3 * The Regents of the University of California. All rights reserved.
4 * Modifications/enhancements:
5 * Copyright (c) 1995 John S. Dyson. All rights reserved.
6 * Copyright (c) 2012-2013 Matthew Dillon. All rights reserved.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 #include "opt_debug_cluster.h"
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/kernel.h>
40 #include <sys/vnode.h>
41 #include <sys/malloc.h>
42 #include <sys/mount.h>
43 #include <sys/resourcevar.h>
44 #include <sys/vmmeter.h>
46 #include <vm/vm_object.h>
47 #include <vm/vm_page.h>
48 #include <sys/sysctl.h>
51 #include <vm/vm_page2.h>
53 #include <machine/limits.h>
56 * Cluster tracking cache - replaces the original vnode v_* fields which had
57 * limited utility and were not MP safe.
59 * The cluster tracking cache is a simple 4-way set-associative non-chained
60 * cache. It is capable of tracking up to four zones separated by 1MB or
63 * NOTE: We want this structure to be cache-line friendly so the iterator
64 * is embedded rather than in a separate array.
66 * NOTE: A cluster cache entry can become stale when a vnode is recycled.
67 * For now we treat the values as heuristical but also self-consistent.
68 * i.e. the values cannot be completely random and cannot be SMP unsafe
69 * or the cluster code might end-up clustering non-contiguous buffers
70 * at the wrong offsets.
72 struct cluster_cache {
75 off_t v_lastw; /* last write (write cluster) */
76 off_t v_cstart; /* start block of cluster */
77 off_t v_lasta; /* last allocation */
78 u_int v_clen; /* length of current cluster */
82 typedef struct cluster_cache cluster_cache_t;
84 #define CLUSTER_CACHE_SIZE 512
85 #define CLUSTER_CACHE_MASK (CLUSTER_CACHE_SIZE - 1)
87 #define CLUSTER_ZONE ((off_t)(1024 * 1024))
89 cluster_cache_t cluster_array[CLUSTER_CACHE_SIZE];
91 #if defined(CLUSTERDEBUG)
92 #include <sys/sysctl.h>
93 static int rcluster= 0;
94 SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0, "");
97 static MALLOC_DEFINE(M_SEGMENT, "cluster_save", "cluster_save buffer");
99 static struct cluster_save *
100 cluster_collectbufs (cluster_cache_t *cc, struct vnode *vp,
101 struct buf *last_bp, int blksize);
103 cluster_rbuild (struct vnode *vp, off_t filesize, off_t loffset,
104 off_t doffset, int blksize, int run,
105 struct buf *fbp, int *srp);
106 static void cluster_callback (struct bio *);
107 static void cluster_setram (struct buf *);
108 static void cluster_clrram (struct buf *);
109 static int cluster_wbuild(struct vnode *vp, struct buf **bpp, int blksize,
110 off_t start_loffset, int bytes);
112 static int write_behind = 1;
113 SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0,
114 "Cluster write-behind setting");
115 static quad_t write_behind_minfilesize = 10 * 1024 * 1024;
116 SYSCTL_QUAD(_vfs, OID_AUTO, write_behind_minfilesize, CTLFLAG_RW,
117 &write_behind_minfilesize, 0, "Cluster write-behind setting");
118 static int max_readahead = 2 * 1024 * 1024;
119 SYSCTL_INT(_vfs, OID_AUTO, max_readahead, CTLFLAG_RW, &max_readahead, 0,
120 "Limit in bytes for desired cluster read-ahead");
122 extern vm_page_t bogus_page;
124 extern int cluster_pbuf_freecnt;
127 * nblks is our cluster_rbuild request size. The approximate number of
128 * physical read-ahead requests is maxra / nblks. The physical request
129 * size is limited by the device (maxrbuild). We also do not want to make
130 * the request size too big or it will mess up the B_RAM streaming.
134 calc_rbuild_reqsize(int maxra, int maxrbuild)
138 if ((nblks = maxra / 4) > maxrbuild)
146 * Acquire/release cluster cache (can return dummy entry)
150 cluster_getcache(cluster_cache_t *dummy, struct vnode *vp, off_t loffset)
157 hv = (size_t)(intptr_t)vp ^ (size_t)(intptr_t)vp / sizeof(*vp);
158 hv &= CLUSTER_CACHE_MASK & ~3;
159 cc = &cluster_array[hv];
162 for (i = 0; i < 4; ++i) {
165 if (((cc[i].v_cstart ^ loffset) & ~(CLUSTER_ZONE - 1)) == 0) {
170 if (xact >= 0 && atomic_swap_int(&cc[xact].locked, 1) == 0) {
171 if (cc[xact].vp == vp &&
172 ((cc[i].v_cstart ^ loffset) & ~(CLUSTER_ZONE - 1)) == 0) {
175 atomic_swap_int(&cc[xact].locked, 0);
179 * New entry. If we can't acquire the cache line then use the
180 * passed-in dummy element and reset all fields.
182 * When we are able to acquire the cache line we only clear the
183 * fields if the vp does not match. This allows us to multi-zone
184 * a vp and for excessive zones / partial clusters to be retired.
186 i = cc->iterator++ & 3;
188 if (atomic_swap_int(&cc->locked, 1) != 0) {
205 cluster_putcache(cluster_cache_t *cc)
207 atomic_swap_int(&cc->locked, 0);
211 * This replaces bread(), providing a synchronous read of the requested
212 * buffer plus asynchronous read-ahead within the specified bounds.
214 * The caller may pre-populate *bpp if it already has the requested buffer
215 * in-hand, else must set *bpp to NULL. Note that the cluster_read() inline
216 * sets *bpp to NULL and then calls cluster_readx() for compatibility.
218 * filesize - read-ahead @ blksize will not cross this boundary
219 * loffset - loffset for returned *bpp
220 * blksize - blocksize for returned *bpp and read-ahead bps
221 * minreq - minimum (not a hard minimum) in bytes, typically reflects
222 * a higher level uio resid.
223 * maxreq - maximum (sequential heuristic) in bytes (highet typ ~2MB)
224 * bpp - return buffer (*bpp) for (loffset,blksize)
227 cluster_readx(struct vnode *vp, off_t filesize, off_t loffset,
228 int blksize, size_t minreq, size_t maxreq, struct buf **bpp)
230 struct buf *bp, *rbp, *reqbp;
242 * Calculate the desired read-ahead in blksize'd blocks (maxra).
243 * To do this we calculate maxreq.
245 * maxreq typically starts out as a sequential heuristic. If the
246 * high level uio/resid is bigger (minreq), we pop maxreq up to
247 * minreq. This represents the case where random I/O is being
248 * performed by the userland is issuing big read()'s.
250 * Then we limit maxreq to max_readahead to ensure it is a reasonable
253 * Finally we must ensure that (loffset + maxreq) does not cross the
254 * boundary (filesize) for the current blocksize. If we allowed it
255 * to cross we could end up with buffers past the boundary with the
256 * wrong block size (HAMMER large-data areas use mixed block sizes).
257 * minreq is also absolutely limited to filesize.
261 /* minreq not used beyond this point */
263 if (maxreq > max_readahead) {
264 maxreq = max_readahead;
265 if (maxreq > 16 * 1024 * 1024)
266 maxreq = 16 * 1024 * 1024;
268 if (maxreq < blksize)
270 if (loffset + maxreq > filesize) {
271 if (loffset > filesize)
274 maxreq = filesize - loffset;
277 maxra = (int)(maxreq / blksize);
280 * Get the requested block.
285 *bpp = reqbp = bp = getblk(vp, loffset, blksize, 0, 0);
286 origoffset = loffset;
289 * Calculate the maximum cluster size for a single I/O, used
290 * by cluster_rbuild().
292 maxrbuild = vmaxiosize(vp) / blksize;
295 * if it is in the cache, then check to see if the reads have been
296 * sequential. If they have, then try some read-ahead, otherwise
297 * back-off on prospective read-aheads.
299 if (bp->b_flags & B_CACHE) {
301 * Not sequential, do not do any read-ahead
307 * No read-ahead mark, do not do any read-ahead
310 if ((bp->b_flags & B_RAM) == 0)
314 * We hit a read-ahead-mark, figure out how much read-ahead
315 * to do (maxra) and where to start (loffset).
317 * Typically the way this works is that B_RAM is set in the
318 * middle of the cluster and triggers an overlapping
319 * read-ahead of 1/2 a cluster more blocks. This ensures
320 * that the cluster read-ahead scales with the read-ahead
321 * count and is thus better-able to absorb the caller's
324 * Estimate where the next unread block will be by assuming
325 * that the B_RAM's are placed at the half-way point.
327 bp->b_flags &= ~B_RAM;
330 rbp = findblk(vp, loffset + i * blksize, FINDBLK_TEST);
331 if (rbp == NULL || (rbp->b_flags & B_CACHE) == 0) {
334 rbp = findblk(vp, loffset + i * blksize,
343 rbp = findblk(vp, loffset + i * blksize,
352 * We got everything or everything is in the cache, no
359 * Calculate where to start the read-ahead and how much
360 * to do. Generally speaking we want to read-ahead by
361 * (maxra) when we've found a read-ahead mark. We do
362 * not want to reduce maxra here as it will cause
363 * successive read-ahead I/O's to be smaller and smaller.
365 * However, we have to make sure we don't break the
366 * filesize limitation for the clustered operation.
368 loffset += i * blksize;
371 if (loffset >= filesize)
373 if (loffset + maxra * blksize > filesize) {
374 maxreq = filesize - loffset;
375 maxra = (int)(maxreq / blksize);
379 * Set RAM on first read-ahead block since we still have
380 * approximate maxra/2 blocks ahead of us that are already
381 * cached or in-progress.
386 * Start block is not valid, we will want to do a
389 __debugvar off_t firstread = bp->b_loffset;
393 * Set-up synchronous read for bp.
395 bp->b_cmd = BUF_CMD_READ;
396 bp->b_bio1.bio_done = biodone_sync;
397 bp->b_bio1.bio_flags |= BIO_SYNC;
399 KASSERT(firstread != NOOFFSET,
400 ("cluster_read: no buffer offset"));
402 nblks = calc_rbuild_reqsize(maxra, maxrbuild);
405 * Set RAM half-way through the full-cluster.
407 sr = (maxra + 1) / 2;
412 error = VOP_BMAP(vp, loffset, &doffset,
413 &burstbytes, NULL, BUF_CMD_READ);
415 goto single_block_read;
416 if (nblks > burstbytes / blksize)
417 nblks = burstbytes / blksize;
418 if (doffset == NOOFFSET)
419 goto single_block_read;
421 goto single_block_read;
423 bp = cluster_rbuild(vp, filesize, loffset,
424 doffset, blksize, nblks, bp, &sr);
425 loffset += bp->b_bufsize;
426 maxra -= bp->b_bufsize / blksize;
430 * If it isn't in the cache, then get a chunk from
431 * disk if sequential, otherwise just get the block.
439 * If B_CACHE was not set issue bp. bp will either be an
440 * asynchronous cluster buf or a synchronous single-buf.
441 * If it is a single buf it will be the same as reqbp.
443 * NOTE: Once an async cluster buf is issued bp becomes invalid.
446 #if defined(CLUSTERDEBUG)
448 kprintf("S(%012jx,%d,%d)\n",
449 (intmax_t)bp->b_loffset, bp->b_bcount, maxra);
451 if ((bp->b_flags & B_CLUSTER) == 0)
452 vfs_busy_pages(vp, bp);
453 bp->b_flags &= ~(B_ERROR|B_INVAL);
454 vn_strategy(vp, &bp->b_bio1);
459 #if defined(CLUSTERDEBUG)
461 kprintf("cluster_rd %016jx/%d maxra=%d sr=%d\n",
462 loffset, blksize, maxra, sr);
466 * If we have been doing sequential I/O, then do some read-ahead.
467 * The code above us should have positioned us at the next likely
470 * Only mess with buffers which we can immediately lock. HAMMER
471 * will do device-readahead irrespective of what the blocks
474 * Set B_RAM on the first buffer (the next likely offset needing
475 * read-ahead), under the assumption that there are still
476 * approximately maxra/2 blocks good ahead of us.
482 rbp = getblk(vp, loffset, blksize,
483 GETBLK_SZMATCH|GETBLK_NOWAIT, 0);
484 #if defined(CLUSTERDEBUG)
486 kprintf("read-ahead %016jx rbp=%p ",
492 if ((rbp->b_flags & B_CACHE)) {
498 * If BMAP is not supported or has an issue, we still do
499 * (maxra) read-ahead, but we do not try to use rbuild.
501 error = VOP_BMAP(vp, loffset, &doffset,
502 &burstbytes, NULL, BUF_CMD_READ);
503 if (error || doffset == NOOFFSET) {
507 nblks = calc_rbuild_reqsize(maxra, maxrbuild);
508 if (nblks > burstbytes / blksize)
509 nblks = burstbytes / blksize;
511 rbp->b_cmd = BUF_CMD_READ;
514 rbp = cluster_rbuild(vp, filesize, loffset,
518 rbp->b_bio2.bio_offset = doffset;
523 rbp->b_flags &= ~(B_ERROR|B_INVAL);
525 if ((rbp->b_flags & B_CLUSTER) == 0)
526 vfs_busy_pages(vp, rbp);
528 loffset += rbp->b_bufsize;
529 maxra -= rbp->b_bufsize / blksize;
530 vn_strategy(vp, &rbp->b_bio1);
531 /* rbp invalid now */
535 * Wait for our original buffer to complete its I/O. reqbp will
536 * be NULL if the original buffer was B_CACHE. We are returning
537 * (*bpp) which is the same as reqbp when reqbp != NULL.
541 KKASSERT(reqbp->b_bio1.bio_flags & BIO_SYNC);
542 error = biowait(&reqbp->b_bio1, "clurd");
550 * This replaces breadcb(), providing an asynchronous read of the requested
551 * buffer with a callback, plus an asynchronous read-ahead within the
554 * The callback must check whether BIO_DONE is set in the bio and issue
555 * the bpdone(bp, 0) if it isn't. The callback is responsible for clearing
556 * BIO_DONE and disposing of the I/O (bqrelse()ing it).
558 * filesize - read-ahead @ blksize will not cross this boundary
559 * loffset - loffset for returned *bpp
560 * blksize - blocksize for returned *bpp and read-ahead bps
561 * minreq - minimum (not a hard minimum) in bytes, typically reflects
562 * a higher level uio resid.
563 * maxreq - maximum (sequential heuristic) in bytes (highet typ ~2MB)
564 * bpp - return buffer (*bpp) for (loffset,blksize)
567 cluster_readcb(struct vnode *vp, off_t filesize, off_t loffset,
568 int blksize, size_t minreq, size_t maxreq,
569 void (*func)(struct bio *), void *arg)
571 struct buf *bp, *rbp, *reqbp;
582 * Calculate the desired read-ahead in blksize'd blocks (maxra).
583 * To do this we calculate maxreq.
585 * maxreq typically starts out as a sequential heuristic. If the
586 * high level uio/resid is bigger (minreq), we pop maxreq up to
587 * minreq. This represents the case where random I/O is being
588 * performed by the userland is issuing big read()'s.
590 * Then we limit maxreq to max_readahead to ensure it is a reasonable
593 * Finally we must ensure that (loffset + maxreq) does not cross the
594 * boundary (filesize) for the current blocksize. If we allowed it
595 * to cross we could end up with buffers past the boundary with the
596 * wrong block size (HAMMER large-data areas use mixed block sizes).
597 * minreq is also absolutely limited to filesize.
601 /* minreq not used beyond this point */
603 if (maxreq > max_readahead) {
604 maxreq = max_readahead;
605 if (maxreq > 16 * 1024 * 1024)
606 maxreq = 16 * 1024 * 1024;
608 if (maxreq < blksize)
610 if (loffset + maxreq > filesize) {
611 if (loffset > filesize)
614 maxreq = filesize - loffset;
617 maxra = (int)(maxreq / blksize);
620 * Get the requested block.
622 reqbp = bp = getblk(vp, loffset, blksize, 0, 0);
623 origoffset = loffset;
626 * Calculate the maximum cluster size for a single I/O, used
627 * by cluster_rbuild().
629 maxrbuild = vmaxiosize(vp) / blksize;
632 * if it is in the cache, then check to see if the reads have been
633 * sequential. If they have, then try some read-ahead, otherwise
634 * back-off on prospective read-aheads.
636 if (bp->b_flags & B_CACHE) {
638 * Setup for func() call whether we do read-ahead or not.
640 bp->b_bio1.bio_caller_info1.ptr = arg;
641 bp->b_bio1.bio_flags |= BIO_DONE;
644 * Not sequential, do not do any read-ahead
650 * No read-ahead mark, do not do any read-ahead
653 if ((bp->b_flags & B_RAM) == 0)
655 bp->b_flags &= ~B_RAM;
658 * We hit a read-ahead-mark, figure out how much read-ahead
659 * to do (maxra) and where to start (loffset).
661 * Shortcut the scan. Typically the way this works is that
662 * we've built up all the blocks inbetween except for the
663 * last in previous iterations, so if the second-to-last
664 * block is present we just skip ahead to it.
666 * This algorithm has O(1) cpu in the steady state no
667 * matter how large maxra is.
669 if (findblk(vp, loffset + (maxra - 2) * blksize, FINDBLK_TEST))
674 if (findblk(vp, loffset + i * blksize,
675 FINDBLK_TEST) == NULL) {
682 * We got everything or everything is in the cache, no
689 * Calculate where to start the read-ahead and how much
690 * to do. Generally speaking we want to read-ahead by
691 * (maxra) when we've found a read-ahead mark. We do
692 * not want to reduce maxra here as it will cause
693 * successive read-ahead I/O's to be smaller and smaller.
695 * However, we have to make sure we don't break the
696 * filesize limitation for the clustered operation.
698 loffset += i * blksize;
700 /* leave reqbp intact to force function callback */
702 if (loffset >= filesize)
704 if (loffset + maxra * blksize > filesize) {
705 maxreq = filesize - loffset;
706 maxra = (int)(maxreq / blksize);
711 * bp is not valid, no prior cluster in progress so get a
712 * full cluster read-ahead going.
714 __debugvar off_t firstread = bp->b_loffset;
719 * Set-up synchronous read for bp.
721 bp->b_flags &= ~(B_ERROR | B_EINTR | B_INVAL);
722 bp->b_cmd = BUF_CMD_READ;
723 bp->b_bio1.bio_done = func;
724 bp->b_bio1.bio_caller_info1.ptr = arg;
726 reqbp = NULL; /* don't func() reqbp, it's running async */
728 KASSERT(firstread != NOOFFSET,
729 ("cluster_read: no buffer offset"));
732 * nblks is our cluster_rbuild request size, limited
733 * primarily by the device.
735 nblks = calc_rbuild_reqsize(maxra, maxrbuild);
738 * Set RAM half-way through the full-cluster.
740 sr = (maxra + 1) / 2;
745 error = VOP_BMAP(vp, loffset, &doffset,
746 &burstbytes, NULL, BUF_CMD_READ);
748 goto single_block_read;
749 if (nblks > burstbytes / blksize)
750 nblks = burstbytes / blksize;
751 if (doffset == NOOFFSET)
752 goto single_block_read;
754 goto single_block_read;
756 bp = cluster_rbuild(vp, filesize, loffset,
757 doffset, blksize, nblks, bp, &sr);
758 loffset += bp->b_bufsize;
759 maxra -= bp->b_bufsize / blksize;
763 * If it isn't in the cache, then get a chunk from
764 * disk if sequential, otherwise just get the block.
772 * If bp != NULL then B_CACHE was *NOT* set and bp must be issued.
773 * bp will either be an asynchronous cluster buf or an asynchronous
776 * NOTE: Once an async cluster buf is issued bp becomes invalid.
779 #if defined(CLUSTERDEBUG)
781 kprintf("S(%012jx,%d,%d)\n",
782 (intmax_t)bp->b_loffset, bp->b_bcount, maxra);
784 if ((bp->b_flags & B_CLUSTER) == 0)
785 vfs_busy_pages(vp, bp);
786 bp->b_flags &= ~(B_ERROR|B_INVAL);
787 vn_strategy(vp, &bp->b_bio1);
792 #if defined(CLUSTERDEBUG)
794 kprintf("cluster_rd %016jx/%d maxra=%d sr=%d\n",
795 loffset, blksize, maxra, sr);
799 * If we have been doing sequential I/O, then do some read-ahead.
800 * The code above us should have positioned us at the next likely
803 * Only mess with buffers which we can immediately lock. HAMMER
804 * will do device-readahead irrespective of what the blocks
812 rbp = getblk(vp, loffset, blksize,
813 GETBLK_SZMATCH|GETBLK_NOWAIT, 0);
816 if ((rbp->b_flags & B_CACHE)) {
822 * If BMAP is not supported or has an issue, we still do
823 * (maxra) read-ahead, but we do not try to use rbuild.
825 error = VOP_BMAP(vp, loffset, &doffset,
826 &burstbytes, NULL, BUF_CMD_READ);
827 if (error || doffset == NOOFFSET) {
831 nblks = calc_rbuild_reqsize(maxra, maxrbuild);
832 if (nblks > burstbytes / blksize)
833 nblks = burstbytes / blksize;
835 rbp->b_cmd = BUF_CMD_READ;
838 rbp = cluster_rbuild(vp, filesize, loffset,
842 rbp->b_bio2.bio_offset = doffset;
847 rbp->b_flags &= ~(B_ERROR|B_INVAL);
849 if ((rbp->b_flags & B_CLUSTER) == 0)
850 vfs_busy_pages(vp, rbp);
852 loffset += rbp->b_bufsize;
853 maxra -= rbp->b_bufsize / blksize;
854 vn_strategy(vp, &rbp->b_bio1);
855 /* rbp invalid now */
859 * If reqbp is non-NULL it had B_CACHE set and we issue the
860 * function callback synchronously.
862 * Note that we may start additional asynchronous I/O before doing
863 * the func() callback for the B_CACHE case
867 func(&reqbp->b_bio1);
871 * If blocks are contiguous on disk, use this to provide clustered
872 * read ahead. We will read as many blocks as possible sequentially
873 * and then parcel them up into logical blocks in the buffer hash table.
875 * This function either returns a cluster buf or it returns fbp. fbp is
876 * already expected to be set up as a synchronous or asynchronous request.
878 * If a cluster buf is returned it will always be async.
880 * (*srp) counts down original blocks to determine where B_RAM should be set.
881 * Set B_RAM when *srp drops to 0. If (*srp) starts at 0, B_RAM will not be
882 * set on any buffer. Make sure B_RAM is cleared on any other buffers to
883 * prevent degenerate read-aheads from being generated.
886 cluster_rbuild(struct vnode *vp, off_t filesize, off_t loffset, off_t doffset,
887 int blksize, int run, struct buf *fbp, int *srp)
889 struct buf *bp, *tbp;
892 int maxiosize = vmaxiosize(vp);
897 while (loffset + run * blksize > filesize) {
902 tbp->b_bio2.bio_offset = doffset;
903 if((tbp->b_flags & B_MALLOC) ||
904 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1)) {
912 bp = trypbuf_kva(&cluster_pbuf_freecnt);
918 * We are synthesizing a buffer out of vm_page_t's, but
919 * if the block size is not page aligned then the starting
920 * address may not be either. Inherit the b_data offset
921 * from the original buffer.
923 bp->b_data = (char *)((vm_offset_t)bp->b_data |
924 ((vm_offset_t)tbp->b_data & PAGE_MASK));
925 bp->b_flags |= B_CLUSTER | B_VMIO;
926 bp->b_cmd = BUF_CMD_READ;
927 bp->b_bio1.bio_done = cluster_callback; /* default to async */
928 bp->b_bio1.bio_caller_info1.cluster_head = NULL;
929 bp->b_bio1.bio_caller_info2.cluster_tail = NULL;
930 bp->b_loffset = loffset;
931 bp->b_bio2.bio_offset = doffset;
932 KASSERT(bp->b_loffset != NOOFFSET,
933 ("cluster_rbuild: no buffer offset"));
937 bp->b_xio.xio_npages = 0;
939 for (boffset = doffset, i = 0; i < run; ++i, boffset += blksize) {
941 if ((bp->b_xio.xio_npages * PAGE_SIZE) +
942 round_page(blksize) > maxiosize) {
947 * Shortcut some checks and try to avoid buffers that
948 * would block in the lock. The same checks have to
949 * be made again after we officially get the buffer.
951 tbp = getblk(vp, loffset + i * blksize, blksize,
952 GETBLK_SZMATCH|GETBLK_NOWAIT, 0);
955 for (j = 0; j < tbp->b_xio.xio_npages; j++) {
956 if (tbp->b_xio.xio_pages[j]->valid)
959 if (j != tbp->b_xio.xio_npages) {
965 * Stop scanning if the buffer is fuly valid
966 * (marked B_CACHE), or locked (may be doing a
967 * background write), or if the buffer is not
968 * VMIO backed. The clustering code can only deal
969 * with VMIO-backed buffers.
971 if ((tbp->b_flags & (B_CACHE|B_LOCKED)) ||
972 (tbp->b_flags & B_VMIO) == 0 ||
973 (LIST_FIRST(&tbp->b_dep) != NULL &&
981 * The buffer must be completely invalid in order to
982 * take part in the cluster. If it is partially valid
985 for (j = 0;j < tbp->b_xio.xio_npages; j++) {
986 if (tbp->b_xio.xio_pages[j]->valid)
989 if (j != tbp->b_xio.xio_npages) {
995 * Depress the priority of buffers not explicitly
998 /* tbp->b_flags |= B_AGE; */
1001 * Set the block number if it isn't set, otherwise
1002 * if it is make sure it matches the block number we
1005 if (tbp->b_bio2.bio_offset == NOOFFSET) {
1006 tbp->b_bio2.bio_offset = boffset;
1007 } else if (tbp->b_bio2.bio_offset != boffset) {
1014 * Set B_RAM if (*srp) is 1. B_RAM is only set on one buffer
1015 * in the cluster, including potentially the first buffer
1016 * once we start streaming the read-aheads.
1019 cluster_setram(tbp);
1021 cluster_clrram(tbp);
1024 * The passed-in tbp (i == 0) will already be set up for
1025 * async or sync operation. All other tbp's acquire in
1026 * our loop are set up for async operation.
1028 tbp->b_cmd = BUF_CMD_READ;
1030 cluster_append(&bp->b_bio1, tbp);
1031 for (j = 0; j < tbp->b_xio.xio_npages; ++j) {
1034 m = tbp->b_xio.xio_pages[j];
1035 vm_page_busy_wait(m, FALSE, "clurpg");
1036 vm_page_io_start(m);
1038 vm_object_pip_add(m->object, 1);
1039 if ((bp->b_xio.xio_npages == 0) ||
1040 (bp->b_xio.xio_pages[bp->b_xio.xio_npages-1] != m)) {
1041 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m;
1042 bp->b_xio.xio_npages++;
1044 if ((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL)
1045 tbp->b_xio.xio_pages[j] = bogus_page;
1048 * XXX shouldn't this be += size for both, like in
1051 * Don't inherit tbp->b_bufsize as it may be larger due to
1052 * a non-page-aligned size. Instead just aggregate using
1055 if (tbp->b_bcount != blksize)
1056 kprintf("warning: tbp->b_bcount wrong %d vs %d\n", tbp->b_bcount, blksize);
1057 if (tbp->b_bufsize != blksize)
1058 kprintf("warning: tbp->b_bufsize wrong %d vs %d\n", tbp->b_bufsize, blksize);
1059 bp->b_bcount += blksize;
1060 bp->b_bufsize += blksize;
1064 * Fully valid pages in the cluster are already good and do not need
1065 * to be re-read from disk. Replace the page with bogus_page
1067 for (j = 0; j < bp->b_xio.xio_npages; j++) {
1068 if ((bp->b_xio.xio_pages[j]->valid & VM_PAGE_BITS_ALL) ==
1070 bp->b_xio.xio_pages[j] = bogus_page;
1073 if (bp->b_bufsize > bp->b_kvasize) {
1074 panic("cluster_rbuild: b_bufsize(%d) > b_kvasize(%d)",
1075 bp->b_bufsize, bp->b_kvasize);
1077 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
1078 (vm_page_t *)bp->b_xio.xio_pages, bp->b_xio.xio_npages);
1084 * Cleanup after a clustered read or write.
1085 * This is complicated by the fact that any of the buffers might have
1086 * extra memory (if there were no empty buffer headers at allocbuf time)
1087 * that we will need to shift around.
1089 * The returned bio is &bp->b_bio1
1092 cluster_callback(struct bio *bio)
1094 struct buf *bp = bio->bio_buf;
1099 * Must propogate errors to all the components. A short read (EOF)
1100 * is a critical error.
1102 if (bp->b_flags & B_ERROR) {
1103 error = bp->b_error;
1104 } else if (bp->b_bcount != bp->b_bufsize) {
1105 panic("cluster_callback: unexpected EOF on cluster %p!", bio);
1108 pmap_qremove(trunc_page((vm_offset_t) bp->b_data),
1109 bp->b_xio.xio_npages);
1111 * Move memory from the large cluster buffer into the component
1112 * buffers and mark IO as done on these. Since the memory map
1113 * is the same, no actual copying is required.
1115 while ((tbp = bio->bio_caller_info1.cluster_head) != NULL) {
1116 bio->bio_caller_info1.cluster_head = tbp->b_cluster_next;
1118 tbp->b_flags |= B_ERROR | B_IODEBUG;
1119 tbp->b_error = error;
1121 tbp->b_dirtyoff = tbp->b_dirtyend = 0;
1122 tbp->b_flags &= ~(B_ERROR|B_INVAL);
1123 tbp->b_flags |= B_IODEBUG;
1125 * XXX the bdwrite()/bqrelse() issued during
1126 * cluster building clears B_RELBUF (see bqrelse()
1127 * comment). If direct I/O was specified, we have
1128 * to restore it here to allow the buffer and VM
1131 if (tbp->b_flags & B_DIRECT)
1132 tbp->b_flags |= B_RELBUF;
1135 * XXX I think biodone() below will do this, but do
1136 * it here anyway for consistency.
1138 if (tbp->b_cmd == BUF_CMD_WRITE)
1141 biodone(&tbp->b_bio1);
1143 relpbuf(bp, &cluster_pbuf_freecnt);
1147 * Implement modified write build for cluster.
1149 * write_behind = 0 write behind disabled
1150 * write_behind = 1 write behind normal (default)
1151 * write_behind = 2 write behind backed-off
1153 * In addition, write_behind is only activated for files that have
1154 * grown past a certain size (default 10MB). Otherwise temporary files
1155 * wind up generating a lot of unnecessary disk I/O.
1158 cluster_wbuild_wb(struct vnode *vp, int blksize, off_t start_loffset, int len)
1162 switch(write_behind) {
1164 if (start_loffset < len)
1166 start_loffset -= len;
1169 if (vp->v_filesize >= write_behind_minfilesize) {
1170 r = cluster_wbuild(vp, NULL, blksize,
1171 start_loffset, len);
1182 * Do clustered write for FFS.
1185 * 1. Write is not sequential (write asynchronously)
1186 * Write is sequential:
1187 * 2. beginning of cluster - begin cluster
1188 * 3. middle of a cluster - add to cluster
1189 * 4. end of a cluster - asynchronously write cluster
1191 * WARNING! vnode fields are not locked and must ONLY be used heuristically.
1194 cluster_write(struct buf *bp, off_t filesize, int blksize, int seqcount)
1198 int maxclen, cursize;
1200 cluster_cache_t dummy;
1201 cluster_cache_t *cc;
1204 if (vp->v_type == VREG)
1205 async = vp->v_mount->mnt_flag & MNT_ASYNC;
1208 loffset = bp->b_loffset;
1209 KASSERT(bp->b_loffset != NOOFFSET,
1210 ("cluster_write: no buffer offset"));
1212 cc = cluster_getcache(&dummy, vp, loffset);
1215 * Initialize vnode to beginning of file.
1218 cc->v_lasta = cc->v_clen = cc->v_cstart = cc->v_lastw = 0;
1220 if (cc->v_clen == 0 || loffset != cc->v_lastw + blksize ||
1221 bp->b_bio2.bio_offset == NOOFFSET ||
1222 (bp->b_bio2.bio_offset != cc->v_lasta + blksize)) {
1223 maxclen = vmaxiosize(vp);
1224 if (cc->v_clen != 0) {
1226 * Next block is not sequential.
1228 * If we are not writing at end of file, the process
1229 * seeked to another point in the file since its last
1230 * write, or we have reached our maximum cluster size,
1231 * then push the previous cluster. Otherwise try
1232 * reallocating to make it sequential.
1234 * Change to algorithm: only push previous cluster if
1235 * it was sequential from the point of view of the
1236 * seqcount heuristic, otherwise leave the buffer
1237 * intact so we can potentially optimize the I/O
1238 * later on in the buf_daemon or update daemon
1241 cursize = cc->v_lastw - cc->v_cstart + blksize;
1242 if (bp->b_loffset + blksize < filesize ||
1243 loffset != cc->v_lastw + blksize ||
1244 cc->v_clen <= cursize) {
1245 if (!async && seqcount > 0) {
1246 cluster_wbuild_wb(vp, blksize,
1247 cc->v_cstart, cursize);
1250 struct buf **bpp, **endbp;
1251 struct cluster_save *buflist;
1253 buflist = cluster_collectbufs(cc, vp,
1255 endbp = &buflist->bs_children
1256 [buflist->bs_nchildren - 1];
1257 if (VOP_REALLOCBLKS(vp, buflist)) {
1259 * Failed, push the previous cluster
1260 * if *really* writing sequentially
1261 * in the logical file (seqcount > 1),
1262 * otherwise delay it in the hopes that
1263 * the low level disk driver can
1264 * optimize the write ordering.
1266 * NOTE: We do not brelse the last
1267 * element which is bp, and we
1268 * do not return here.
1270 for (bpp = buflist->bs_children;
1273 kfree(buflist, M_SEGMENT);
1275 cluster_wbuild_wb(vp,
1276 blksize, cc->v_cstart,
1281 * Succeeded, keep building cluster.
1283 for (bpp = buflist->bs_children;
1284 bpp <= endbp; bpp++)
1286 kfree(buflist, M_SEGMENT);
1287 cc->v_lastw = loffset;
1288 cc->v_lasta = bp->b_bio2.bio_offset;
1289 cluster_putcache(cc);
1295 * Consider beginning a cluster. If at end of file, make
1296 * cluster as large as possible, otherwise find size of
1299 if ((vp->v_type == VREG) &&
1300 bp->b_loffset + blksize < filesize &&
1301 (bp->b_bio2.bio_offset == NOOFFSET) &&
1302 (VOP_BMAP(vp, loffset, &bp->b_bio2.bio_offset, &maxclen, NULL, BUF_CMD_WRITE) ||
1303 bp->b_bio2.bio_offset == NOOFFSET)) {
1306 cc->v_lasta = bp->b_bio2.bio_offset;
1307 cc->v_cstart = loffset + blksize;
1308 cc->v_lastw = loffset;
1309 cluster_putcache(cc);
1312 if (maxclen > blksize)
1313 cc->v_clen = maxclen - blksize;
1316 if (!async && cc->v_clen == 0) { /* I/O not contiguous */
1317 cc->v_cstart = loffset + blksize;
1319 } else { /* Wait for rest of cluster */
1320 cc->v_cstart = loffset;
1323 } else if (loffset == cc->v_cstart + cc->v_clen) {
1325 * At end of cluster, write it out if seqcount tells us we
1326 * are operating sequentially, otherwise let the buf or
1327 * update daemon handle it.
1331 cluster_wbuild_wb(vp, blksize, cc->v_cstart,
1332 cc->v_clen + blksize);
1334 cc->v_cstart = loffset + blksize;
1335 } else if (vm_page_count_severe() &&
1336 bp->b_loffset + blksize < filesize) {
1338 * We are low on memory, get it going NOW. However, do not
1339 * try to push out a partial block at the end of the file
1340 * as this could lead to extremely non-optimal write activity.
1345 * In the middle of a cluster, so just delay the I/O for now.
1349 cc->v_lastw = loffset;
1350 cc->v_lasta = bp->b_bio2.bio_offset;
1351 cluster_putcache(cc);
1355 * This is the clustered version of bawrite(). It works similarly to
1356 * cluster_write() except I/O on the buffer is guaranteed to occur.
1359 cluster_awrite(struct buf *bp)
1364 * Don't bother if it isn't clusterable.
1366 if ((bp->b_flags & B_CLUSTEROK) == 0 ||
1368 (bp->b_vp->v_flag & VOBJBUF) == 0) {
1369 total = bp->b_bufsize;
1374 total = cluster_wbuild(bp->b_vp, &bp, bp->b_bufsize,
1375 bp->b_loffset, vmaxiosize(bp->b_vp));
1383 * This is an awful lot like cluster_rbuild...wish they could be combined.
1384 * The last lbn argument is the current block on which I/O is being
1385 * performed. Check to see that it doesn't fall in the middle of
1386 * the current block (if last_bp == NULL).
1388 * cluster_wbuild() normally does not guarantee anything. If bpp is
1389 * non-NULL and cluster_wbuild() is able to incorporate it into the
1390 * I/O it will set *bpp to NULL, otherwise it will leave it alone and
1391 * the caller must dispose of *bpp.
1394 cluster_wbuild(struct vnode *vp, struct buf **bpp,
1395 int blksize, off_t start_loffset, int bytes)
1397 struct buf *bp, *tbp;
1399 int totalwritten = 0;
1401 int maxiosize = vmaxiosize(vp);
1405 * If the buffer matches the passed locked & removed buffer
1406 * we used the passed buffer (which might not be B_DELWRI).
1408 * Otherwise locate the buffer and determine if it is
1411 if (bpp && (*bpp)->b_loffset == start_loffset) {
1416 tbp = findblk(vp, start_loffset, FINDBLK_NBLOCK);
1418 (tbp->b_flags & (B_LOCKED | B_INVAL | B_DELWRI)) !=
1420 (LIST_FIRST(&tbp->b_dep) && buf_checkwrite(tbp))) {
1423 start_loffset += blksize;
1429 KKASSERT(tbp->b_cmd == BUF_CMD_DONE);
1432 * Extra memory in the buffer, punt on this buffer.
1433 * XXX we could handle this in most cases, but we would
1434 * have to push the extra memory down to after our max
1435 * possible cluster size and then potentially pull it back
1436 * up if the cluster was terminated prematurely--too much
1439 if (((tbp->b_flags & (B_CLUSTEROK|B_MALLOC)) != B_CLUSTEROK) ||
1440 (tbp->b_bcount != tbp->b_bufsize) ||
1441 (tbp->b_bcount != blksize) ||
1442 (bytes == blksize) ||
1443 ((bp = getpbuf_kva(&cluster_pbuf_freecnt)) == NULL)) {
1444 totalwritten += tbp->b_bufsize;
1446 start_loffset += blksize;
1452 * Set up the pbuf. Track our append point with b_bcount
1453 * and b_bufsize. b_bufsize is not used by the device but
1454 * our caller uses it to loop clusters and we use it to
1455 * detect a premature EOF on the block device.
1459 bp->b_xio.xio_npages = 0;
1460 bp->b_loffset = tbp->b_loffset;
1461 bp->b_bio2.bio_offset = tbp->b_bio2.bio_offset;
1464 * We are synthesizing a buffer out of vm_page_t's, but
1465 * if the block size is not page aligned then the starting
1466 * address may not be either. Inherit the b_data offset
1467 * from the original buffer.
1469 bp->b_data = (char *)((vm_offset_t)bp->b_data |
1470 ((vm_offset_t)tbp->b_data & PAGE_MASK));
1471 bp->b_flags &= ~B_ERROR;
1472 bp->b_flags |= B_CLUSTER | B_BNOCLIP |
1473 (tbp->b_flags & (B_VMIO | B_NEEDCOMMIT));
1474 bp->b_bio1.bio_caller_info1.cluster_head = NULL;
1475 bp->b_bio1.bio_caller_info2.cluster_tail = NULL;
1478 * From this location in the file, scan forward to see
1479 * if there are buffers with adjacent data that need to
1480 * be written as well.
1482 * IO *must* be initiated on index 0 at this point
1483 * (particularly when called from cluster_awrite()).
1485 for (i = 0; i < bytes; (i += blksize), (start_loffset += blksize)) {
1493 tbp = findblk(vp, start_loffset,
1496 * Buffer not found or could not be locked
1503 * If it IS in core, but has different
1504 * characteristics, then don't cluster
1507 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
1508 B_INVAL | B_DELWRI | B_NEEDCOMMIT))
1509 != (B_DELWRI | B_CLUSTEROK |
1510 (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
1511 (tbp->b_flags & B_LOCKED)
1518 * Check that the combined cluster
1519 * would make sense with regard to pages
1520 * and would not be too large
1522 * WARNING! buf_checkwrite() must be the last
1523 * check made. If it returns 0 then
1524 * we must initiate the I/O.
1526 if ((tbp->b_bcount != blksize) ||
1527 ((bp->b_bio2.bio_offset + i) !=
1528 tbp->b_bio2.bio_offset) ||
1529 ((tbp->b_xio.xio_npages + bp->b_xio.xio_npages) >
1530 (maxiosize / PAGE_SIZE)) ||
1531 (LIST_FIRST(&tbp->b_dep) &&
1532 buf_checkwrite(tbp))
1537 if (LIST_FIRST(&tbp->b_dep))
1540 * Ok, it's passed all the tests,
1541 * so remove it from the free list
1542 * and mark it busy. We will use it.
1545 KKASSERT(tbp->b_cmd == BUF_CMD_DONE);
1549 * If the IO is via the VM then we do some
1550 * special VM hackery (yuck). Since the buffer's
1551 * block size may not be page-aligned it is possible
1552 * for a page to be shared between two buffers. We
1553 * have to get rid of the duplication when building
1556 if (tbp->b_flags & B_VMIO) {
1560 * Try to avoid deadlocks with the VM system.
1561 * However, we cannot abort the I/O if
1562 * must_initiate is non-zero.
1564 if (must_initiate == 0) {
1566 j < tbp->b_xio.xio_npages;
1568 m = tbp->b_xio.xio_pages[j];
1569 if (m->flags & PG_BUSY) {
1576 for (j = 0; j < tbp->b_xio.xio_npages; ++j) {
1577 m = tbp->b_xio.xio_pages[j];
1578 vm_page_busy_wait(m, FALSE, "clurpg");
1579 vm_page_io_start(m);
1581 vm_object_pip_add(m->object, 1);
1582 if ((bp->b_xio.xio_npages == 0) ||
1583 (bp->b_xio.xio_pages[bp->b_xio.xio_npages - 1] != m)) {
1584 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m;
1585 bp->b_xio.xio_npages++;
1589 bp->b_bcount += blksize;
1590 bp->b_bufsize += blksize;
1593 * NOTE: see bwrite/bawrite code for why we no longer
1596 * bundirty(tbp); REMOVED
1598 tbp->b_flags &= ~B_ERROR;
1599 tbp->b_cmd = BUF_CMD_WRITE;
1601 cluster_append(&bp->b_bio1, tbp);
1604 * check for latent dependencies to be handled
1606 if (LIST_FIRST(&tbp->b_dep) != NULL)
1610 pmap_qenter(trunc_page((vm_offset_t)bp->b_data),
1611 (vm_page_t *)bp->b_xio.xio_pages,
1612 bp->b_xio.xio_npages);
1613 if (bp->b_bufsize > bp->b_kvasize) {
1614 panic("cluster_wbuild: b_bufsize(%d) "
1615 "> b_kvasize(%d)\n",
1616 bp->b_bufsize, bp->b_kvasize);
1618 totalwritten += bp->b_bufsize;
1620 bp->b_dirtyend = bp->b_bufsize;
1621 bp->b_bio1.bio_done = cluster_callback;
1622 bp->b_cmd = BUF_CMD_WRITE;
1624 vfs_busy_pages(vp, bp);
1625 bsetrunningbufspace(bp, bp->b_bufsize);
1627 vn_strategy(vp, &bp->b_bio1);
1631 return totalwritten;
1635 * Collect together all the buffers in a cluster, plus add one
1636 * additional buffer passed-in.
1638 * Only pre-existing buffers whos block size matches blksize are collected.
1639 * (this is primarily because HAMMER1 uses varying block sizes and we don't
1640 * want to override its choices).
1642 * This code will not try to collect buffers that it cannot lock, otherwise
1643 * it might deadlock against SMP-friendly filesystems.
1645 static struct cluster_save *
1646 cluster_collectbufs(cluster_cache_t *cc, struct vnode *vp,
1647 struct buf *last_bp, int blksize)
1649 struct cluster_save *buflist;
1656 len = (int)(cc->v_lastw - cc->v_cstart + blksize) / blksize;
1658 buflist = kmalloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
1659 M_SEGMENT, M_WAITOK);
1660 buflist->bs_nchildren = 0;
1661 buflist->bs_children = (struct buf **) (buflist + 1);
1662 for (loffset = cc->v_cstart, i = 0, j = 0;
1664 (loffset += blksize), i++) {
1665 bp = getcacheblk(vp, loffset,
1666 last_bp->b_bcount, GETBLK_SZMATCH |
1668 buflist->bs_children[i] = bp;
1671 } else if (bp->b_bio2.bio_offset == NOOFFSET) {
1672 VOP_BMAP(bp->b_vp, bp->b_loffset,
1673 &bp->b_bio2.bio_offset,
1674 NULL, NULL, BUF_CMD_WRITE);
1681 for (k = 0; k < j; ++k) {
1682 if (buflist->bs_children[k]) {
1683 bqrelse(buflist->bs_children[k]);
1684 buflist->bs_children[k] = NULL;
1689 bcopy(buflist->bs_children + j,
1690 buflist->bs_children + 0,
1691 sizeof(buflist->bs_children[0]) * (i - j));
1695 buflist->bs_children[i] = bp = last_bp;
1696 if (bp->b_bio2.bio_offset == NOOFFSET) {
1697 VOP_BMAP(bp->b_vp, bp->b_loffset, &bp->b_bio2.bio_offset,
1698 NULL, NULL, BUF_CMD_WRITE);
1700 buflist->bs_nchildren = i + 1;
1705 cluster_append(struct bio *bio, struct buf *tbp)
1707 tbp->b_cluster_next = NULL;
1708 if (bio->bio_caller_info1.cluster_head == NULL) {
1709 bio->bio_caller_info1.cluster_head = tbp;
1710 bio->bio_caller_info2.cluster_tail = tbp;
1712 bio->bio_caller_info2.cluster_tail->b_cluster_next = tbp;
1713 bio->bio_caller_info2.cluster_tail = tbp;
1719 cluster_setram(struct buf *bp)
1721 bp->b_flags |= B_RAM;
1722 if (bp->b_xio.xio_npages)
1723 vm_page_flag_set(bp->b_xio.xio_pages[0], PG_RAM);
1728 cluster_clrram(struct buf *bp)
1730 bp->b_flags &= ~B_RAM;
1731 if (bp->b_xio.xio_npages)
1732 vm_page_flag_clear(bp->b_xio.xio_pages[0], PG_RAM);