by physio for raw transfers.", in addition
+			 * to the "busy" and read/write flag.)
+			 */
+			bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags;
+
+			/* [set up the buffer for a maximum-sized transfer] */
+			bp->b_blkno = btodb(uio->uio_offset);
+			bp->b_bcount = iovp->iov_len;
+			bp->b_data = iovp->iov_base;
+
+			/*
+			 * [call minphys to bound the tranfer size]
+			 * and remember the amount of data to transfer,
+			 * for later comparison.
+			 */
+			(*minphys)(bp);
+			todo = bp->b_bcount;
+#ifdef DIAGNOSTIC
+			if (todo < 0)
+				panic("todo < 0; minphys broken");
+			if (todo > MAXPHYS)
+				panic("todo > MAXPHYS; minphys broken");
+#endif
+
+			/*
+			 * [lock the part of the user address space involved
+			 *    in the transfer]
+			 * Beware vmapbuf(); it clobbers b_data and
+			 * saves it in b_saveaddr.  However, vunmapbuf()
+			 * restores it.
+			 */
+			p->p_holdcnt++;
+			vslock(bp->b_data, todo);
+			vmapbuf(bp, todo);
+
+			/* [call strategy to start the transfer] */
+			(*strategy)(bp);
+
+			/*
+			 * Note that the raise/wait/lower/get error
+			 * steps below would be done by biowait(), but
+			 * we want to unlock the address space before
+			 * we lower the priority.
+			 *
+			 * [raise the priority level to splbio]
+			 */
+			s = splbio();
+
+			/* [wait for the transfer to complete] */
+			while ((bp->b_flags & B_DONE) == 0)
+				tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0);
+
+			/* Mark it busy again, so nobody else will use it. */
+			bp->b_flags |= B_BUSY;
+
+			/* [lower the priority level] */
+			splx(s);
+
+			/*
+			 * [unlock the part of the address space previously
+			 *    locked]
+			 */
+			vunmapbuf(bp, todo);
+			vsunlock(bp->b_data, todo);
+			p->p_holdcnt--;
+
+			/* remember error value (save a splbio/splx pair) */
+			if (bp->b_flags & B_ERROR)
+				error = (bp->b_error ? bp->b_error : EIO);
+
+			/*
+			 * [deduct the transfer size from the total number
+			 *    of data to transfer]
+			 */
+			done = bp->b_bcount - bp->b_resid;
+#ifdef DIAGNOSTIC
+			if (done < 0)
+				panic("done < 0; strategy broken");
+			if (done > todo)
+				panic("done > todo; strategy broken");
+#endif
+			iovp->iov_len -= done;
+                        iovp->iov_base += done;
+                        uio->uio_offset += done;
+                        uio->uio_resid -= done;
+
+			/*
+			 * Now, check for an error.
+			 * Also, handle weird end-of-disk semantics.
+			 */
+			if (error || done < todo)
+				goto done;
+		}
+	}
+
+done:
+	/*
+	 * [clean up the state of the buffer]
+	 * Remember if somebody wants it, so we can wake them up below.
+	 * Also, if we had to steal it, give it back.
+	 */
+	s = splbio();
+	bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW);
+	if (nobuf)
+		putphysbuf(bp);
+	else {
+		/*
+		 * [if another process is waiting for the raw I/O buffer,
+		 *    wake up processes waiting to do physical I/O;
+		 */
+		if (bp->b_flags & B_WANTED) {
+			bp->b_flags &= ~B_WANTED;
+			wakeup(bp);
+		}
+	}
+	splx(s);
+
+	return (error);
+}
+
+/*
+ * Get a swap buffer structure, for use in physical I/O.
+ * Mostly taken from /sys/vm/swap_pager.c, except that it no longer
+ * records buffer list-empty conditions, and sleeps at PRIBIO + 1,
+ * rather than PSWP + 1 (and on a different wchan).
+ */
+struct buf *
+getphysbuf()
+{
+	struct buf *bp;
+	int s;
+
+	s = splbio();
+        while (bswlist.b_actf == NULL) {
+                bswlist.b_flags |= B_WANTED;
+                tsleep((caddr_t)&bswlist, PRIBIO + 1, "getphys", 0);
+        }
+        bp = bswlist.b_actf;
+        bswlist.b_actf = bp->b_actf;
+        splx(s);
+	return (bp);
+}
+
+/*
+ * Get rid of a swap buffer structure which has been used in physical I/O.
+ * Mostly taken from /sys/vm/swap_pager.c, except that it now uses
+ * wakeup() rather than the VM-internal thread_wakeup(), and that the caller
+ * must mask disk interrupts, rather than putphysbuf() itself.
+ */
+void
+putphysbuf(bp)
+	struct buf *bp;
+{
+
+        bp->b_actf = bswlist.b_actf;
+        bswlist.b_actf = bp;
+        if (bp->b_vp)
+                brelvp(bp);
+        if (bswlist.b_flags & B_WANTED) {
+                bswlist.b_flags &= ~B_WANTED;
+                wakeup(&bswlist);
+        }
+}
+
+/*
+ * Leffler, et al., says on p. 231:
+ * "The minphys() routine is called by physio() to adjust the
+ * size of each I/O transfer before the latter is passed to
+ * the strategy routine..."
+ *
+ * so, just adjust the buffer's count accounting to MAXPHYS here,
+ * and return the new count;
+ */
+void
+minphys(bp)
+	struct buf *bp;
+{
+
+	if (bp->b_bcount > MAXPHYS)
+		bp->b_bcount = MAXPHYS;
+}