- Add a B_ORDERED flag to communicate to drivers that an I/O request should
be issued/completed in order; that is, provide a barrier for I/O queues. - Change the buffer driver queue links to a TAILQ, rather than using a home-grown equivalent. Provide BUFQ_*() macros to manipulate buffer queues; these deal with the barrier provided by B_ORDERED. - Update disksort() accordingly, and provide 3 versions: - disksort_cylinder(): historical disksort(), which keys on b_cylinder (and b_blkno for the case when b_cylinder matches). - disksort_blkno(): sorts only on b_blkno. Essentially the same as disksort_cylinder(), but with fewer comparisons. - disksort_tail(): requests are simply inserted into the queue at the tail. This is provided as an option so that drivers can simply have a pointer to the appropriate sort function. Note that disksort() now pays attention to B_ORDERED.
This commit is contained in:
thorpej
parent
9c658d828e
commit
05c6b5a9a0
@ -1,7 +1,7 @@
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/* $NetBSD: subr_disk.c,v 1.25 1999/02/22 16:00:01 drochner Exp $ */
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/* $NetBSD: subr_disk.c,v 1.26 2000/01/21 23:20:51 thorpej Exp $ */
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/*-
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* Copyright (c) 1996, 1997 The NetBSD Foundation, Inc.
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* Copyright (c) 1996, 1997, 1999, 2000 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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@ -98,28 +98,40 @@ int disk_count; /* number of drives in global disklist */
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* Seek sort for disks. We depend on the driver which calls us using b_resid
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* as the current cylinder number.
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*
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* The argument ap structure holds a b_actf activity chain pointer on which we
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* keep two queues, sorted in ascending cylinder order. The first queue holds
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* those requests which are positioned after the current cylinder (in the first
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* request); the second holds requests which came in after their cylinder number
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* was passed. Thus we implement a one way scan, retracting after reaching the
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* end of the drive to the first request on the second queue, at which time it
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* becomes the first queue.
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* The argument bufq is an I/O queue for the device, on which there are
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* actually two queues, sorted in ascending cylinder order. The first
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* queue holds those requests which are positioned after the current
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* cylinder (in the first request); the second holds requests which came
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* in after their cylinder number was passed. Thus we implement a one-way
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* scan, retracting after reaching the end of the drive to the first request
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* on the second queue, at which time it becomes the first queue.
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*
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* A one-way scan is natural because of the way UNIX read-ahead blocks are
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* allocated.
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*
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* This is further adjusted by any `barriers' which may exist in the queue.
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* The bufq points to the last such ordered request.
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*/
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void
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disksort(ap, bp)
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register struct buf *ap, *bp;
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disksort_cylinder(bufq, bp)
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struct buf_queue *bufq;
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struct buf *bp;
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{
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register struct buf *bq;
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struct buf *bq, *nbq;
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/* If the queue is empty, then it's easy. */
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if (ap->b_actf == NULL) {
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bp->b_actf = NULL;
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ap->b_actf = bp;
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/*
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* If there are ordered requests on the queue, we must start
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* the elevator sort after the last of these.
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*/
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if ((bq = bufq->bq_barrier) == NULL)
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bq = BUFQ_FIRST(bufq);
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/*
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* If the queue is empty, of if it's an ordered request,
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* it's easy; we just go on the end.
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*/
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if (bq == NULL || (bp->b_flags & B_ORDERED) != 0) {
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BUFQ_INSERT_TAIL(bufq, bp);
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return;
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}
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@ -127,15 +139,14 @@ disksort(ap, bp)
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* If we lie after the first (currently active) request, then we
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* must locate the second request list and add ourselves to it.
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*/
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bq = ap->b_actf;
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if (bp->b_cylinder < bq->b_cylinder) {
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while (bq->b_actf) {
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while ((nbq = BUFQ_NEXT(bq)) != NULL) {
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/*
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* Check for an ``inversion'' in the normally ascending
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* cylinder numbers, indicating the start of the second
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* request list.
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*/
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if (bq->b_actf->b_cylinder < bq->b_cylinder) {
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if (nbq->b_cylinder < bq->b_cylinder) {
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/*
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* Search the second request list for the first
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* request at a larger cylinder number. We go
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@ -143,18 +154,16 @@ disksort(ap, bp)
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* go at end.
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*/
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do {
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if (bp->b_cylinder <
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bq->b_actf->b_cylinder)
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if (bp->b_cylinder < nbq->b_cylinder)
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goto insert;
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if (bp->b_cylinder ==
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bq->b_actf->b_cylinder &&
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bp->b_blkno < bq->b_actf->b_blkno)
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if (bp->b_cylinder == nbq->b_cylinder &&
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bp->b_blkno < nbq->b_blkno)
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goto insert;
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bq = bq->b_actf;
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} while (bq->b_actf);
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bq = nbq;
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} while ((nbq = BUFQ_NEXT(bq)) != NULL);
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goto insert; /* after last */
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}
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bq = bq->b_actf;
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bq = BUFQ_NEXT(bq);
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}
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/*
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* No inversions... we will go after the last, and
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@ -166,26 +175,134 @@ disksort(ap, bp)
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* Request is at/after the current request...
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* sort in the first request list.
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*/
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while (bq->b_actf) {
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while ((nbq = BUFQ_NEXT(bq)) != NULL) {
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/*
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* We want to go after the current request if there is an
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* inversion after it (i.e. it is the end of the first
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* request list), or if the next request is a larger cylinder
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* than our request.
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*/
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if (bq->b_actf->b_cylinder < bq->b_cylinder ||
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bp->b_cylinder < bq->b_actf->b_cylinder ||
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(bp->b_cylinder == bq->b_actf->b_cylinder &&
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bp->b_blkno < bq->b_actf->b_blkno))
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if (nbq->b_cylinder < bq->b_cylinder ||
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bp->b_cylinder < nbq->b_cylinder ||
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(bp->b_cylinder == nbq->b_cylinder &&
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bp->b_blkno < nbq->b_blkno))
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goto insert;
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bq = bq->b_actf;
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bq = nbq;
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}
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/*
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* Neither a second list nor a larger request... we go at the end of
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* the first list, which is the same as the end of the whole schebang.
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*/
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insert: bp->b_actf = bq->b_actf;
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bq->b_actf = bp;
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insert: BUFQ_INSERT_AFTER(bufq, bq, bp);
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}
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/*
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* Seek sort for disks. This version sorts based on b_blkno, which
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* indicates the block number.
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*
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* As before, there are actually two queues, sorted in ascendening block
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* order. The first queue holds those requests which are positioned after
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* the current block (in the first request); the second holds requests which
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* came in after their block number was passed. Thus we implement a one-way
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* scan, retracting after reaching the end of the driver to the first request
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* on the second queue, at which time it becomes the first queue.
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*
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* A one-way scan is natural because of the way UNIX read-ahead blocks are
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* allocated.
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*
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* This is further adjusted by any `barriers' which may exist in the queue.
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* The bufq points to the last such ordered request.
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*/
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void
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disksort_blkno(bufq, bp)
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struct buf_queue *bufq;
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struct buf *bp;
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{
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struct buf *bq, *nbq;
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/*
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* If there are ordered requests on the queue, we must start
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* the elevator sort after the last of these.
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*/
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if ((bq = bufq->bq_barrier) == NULL)
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bq = BUFQ_FIRST(bufq);
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/*
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* If the queue is empty, or if it's an ordered request,
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* it's easy; we just go on the end.
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*/
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if (bq == NULL || (bp->b_flags & B_ORDERED) != 0) {
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BUFQ_INSERT_TAIL(bufq, bp);
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return;
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}
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/*
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* If we lie after the first (currently active) request, then we
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* must locate the second request list and add ourselves to it.
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*/
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if (bp->b_blkno < bq->b_blkno) {
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while ((nbq = BUFQ_NEXT(bq)) != NULL) {
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/*
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* Check for an ``inversion'' in the normally ascending
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* block numbers, indicating the start of the second
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* request list.
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*/
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if (nbq->b_blkno < bq->b_blkno) {
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/*
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* Search the second request list for the first
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* request at a larger block number. We go
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* after that; if there is no such request, we
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* go at the end.
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*/
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do {
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if (bp->b_blkno < nbq->b_blkno)
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goto insert;
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bq = nbq;
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} while ((nbq = BUFQ_NEXT(bq)) != NULL);
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goto insert; /* after last */
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}
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bq = BUFQ_NEXT(bq);
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}
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/*
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* No inversions... we will go after the last, and
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* be the first request in the second request list.
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*/
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goto insert;
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}
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/*
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* Request is at/after the current request...
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* sort in the first request list.
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*/
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while ((nbq = BUFQ_NEXT(bq)) != NULL) {
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/*
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* We want to go after the current request if there is an
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* inversion after it (i.e. it is the end of the first
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* request list), or if the next request is a larger cylinder
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* than our request.
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*/
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if (nbq->b_blkno < bq->b_blkno ||
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bp->b_blkno < nbq->b_blkno)
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goto insert;
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bq = nbq;
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}
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/*
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* Neither a second list nor a larger request... we go at the end of
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* the first list, which is the same as the end of the whole schebang.
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*/
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insert: BUFQ_INSERT_AFTER(bufq, bq, bp);
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}
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/*
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* Seek non-sort for disks. This version simply inserts requests at
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* the tail of the queue.
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*/
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void
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disksort_tail(bufq, bp)
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struct buf_queue *bufq;
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struct buf *bp;
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{
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BUFQ_INSERT_TAIL(bufq, bp);
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}
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/*
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100
sys/sys/buf.h
100
sys/sys/buf.h
@ -1,4 +1,41 @@
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/* $NetBSD: buf.h,v 1.35 1999/11/15 18:49:12 fvdl Exp $ */
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/* $NetBSD: buf.h,v 1.36 2000/01/21 23:20:51 thorpej Exp $ */
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/*-
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* Copyright (c) 1999, 2000 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
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* NASA Ames Research Center.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Copyright (c) 1982, 1986, 1989, 1993
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@ -51,6 +88,54 @@
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* To avoid including <ufs/ffs/softdep.h>
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*/
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LIST_HEAD(workhead, worklist);
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/*
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* Device driver buffer queue.
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*/
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struct buf_queue {
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TAILQ_HEAD(bufq_head, buf) bq_head; /* actual list of buffers */
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struct buf *bq_barrier; /* last B_ORDERED request */
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};
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#ifdef _KERNEL
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#define BUFQ_FIRST(bufq) TAILQ_FIRST(&(bufq)->bq_head)
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#define BUFQ_NEXT(bp) TAILQ_NEXT((bp), b_actq)
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#define BUFQ_INIT(bufq) \
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do { \
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TAILQ_INIT(&(bufq)->bq_head); \
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(bufq)->bq_barrier = NULL; \
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} while (/*CONSTCOND*/0)
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#define BUFQ_INSERT_TAIL(bufq, bp) \
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do { \
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TAILQ_INSERT_TAIL(&(bufq)->bq_head, (bp), b_actq); \
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if (((bp)->b_flags & B_ORDERED) != 0) \
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(bufq)->bq_barrier = (bp); \
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} while (/*CONSTCOND*/0)
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#define BUFQ_INSERT_AFTER(bufq, lbp, bp) \
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do { \
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KASSERT((bufq)->bq_barrier == NULL); \
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KASSERT(((bp)->b_flags & B_ORDERED) == 0); \
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TAILQ_INSERT_AFTER(&(bufq)->bq_head, (lbp), (bp), b_actq); \
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} while (/*CONSTCOND*/0)
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#define BUFQ_INSERT_BEFORE(bufq, lbp, bp) \
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do { \
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KASSERT((bufq)->bq_barrier == NULL); \
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KASSERT(((bp)->b_flags & B_ORDERED) == 0); \
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TAILQ_INSERT_BEFORE((lbp), (bp), b_actq); \
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} while (/*CONSTCOND*/0)
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#define BUFQ_REMOVE(bufq, bp) \
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do { \
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if ((bufq)->bq_barrier == (bp)) \
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(bufq)->bq_barrier = TAILQ_PREV((bp), bufq_head, b_actq); \
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TAILQ_REMOVE(&(bufq)->bq_head, (bp), b_actq); \
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} while (/*CONSTCOND*/0)
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#endif /* _KERNEL */
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/*
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* These are currently used only by the soft dependency code, hence
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* are stored once in a global variable. If other subsystems wanted
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@ -75,7 +160,7 @@ struct buf {
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LIST_ENTRY(buf) b_hash; /* Hash chain. */
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LIST_ENTRY(buf) b_vnbufs; /* Buffer's associated vnode. */
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TAILQ_ENTRY(buf) b_freelist; /* Free list position if not active. */
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struct buf *b_actf, **b_actb; /* Device driver queue when active. */
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TAILQ_ENTRY(buf) b_actq; /* Device driver queue when active. */
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struct proc *b_proc; /* Associated proc; NULL if kernel. */
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volatile long b_flags; /* B_* flags. */
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int b_error; /* Errno value. */
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||||
@ -109,11 +194,7 @@ struct buf {
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#define b_cylinder b_resid /* Cylinder number for disksort(). */
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/* Device driver compatibility definitions. */
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#define b_active b_bcount /* Driver queue head: drive active. */
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#define b_data b_un.b_addr /* b_un.b_addr is not changeable. */
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#define b_errcnt b_resid /* Retry count while I/O in progress. */
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#define iodone biodone /* Old name for biodone. */
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#define iowait biowait /* Old name for biowait. */
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/*
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* These flags are kept in b_flags.
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||||
@ -134,6 +215,7 @@ struct buf {
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#define B_INVAL 0x00002000 /* Does not contain valid info. */
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#define B_LOCKED 0x00004000 /* Locked in core (not reusable). */
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#define B_NOCACHE 0x00008000 /* Do not cache block after use. */
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#define B_ORDERED 0x00010000 /* ordered I/O request */
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#define B_PHYS 0x00040000 /* I/O to user memory. */
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||||
#define B_RAW 0x00080000 /* Set by physio for raw transfers. */
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||||
#define B_READ 0x00100000 /* Read buffer. */
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||||
@ -161,10 +243,11 @@ struct cluster_save {
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/*
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||||
* Zero out the buffer's data area.
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||||
*/
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||||
#define clrbuf(bp) { \
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#define clrbuf(bp) \
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||||
do { \
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memset((bp)->b_data, 0, (u_int)(bp)->b_bcount); \
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||||
(bp)->b_resid = 0; \
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||||
}
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||||
} while (0)
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||||
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||||
/* Flags to low-level allocation routines. */
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||||
#define B_CLRBUF 0x01 /* Request allocated buffer be cleared. */
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||||
@ -180,6 +263,7 @@ extern int nswbuf; /* Number of swap I/O buffer headers. */
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||||
__BEGIN_DECLS
|
||||
void allocbuf __P((struct buf *, int));
|
||||
void bawrite __P((struct buf *));
|
||||
void bowrite __P((struct buf *));
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||||
void bdirty __P((struct buf *));
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||||
void bdwrite __P((struct buf *));
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||||
void biodone __P((struct buf *));
|
||||
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Block a user