kernel - SWAP CACHE part 1/many - Convert swblock to a Red-Black tree
[dragonfly.git] / sys / vm / swap_pager.c
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1 /*
2 * Copyright (c) 1998,2004 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
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
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
34 * Copyright (c) 1994 John S. Dyson
35 * Copyright (c) 1990 University of Utah.
36 * Copyright (c) 1991, 1993
37 * The Regents of the University of California. All rights reserved.
39 * This code is derived from software contributed to Berkeley by
40 * the Systems Programming Group of the University of Utah Computer
41 * Science Department.
43 * Redistribution and use in source and binary forms, with or without
44 * modification, are permitted provided that the following conditions
45 * are met:
46 * 1. Redistributions of source code must retain the above copyright
47 * notice, this list of conditions and the following disclaimer.
48 * 2. Redistributions in binary form must reproduce the above copyright
49 * notice, this list of conditions and the following disclaimer in the
50 * documentation and/or other materials provided with the distribution.
51 * 3. All advertising materials mentioning features or use of this software
52 * must display the following acknowledgement:
53 * This product includes software developed by the University of
54 * California, Berkeley and its contributors.
55 * 4. Neither the name of the University nor the names of its contributors
56 * may be used to endorse or promote products derived from this software
57 * without specific prior written permission.
59 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
62 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
69 * SUCH DAMAGE.
71 * New Swap System
72 * Matthew Dillon
74 * Radix Bitmap 'blists'.
76 * - The new swapper uses the new radix bitmap code. This should scale
77 * to arbitrarily small or arbitrarily large swap spaces and an almost
78 * arbitrary degree of fragmentation.
80 * Features:
82 * - on the fly reallocation of swap during putpages. The new system
83 * does not try to keep previously allocated swap blocks for dirty
84 * pages.
86 * - on the fly deallocation of swap
88 * - No more garbage collection required. Unnecessarily allocated swap
89 * blocks only exist for dirty vm_page_t's now and these are already
90 * cycled (in a high-load system) by the pager. We also do on-the-fly
91 * removal of invalidated swap blocks when a page is destroyed
92 * or renamed.
94 * from: Utah $Hdr: swap_pager.c 1.4 91/04/30$
96 * @(#)swap_pager.c 8.9 (Berkeley) 3/21/94
98 * $FreeBSD: src/sys/vm/swap_pager.c,v 1.130.2.12 2002/08/31 21:15:55 dillon Exp $
99 * $DragonFly: src/sys/vm/swap_pager.c,v 1.32 2008/07/01 02:02:56 dillon Exp $
102 #include <sys/param.h>
103 #include <sys/systm.h>
104 #include <sys/conf.h>
105 #include <sys/kernel.h>
106 #include <sys/proc.h>
107 #include <sys/buf.h>
108 #include <sys/vnode.h>
109 #include <sys/malloc.h>
110 #include <sys/vmmeter.h>
111 #include <sys/sysctl.h>
112 #include <sys/blist.h>
113 #include <sys/lock.h>
114 #include <sys/thread2.h>
116 #ifndef MAX_PAGEOUT_CLUSTER
117 #define MAX_PAGEOUT_CLUSTER 16
118 #endif
120 #define SWB_NPAGES MAX_PAGEOUT_CLUSTER
122 #include "opt_swap.h"
123 #include <vm/vm.h>
124 #include <vm/vm_object.h>
125 #include <vm/vm_page.h>
126 #include <vm/vm_pager.h>
127 #include <vm/vm_pageout.h>
128 #include <vm/swap_pager.h>
129 #include <vm/vm_extern.h>
130 #include <vm/vm_zone.h>
131 #include <vm/vnode_pager.h>
133 #include <sys/buf2.h>
134 #include <vm/vm_page2.h>
136 #define SWM_FREE 0x02 /* free, period */
137 #define SWM_POP 0x04 /* pop out */
139 #define SWBIO_READ 0x01
140 #define SWBIO_WRITE 0x02
141 #define SWBIO_SYNC 0x04
144 * vm_swap_size is in page-sized chunks now. It was DEV_BSIZE'd chunks
145 * in the old system.
148 extern int vm_swap_size; /* number of free swap blocks, in pages */
150 int swap_pager_full; /* swap space exhaustion (task killing) */
151 static int swap_pager_almost_full; /* swap space exhaustion (w/ hysteresis)*/
152 static int nsw_rcount; /* free read buffers */
153 static int nsw_wcount_sync; /* limit write buffers / synchronous */
154 static int nsw_wcount_async; /* limit write buffers / asynchronous */
155 static int nsw_wcount_async_max;/* assigned maximum */
156 static int nsw_cluster_max; /* maximum VOP I/O allowed */
157 static int sw_alloc_interlock; /* swap pager allocation interlock */
159 struct blist *swapblist;
160 static int swap_async_max = 4; /* maximum in-progress async I/O's */
161 static int swap_burst_read = 0; /* allow burst reading */
163 extern struct vnode *swapdev_vp; /* from vm_swap.c */
165 SYSCTL_INT(_vm, OID_AUTO, swap_async_max,
166 CTLFLAG_RW, &swap_async_max, 0, "Maximum running async swap ops");
167 SYSCTL_INT(_vm, OID_AUTO, swap_burst_read,
168 CTLFLAG_RW, &swap_burst_read, 0, "Allow burst reads for pageins");
171 * "named" and "unnamed" anon region objects. Try to reduce the overhead
172 * of searching a named list by hashing it just a little.
175 #define NOBJLISTS 8
177 #define NOBJLIST(handle) \
178 (&swap_pager_object_list[((int)(intptr_t)handle >> 4) & (NOBJLISTS-1)])
180 static struct pagerlst swap_pager_object_list[NOBJLISTS];
181 struct pagerlst swap_pager_un_object_list;
182 vm_zone_t swap_zone;
185 * Red-Black tree for swblock entries
187 RB_GENERATE2(swblock_rb_tree, swblock, swb_entry, rb_swblock_compare,
188 vm_pindex_t, swb_index);
191 rb_swblock_compare(struct swblock *swb1, struct swblock *swb2)
193 if (swb1->swb_index < swb2->swb_index)
194 return(-1);
195 if (swb1->swb_index > swb2->swb_index)
196 return(1);
197 return(0);
201 * pagerops for OBJT_SWAP - "swap pager". Some ops are also global procedure
202 * calls hooked from other parts of the VM system and do not appear here.
203 * (see vm/swap_pager.h).
206 static vm_object_t
207 swap_pager_alloc (void *handle, off_t size,
208 vm_prot_t prot, off_t offset);
209 static void swap_pager_dealloc (vm_object_t object);
210 static int swap_pager_getpage (vm_object_t, vm_page_t *, int);
211 static void swap_pager_init (void);
212 static void swap_pager_unswapped (vm_page_t);
213 static void swap_pager_strategy (vm_object_t, struct bio *);
214 static void swap_chain_iodone(struct bio *biox);
216 struct pagerops swappagerops = {
217 swap_pager_init, /* early system initialization of pager */
218 swap_pager_alloc, /* allocate an OBJT_SWAP object */
219 swap_pager_dealloc, /* deallocate an OBJT_SWAP object */
220 swap_pager_getpage, /* pagein */
221 swap_pager_putpages, /* pageout */
222 swap_pager_haspage, /* get backing store status for page */
223 swap_pager_unswapped, /* remove swap related to page */
224 swap_pager_strategy /* pager strategy call */
228 * dmmax is in page-sized chunks with the new swap system. It was
229 * dev-bsized chunks in the old. dmmax is always a power of 2.
231 * swap_*() routines are externally accessible. swp_*() routines are
232 * internal.
235 int dmmax;
236 static int dmmax_mask;
237 int nswap_lowat = 128; /* in pages, swap_pager_almost_full warn */
238 int nswap_hiwat = 512; /* in pages, swap_pager_almost_full warn */
240 static __inline void swp_sizecheck (void);
241 static void swp_pager_async_iodone (struct bio *bio);
244 * Swap bitmap functions
247 static __inline void swp_pager_freeswapspace (daddr_t blk, int npages);
248 static __inline daddr_t swp_pager_getswapspace (int npages);
251 * Metadata functions
254 static void swp_pager_meta_convert (vm_object_t);
255 static void swp_pager_meta_build (vm_object_t, vm_pindex_t, daddr_t);
256 static void swp_pager_meta_free (vm_object_t, vm_pindex_t, daddr_t);
257 static void swp_pager_meta_free_all (vm_object_t);
258 static daddr_t swp_pager_meta_ctl (vm_object_t, vm_pindex_t, int);
261 * SWP_SIZECHECK() - update swap_pager_full indication
263 * update the swap_pager_almost_full indication and warn when we are
264 * about to run out of swap space, using lowat/hiwat hysteresis.
266 * Clear swap_pager_full ( task killing ) indication when lowat is met.
268 * No restrictions on call
269 * This routine may not block.
270 * This routine must be called at splvm()
273 static __inline void
274 swp_sizecheck(void)
276 if (vm_swap_size < nswap_lowat) {
277 if (swap_pager_almost_full == 0) {
278 kprintf("swap_pager: out of swap space\n");
279 swap_pager_almost_full = 1;
281 } else {
282 swap_pager_full = 0;
283 if (vm_swap_size > nswap_hiwat)
284 swap_pager_almost_full = 0;
289 * SWAP_PAGER_INIT() - initialize the swap pager!
291 * Expected to be started from system init. NOTE: This code is run
292 * before much else so be careful what you depend on. Most of the VM
293 * system has yet to be initialized at this point.
296 static void
297 swap_pager_init(void)
300 * Initialize object lists
302 int i;
304 for (i = 0; i < NOBJLISTS; ++i)
305 TAILQ_INIT(&swap_pager_object_list[i]);
306 TAILQ_INIT(&swap_pager_un_object_list);
309 * Device Stripe, in PAGE_SIZE'd blocks
312 dmmax = SWB_NPAGES * 2;
313 dmmax_mask = ~(dmmax - 1);
317 * SWAP_PAGER_SWAP_INIT() - swap pager initialization from pageout process
319 * Expected to be started from pageout process once, prior to entering
320 * its main loop.
323 void
324 swap_pager_swap_init(void)
326 int n, n2;
329 * Number of in-transit swap bp operations. Don't
330 * exhaust the pbufs completely. Make sure we
331 * initialize workable values (0 will work for hysteresis
332 * but it isn't very efficient).
334 * The nsw_cluster_max is constrained by the number of pages an XIO
335 * holds, i.e., (MAXPHYS/PAGE_SIZE) and our locally defined
336 * MAX_PAGEOUT_CLUSTER. Also be aware that swap ops are
337 * constrained by the swap device interleave stripe size.
339 * Currently we hardwire nsw_wcount_async to 4. This limit is
340 * designed to prevent other I/O from having high latencies due to
341 * our pageout I/O. The value 4 works well for one or two active swap
342 * devices but is probably a little low if you have more. Even so,
343 * a higher value would probably generate only a limited improvement
344 * with three or four active swap devices since the system does not
345 * typically have to pageout at extreme bandwidths. We will want
346 * at least 2 per swap devices, and 4 is a pretty good value if you
347 * have one NFS swap device due to the command/ack latency over NFS.
348 * So it all works out pretty well.
351 nsw_cluster_max = min((MAXPHYS/PAGE_SIZE), MAX_PAGEOUT_CLUSTER);
353 nsw_rcount = (nswbuf + 1) / 2;
354 nsw_wcount_sync = (nswbuf + 3) / 4;
355 nsw_wcount_async = 4;
356 nsw_wcount_async_max = nsw_wcount_async;
359 * The zone is dynamically allocated so generally size it to
360 * maxswzone (32MB to 512MB of KVM). Set a minimum size based
361 * on physical memory of around 8x (each swblock can hold 16 pages).
363 * With the advent of SSDs (vs HDs) the practical (swap:memory) ratio
364 * has increased dramatically.
366 n = vmstats.v_page_count / 2;
367 if (maxswzone && n < maxswzone / sizeof(struct swblock))
368 n = maxswzone / sizeof(struct swblock);
369 n2 = n;
371 do {
372 swap_zone = zinit(
373 "SWAPMETA",
374 sizeof(struct swblock),
376 ZONE_INTERRUPT,
378 if (swap_zone != NULL)
379 break;
381 * if the allocation failed, try a zone two thirds the
382 * size of the previous attempt.
384 n -= ((n + 2) / 3);
385 } while (n > 0);
387 if (swap_zone == NULL)
388 panic("swap_pager_swap_init: swap_zone == NULL");
389 if (n2 != n)
390 kprintf("Swap zone entries reduced from %d to %d.\n", n2, n);
394 * SWAP_PAGER_ALLOC() - allocate a new OBJT_SWAP VM object and instantiate
395 * its metadata structures.
397 * This routine is called from the mmap and fork code to create a new
398 * OBJT_SWAP object. We do this by creating an OBJT_DEFAULT object
399 * and then converting it with swp_pager_meta_convert().
401 * This routine may block in vm_object_allocate() and create a named
402 * object lookup race, so we must interlock. We must also run at
403 * splvm() for the object lookup to handle races with interrupts, but
404 * we do not have to maintain splvm() in between the lookup and the
405 * add because (I believe) it is not possible to attempt to create
406 * a new swap object w/handle when a default object with that handle
407 * already exists.
410 static vm_object_t
411 swap_pager_alloc(void *handle, off_t size, vm_prot_t prot, off_t offset)
413 vm_object_t object;
415 if (handle) {
417 * Reference existing named region or allocate new one. There
418 * should not be a race here against swp_pager_meta_build()
419 * as called from vm_page_remove() in regards to the lookup
420 * of the handle.
422 while (sw_alloc_interlock) {
423 sw_alloc_interlock = -1;
424 tsleep(&sw_alloc_interlock, 0, "swpalc", 0);
426 sw_alloc_interlock = 1;
428 object = vm_pager_object_lookup(NOBJLIST(handle), handle);
430 if (object != NULL) {
431 vm_object_reference(object);
432 } else {
433 object = vm_object_allocate(OBJT_DEFAULT,
434 OFF_TO_IDX(offset + PAGE_MASK + size));
435 object->handle = handle;
436 swp_pager_meta_convert(object);
439 if (sw_alloc_interlock < 0)
440 wakeup(&sw_alloc_interlock);
441 sw_alloc_interlock = 0;
442 } else {
443 object = vm_object_allocate(OBJT_DEFAULT,
444 OFF_TO_IDX(offset + PAGE_MASK + size));
445 swp_pager_meta_convert(object);
448 return (object);
452 * SWAP_PAGER_DEALLOC() - remove swap metadata from object
454 * The swap backing for the object is destroyed. The code is
455 * designed such that we can reinstantiate it later, but this
456 * routine is typically called only when the entire object is
457 * about to be destroyed.
459 * This routine may block, but no longer does.
461 * The object must be locked or unreferenceable.
464 static void
465 swap_pager_dealloc(vm_object_t object)
468 * Remove from list right away so lookups will fail if we block for
469 * pageout completion.
472 if (object->handle == NULL) {
473 TAILQ_REMOVE(&swap_pager_un_object_list, object, pager_object_list);
474 } else {
475 TAILQ_REMOVE(NOBJLIST(object->handle), object, pager_object_list);
478 vm_object_pip_wait(object, "swpdea");
481 * Free all remaining metadata. We only bother to free it from
482 * the swap meta data. We do not attempt to free swapblk's still
483 * associated with vm_page_t's for this object. We do not care
484 * if paging is still in progress on some objects.
486 crit_enter();
487 swp_pager_meta_free_all(object);
488 crit_exit();
491 /************************************************************************
492 * SWAP PAGER BITMAP ROUTINES *
493 ************************************************************************/
496 * SWP_PAGER_GETSWAPSPACE() - allocate raw swap space
498 * Allocate swap for the requested number of pages. The starting
499 * swap block number (a page index) is returned or SWAPBLK_NONE
500 * if the allocation failed.
502 * Also has the side effect of advising that somebody made a mistake
503 * when they configured swap and didn't configure enough.
505 * Must be called at splvm() to avoid races with bitmap frees from
506 * vm_page_remove() aka swap_pager_page_removed().
508 * This routine may not block
509 * This routine must be called at splvm().
512 static __inline daddr_t
513 swp_pager_getswapspace(int npages)
515 daddr_t blk;
517 if ((blk = blist_alloc(swapblist, npages)) == SWAPBLK_NONE) {
518 if (swap_pager_full != 2) {
519 kprintf("swap_pager_getswapspace: failed\n");
520 swap_pager_full = 2;
521 swap_pager_almost_full = 1;
523 } else {
524 vm_swap_size -= npages;
525 swp_sizecheck();
527 return(blk);
531 * SWP_PAGER_FREESWAPSPACE() - free raw swap space
533 * This routine returns the specified swap blocks back to the bitmap.
535 * Note: This routine may not block (it could in the old swap code),
536 * and through the use of the new blist routines it does not block.
538 * We must be called at splvm() to avoid races with bitmap frees from
539 * vm_page_remove() aka swap_pager_page_removed().
541 * This routine may not block
542 * This routine must be called at splvm().
545 static __inline void
546 swp_pager_freeswapspace(daddr_t blk, int npages)
548 blist_free(swapblist, blk, npages);
549 vm_swap_size += npages;
550 swp_sizecheck();
554 * SWAP_PAGER_FREESPACE() - frees swap blocks associated with a page
555 * range within an object.
557 * This is a globally accessible routine.
559 * This routine removes swapblk assignments from swap metadata.
561 * The external callers of this routine typically have already destroyed
562 * or renamed vm_page_t's associated with this range in the object so
563 * we should be ok.
565 * This routine may be called at any spl. We up our spl to splvm
566 * temporarily in order to perform the metadata removal.
568 void
569 swap_pager_freespace(vm_object_t object, vm_pindex_t start, vm_size_t size)
571 crit_enter();
572 swp_pager_meta_free(object, start, size);
573 crit_exit();
577 * SWAP_PAGER_RESERVE() - reserve swap blocks in object
579 * Assigns swap blocks to the specified range within the object. The
580 * swap blocks are not zerod. Any previous swap assignment is destroyed.
582 * Returns 0 on success, -1 on failure.
585 swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_size_t size)
587 int n = 0;
588 daddr_t blk = SWAPBLK_NONE;
589 vm_pindex_t beg = start; /* save start index */
591 crit_enter();
592 while (size) {
593 if (n == 0) {
594 n = BLIST_MAX_ALLOC;
595 while ((blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE) {
596 n >>= 1;
597 if (n == 0) {
598 swp_pager_meta_free(object, beg, start - beg);
599 crit_exit();
600 return(-1);
604 swp_pager_meta_build(object, start, blk);
605 --size;
606 ++start;
607 ++blk;
608 --n;
610 swp_pager_meta_free(object, start, n);
611 crit_exit();
612 return(0);
616 * SWAP_PAGER_COPY() - copy blocks from source pager to destination pager
617 * and destroy the source.
619 * Copy any valid swapblks from the source to the destination. In
620 * cases where both the source and destination have a valid swapblk,
621 * we keep the destination's.
623 * This routine is allowed to block. It may block allocating metadata
624 * indirectly through swp_pager_meta_build() or if paging is still in
625 * progress on the source.
627 * This routine can be called at any spl
629 * XXX vm_page_collapse() kinda expects us not to block because we
630 * supposedly do not need to allocate memory, but for the moment we
631 * *may* have to get a little memory from the zone allocator, but
632 * it is taken from the interrupt memory. We should be ok.
634 * The source object contains no vm_page_t's (which is just as well)
636 * The source object is of type OBJT_SWAP.
638 * The source and destination objects must be locked or
639 * inaccessible (XXX are they ?)
642 void
643 swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject,
644 vm_pindex_t offset, int destroysource)
646 vm_pindex_t i;
648 crit_enter();
651 * If destroysource is set, we remove the source object from the
652 * swap_pager internal queue now.
655 if (destroysource) {
656 if (srcobject->handle == NULL) {
657 TAILQ_REMOVE(
658 &swap_pager_un_object_list,
659 srcobject,
660 pager_object_list
662 } else {
663 TAILQ_REMOVE(
664 NOBJLIST(srcobject->handle),
665 srcobject,
666 pager_object_list
672 * transfer source to destination.
675 for (i = 0; i < dstobject->size; ++i) {
676 daddr_t dstaddr;
679 * Locate (without changing) the swapblk on the destination,
680 * unless it is invalid in which case free it silently, or
681 * if the destination is a resident page, in which case the
682 * source is thrown away.
685 dstaddr = swp_pager_meta_ctl(dstobject, i, 0);
687 if (dstaddr == SWAPBLK_NONE) {
689 * Destination has no swapblk and is not resident,
690 * copy source.
692 daddr_t srcaddr;
694 srcaddr = swp_pager_meta_ctl(
695 srcobject,
696 i + offset,
697 SWM_POP
700 if (srcaddr != SWAPBLK_NONE)
701 swp_pager_meta_build(dstobject, i, srcaddr);
702 } else {
704 * Destination has valid swapblk or it is represented
705 * by a resident page. We destroy the sourceblock.
708 swp_pager_meta_ctl(srcobject, i + offset, SWM_FREE);
713 * Free left over swap blocks in source.
715 * We have to revert the type to OBJT_DEFAULT so we do not accidently
716 * double-remove the object from the swap queues.
719 if (destroysource) {
721 * Reverting the type is not necessary, the caller is going
722 * to destroy srcobject directly, but I'm doing it here
723 * for consistency since we've removed the object from its
724 * queues.
726 swp_pager_meta_free_all(srcobject);
727 srcobject->type = OBJT_DEFAULT;
729 crit_exit();
733 * SWAP_PAGER_HASPAGE() - determine if we have good backing store for
734 * the requested page.
736 * We determine whether good backing store exists for the requested
737 * page and return TRUE if it does, FALSE if it doesn't.
739 * If TRUE, we also try to determine how much valid, contiguous backing
740 * store exists before and after the requested page within a reasonable
741 * distance. We do not try to restrict it to the swap device stripe
742 * (that is handled in getpages/putpages). It probably isn't worth
743 * doing here.
746 boolean_t
747 swap_pager_haspage(vm_object_t object, vm_pindex_t pindex)
749 daddr_t blk0;
752 * do we have good backing store at the requested index ?
755 crit_enter();
756 blk0 = swp_pager_meta_ctl(object, pindex, 0);
758 if (blk0 == SWAPBLK_NONE) {
759 crit_exit();
760 return (FALSE);
763 #if 0
765 * find backwards-looking contiguous good backing store
767 if (before != NULL) {
768 int i;
770 for (i = 1; i < (SWB_NPAGES/2); ++i) {
771 daddr_t blk;
773 if (i > pindex)
774 break;
775 blk = swp_pager_meta_ctl(object, pindex - i, 0);
776 if (blk != blk0 - i)
777 break;
779 *before = (i - 1);
783 * find forward-looking contiguous good backing store
786 if (after != NULL) {
787 int i;
789 for (i = 1; i < (SWB_NPAGES/2); ++i) {
790 daddr_t blk;
792 blk = swp_pager_meta_ctl(object, pindex + i, 0);
793 if (blk != blk0 + i)
794 break;
796 *after = (i - 1);
798 #endif
799 crit_exit();
800 return (TRUE);
804 * SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page
806 * This removes any associated swap backing store, whether valid or
807 * not, from the page.
809 * This routine is typically called when a page is made dirty, at
810 * which point any associated swap can be freed. MADV_FREE also
811 * calls us in a special-case situation
813 * NOTE!!! If the page is clean and the swap was valid, the caller
814 * should make the page dirty before calling this routine. This routine
815 * does NOT change the m->dirty status of the page. Also: MADV_FREE
816 * depends on it.
818 * This routine may not block
819 * This routine must be called at splvm()
822 static void
823 swap_pager_unswapped(vm_page_t m)
825 swp_pager_meta_ctl(m->object, m->pindex, SWM_FREE);
829 * SWAP_PAGER_STRATEGY() - read, write, free blocks
831 * This implements the vm_pager_strategy() interface to swap and allows
832 * other parts of the system to directly access swap as backing store
833 * through vm_objects of type OBJT_SWAP. This is intended to be a
834 * cacheless interface ( i.e. caching occurs at higher levels ).
835 * Therefore we do not maintain any resident pages. All I/O goes
836 * directly to and from the swap device.
838 * We currently attempt to run I/O synchronously or asynchronously as
839 * the caller requests. This isn't perfect because we loose error
840 * sequencing when we run multiple ops in parallel to satisfy a request.
841 * But this is swap, so we let it all hang out.
844 static void
845 swap_pager_strategy(vm_object_t object, struct bio *bio)
847 struct buf *bp = bio->bio_buf;
848 struct bio *nbio;
849 vm_pindex_t start;
850 vm_pindex_t biox_blkno = 0;
851 int count;
852 char *data;
853 struct bio *biox;
854 struct buf *bufx;
855 struct bio_track *track;
858 * tracking for swapdev vnode I/Os
860 if (bp->b_cmd == BUF_CMD_READ)
861 track = &swapdev_vp->v_track_read;
862 else
863 track = &swapdev_vp->v_track_write;
865 if (bp->b_bcount & PAGE_MASK) {
866 bp->b_error = EINVAL;
867 bp->b_flags |= B_ERROR | B_INVAL;
868 biodone(bio);
869 kprintf("swap_pager_strategy: bp %p offset %lld size %d, "
870 "not page bounded\n",
871 bp, (long long)bio->bio_offset, (int)bp->b_bcount);
872 return;
876 * Clear error indication, initialize page index, count, data pointer.
878 bp->b_error = 0;
879 bp->b_flags &= ~B_ERROR;
880 bp->b_resid = bp->b_bcount;
882 start = (vm_pindex_t)(bio->bio_offset >> PAGE_SHIFT);
883 count = howmany(bp->b_bcount, PAGE_SIZE);
884 data = bp->b_data;
887 * Deal with BUF_CMD_FREEBLKS
889 if (bp->b_cmd == BUF_CMD_FREEBLKS) {
891 * FREE PAGE(s) - destroy underlying swap that is no longer
892 * needed.
894 swp_pager_meta_free(object, start, count);
895 bp->b_resid = 0;
896 biodone(bio);
897 return;
901 * We need to be able to create a new cluster of I/O's. We cannot
902 * use the caller fields of the passed bio so push a new one.
904 * Because nbio is just a placeholder for the cluster links,
905 * we can biodone() the original bio instead of nbio to make
906 * things a bit more efficient.
908 nbio = push_bio(bio);
909 nbio->bio_offset = bio->bio_offset;
910 nbio->bio_caller_info1.cluster_head = NULL;
911 nbio->bio_caller_info2.cluster_tail = NULL;
913 biox = NULL;
914 bufx = NULL;
917 * Execute read or write
919 while (count > 0) {
920 daddr_t blk;
923 * Obtain block. If block not found and writing, allocate a
924 * new block and build it into the object.
926 blk = swp_pager_meta_ctl(object, start, 0);
927 if ((blk == SWAPBLK_NONE) && bp->b_cmd != BUF_CMD_READ) {
928 blk = swp_pager_getswapspace(1);
929 if (blk == SWAPBLK_NONE) {
930 bp->b_error = ENOMEM;
931 bp->b_flags |= B_ERROR;
932 break;
934 swp_pager_meta_build(object, start, blk);
938 * Do we have to flush our current collection? Yes if:
940 * - no swap block at this index
941 * - swap block is not contiguous
942 * - we cross a physical disk boundry in the
943 * stripe.
945 if (
946 biox && (biox_blkno + btoc(bufx->b_bcount) != blk ||
947 ((biox_blkno ^ blk) & dmmax_mask)
950 if (bp->b_cmd == BUF_CMD_READ) {
951 ++mycpu->gd_cnt.v_swapin;
952 mycpu->gd_cnt.v_swappgsin += btoc(bufx->b_bcount);
953 } else {
954 ++mycpu->gd_cnt.v_swapout;
955 mycpu->gd_cnt.v_swappgsout += btoc(bufx->b_bcount);
956 bufx->b_dirtyend = bufx->b_bcount;
960 * Finished with this buf.
962 KKASSERT(bufx->b_bcount != 0);
963 if (bufx->b_cmd != BUF_CMD_READ)
964 bufx->b_dirtyend = bufx->b_bcount;
965 biox = NULL;
966 bufx = NULL;
970 * Add new swapblk to biox, instantiating biox if necessary.
971 * Zero-fill reads are able to take a shortcut.
973 if (blk == SWAPBLK_NONE) {
975 * We can only get here if we are reading. Since
976 * we are at splvm() we can safely modify b_resid,
977 * even if chain ops are in progress.
979 bzero(data, PAGE_SIZE);
980 bp->b_resid -= PAGE_SIZE;
981 } else {
982 if (biox == NULL) {
983 /* XXX chain count > 4, wait to <= 4 */
985 bufx = getpbuf(NULL);
986 biox = &bufx->b_bio1;
987 cluster_append(nbio, bufx);
988 bufx->b_flags |= (bufx->b_flags & B_ORDERED);
989 bufx->b_cmd = bp->b_cmd;
990 biox->bio_done = swap_chain_iodone;
991 biox->bio_offset = (off_t)blk << PAGE_SHIFT;
992 biox->bio_caller_info1.cluster_parent = nbio;
993 biox_blkno = blk;
994 bufx->b_bcount = 0;
995 bufx->b_data = data;
997 bufx->b_bcount += PAGE_SIZE;
999 --count;
1000 ++start;
1001 data += PAGE_SIZE;
1005 * Flush out last buffer
1007 if (biox) {
1008 if (bufx->b_cmd == BUF_CMD_READ) {
1009 ++mycpu->gd_cnt.v_swapin;
1010 mycpu->gd_cnt.v_swappgsin += btoc(bufx->b_bcount);
1011 } else {
1012 ++mycpu->gd_cnt.v_swapout;
1013 mycpu->gd_cnt.v_swappgsout += btoc(bufx->b_bcount);
1014 bufx->b_dirtyend = bufx->b_bcount;
1016 KKASSERT(bufx->b_bcount);
1017 if (bufx->b_cmd != BUF_CMD_READ)
1018 bufx->b_dirtyend = bufx->b_bcount;
1019 /* biox, bufx = NULL */
1023 * Now initiate all the I/O. Be careful looping on our chain as
1024 * I/O's may complete while we are still initiating them.
1026 nbio->bio_caller_info2.cluster_tail = NULL;
1027 bufx = nbio->bio_caller_info1.cluster_head;
1029 while (bufx) {
1030 biox = &bufx->b_bio1;
1031 BUF_KERNPROC(bufx);
1032 bufx = bufx->b_cluster_next;
1033 vn_strategy(swapdev_vp, biox);
1037 * Completion of the cluster will also call biodone_chain(nbio).
1038 * We never call biodone(nbio) so we don't have to worry about
1039 * setting up a bio_done callback. It's handled in the sub-IO.
1041 /**/
1044 static void
1045 swap_chain_iodone(struct bio *biox)
1047 struct buf **nextp;
1048 struct buf *bufx; /* chained sub-buffer */
1049 struct bio *nbio; /* parent nbio with chain glue */
1050 struct buf *bp; /* original bp associated with nbio */
1051 int chain_empty;
1053 bufx = biox->bio_buf;
1054 nbio = biox->bio_caller_info1.cluster_parent;
1055 bp = nbio->bio_buf;
1058 * Update the original buffer
1060 KKASSERT(bp != NULL);
1061 if (bufx->b_flags & B_ERROR) {
1062 atomic_set_int(&bufx->b_flags, B_ERROR);
1063 bp->b_error = bufx->b_error;
1064 } else if (bufx->b_resid != 0) {
1065 atomic_set_int(&bufx->b_flags, B_ERROR);
1066 bp->b_error = EINVAL;
1067 } else {
1068 atomic_subtract_int(&bp->b_resid, bufx->b_bcount);
1072 * Remove us from the chain.
1074 spin_lock_wr(&bp->b_lock.lk_spinlock);
1075 nextp = &nbio->bio_caller_info1.cluster_head;
1076 while (*nextp != bufx) {
1077 KKASSERT(*nextp != NULL);
1078 nextp = &(*nextp)->b_cluster_next;
1080 *nextp = bufx->b_cluster_next;
1081 chain_empty = (nbio->bio_caller_info1.cluster_head == NULL);
1082 spin_unlock_wr(&bp->b_lock.lk_spinlock);
1085 * Clean up bufx. If the chain is now empty we finish out
1086 * the parent. Note that we may be racing other completions
1087 * so we must use the chain_empty status from above.
1089 if (chain_empty) {
1090 if (bp->b_resid != 0 && !(bp->b_flags & B_ERROR)) {
1091 atomic_set_int(&bp->b_flags, B_ERROR);
1092 bp->b_error = EINVAL;
1094 biodone_chain(nbio);
1096 relpbuf(bufx, NULL);
1100 * SWAP_PAGER_GETPAGES() - bring page in from swap
1102 * The requested page may have to be brought in from swap. Calculate the
1103 * swap block and bring in additional pages if possible. All pages must
1104 * have contiguous swap block assignments and reside in the same object.
1106 * The caller has a single vm_object_pip_add() reference prior to
1107 * calling us and we should return with the same.
1109 * The caller has BUSY'd the page. We should return with (*mpp) left busy,
1110 * and any additinal pages unbusied.
1112 * If the caller encounters a PG_RAM page it will pass it to us even though
1113 * it may be valid and dirty. We cannot overwrite the page in this case!
1114 * The case is used to allow us to issue pure read-aheads.
1116 * NOTE! XXX This code does not entirely pipeline yet due to the fact that
1117 * the PG_RAM page is validated at the same time as mreq. What we
1118 * really need to do is issue a separate read-ahead pbuf.
1120 static int
1121 swap_pager_getpage(vm_object_t object, vm_page_t *mpp, int seqaccess)
1123 struct buf *bp;
1124 struct bio *bio;
1125 vm_page_t mreq;
1126 vm_page_t m;
1127 vm_offset_t kva;
1128 daddr_t blk;
1129 int i;
1130 int j;
1131 int raonly;
1132 vm_page_t marray[XIO_INTERNAL_PAGES];
1134 mreq = *mpp;
1136 if (mreq->object != object) {
1137 panic("swap_pager_getpages: object mismatch %p/%p",
1138 object,
1139 mreq->object
1144 * We don't want to overwrite a fully valid page as it might be
1145 * dirty. This case can occur when e.g. vm_fault hits a perfectly
1146 * valid page with PG_RAM set.
1148 * In this case we see if the next page is a suitable page-in
1149 * candidate and if it is we issue read-ahead. PG_RAM will be
1150 * set on the last page of the read-ahead to continue the pipeline.
1152 if (mreq->valid == VM_PAGE_BITS_ALL) {
1153 if (swap_burst_read == 0 || mreq->pindex + 1 >= object->size)
1154 return(VM_PAGER_OK);
1155 crit_enter();
1156 blk = swp_pager_meta_ctl(object, mreq->pindex + 1, 0);
1157 if (blk == SWAPBLK_NONE) {
1158 crit_exit();
1159 return(VM_PAGER_OK);
1161 m = vm_page_lookup(object, mreq->pindex + 1);
1162 if (m == NULL) {
1163 m = vm_page_alloc(object, mreq->pindex + 1,
1164 VM_ALLOC_QUICK);
1165 if (m == NULL) {
1166 crit_exit();
1167 return(VM_PAGER_OK);
1169 } else {
1170 if ((m->flags & PG_BUSY) || m->busy || m->valid) {
1171 crit_exit();
1172 return(VM_PAGER_OK);
1174 vm_page_unqueue_nowakeup(m);
1175 vm_page_busy(m);
1177 mreq = m;
1178 raonly = 1;
1179 crit_exit();
1180 } else {
1181 raonly = 0;
1185 * Try to block-read contiguous pages from swap if sequential,
1186 * otherwise just read one page. Contiguous pages from swap must
1187 * reside within a single device stripe because the I/O cannot be
1188 * broken up across multiple stripes.
1190 * Note that blk and iblk can be SWAPBLK_NONE but the loop is
1191 * set up such that the case(s) are handled implicitly.
1193 crit_enter();
1194 blk = swp_pager_meta_ctl(mreq->object, mreq->pindex, 0);
1195 marray[0] = mreq;
1197 for (i = 1; swap_burst_read &&
1198 i < XIO_INTERNAL_PAGES &&
1199 mreq->pindex + i < object->size; ++i) {
1200 daddr_t iblk;
1202 iblk = swp_pager_meta_ctl(object, mreq->pindex + i, 0);
1203 if (iblk != blk + i)
1204 break;
1205 if ((blk ^ iblk) & dmmax_mask)
1206 break;
1207 m = vm_page_lookup(object, mreq->pindex + i);
1208 if (m == NULL) {
1209 m = vm_page_alloc(object, mreq->pindex + i,
1210 VM_ALLOC_QUICK);
1211 if (m == NULL)
1212 break;
1213 } else {
1214 if ((m->flags & PG_BUSY) || m->busy || m->valid)
1215 break;
1216 vm_page_unqueue_nowakeup(m);
1217 vm_page_busy(m);
1219 marray[i] = m;
1221 if (i > 1)
1222 vm_page_flag_set(marray[i - 1], PG_RAM);
1224 crit_exit();
1227 * If mreq is the requested page and we have nothing to do return
1228 * VM_PAGER_FAIL. If raonly is set mreq is just another read-ahead
1229 * page and must be cleaned up.
1231 if (blk == SWAPBLK_NONE) {
1232 KKASSERT(i == 1);
1233 if (raonly) {
1234 vnode_pager_freepage(mreq);
1235 return(VM_PAGER_OK);
1236 } else {
1237 return(VM_PAGER_FAIL);
1242 * map our page(s) into kva for input
1244 bp = getpbuf(&nsw_rcount);
1245 bio = &bp->b_bio1;
1246 kva = (vm_offset_t) bp->b_kvabase;
1247 bcopy(marray, bp->b_xio.xio_pages, i * sizeof(vm_page_t));
1248 pmap_qenter(kva, bp->b_xio.xio_pages, i);
1250 bp->b_data = (caddr_t)kva;
1251 bp->b_bcount = PAGE_SIZE * i;
1252 bp->b_xio.xio_npages = i;
1253 bio->bio_done = swp_pager_async_iodone;
1254 bio->bio_offset = (off_t)blk << PAGE_SHIFT;
1255 bio->bio_caller_info1.index = SWBIO_READ;
1258 * Set index. If raonly set the index beyond the array so all
1259 * the pages are treated the same, otherwise the original mreq is
1260 * at index 0.
1262 if (raonly)
1263 bio->bio_driver_info = (void *)(intptr_t)i;
1264 else
1265 bio->bio_driver_info = (void *)(intptr_t)0;
1267 for (j = 0; j < i; ++j)
1268 vm_page_flag_set(bp->b_xio.xio_pages[j], PG_SWAPINPROG);
1270 mycpu->gd_cnt.v_swapin++;
1271 mycpu->gd_cnt.v_swappgsin += bp->b_xio.xio_npages;
1274 * We still hold the lock on mreq, and our automatic completion routine
1275 * does not remove it.
1277 vm_object_pip_add(object, bp->b_xio.xio_npages);
1280 * perform the I/O. NOTE!!! bp cannot be considered valid after
1281 * this point because we automatically release it on completion.
1282 * Instead, we look at the one page we are interested in which we
1283 * still hold a lock on even through the I/O completion.
1285 * The other pages in our m[] array are also released on completion,
1286 * so we cannot assume they are valid anymore either.
1288 bp->b_cmd = BUF_CMD_READ;
1289 BUF_KERNPROC(bp);
1290 vn_strategy(swapdev_vp, bio);
1293 * Wait for the page we want to complete. PG_SWAPINPROG is always
1294 * cleared on completion. If an I/O error occurs, SWAPBLK_NONE
1295 * is set in the meta-data.
1297 * If this is a read-ahead only we return immediately without
1298 * waiting for I/O.
1300 if (raonly)
1301 return(VM_PAGER_OK);
1304 * Read-ahead includes originally requested page case.
1306 crit_enter();
1307 while ((mreq->flags & PG_SWAPINPROG) != 0) {
1308 vm_page_flag_set(mreq, PG_WANTED | PG_REFERENCED);
1309 mycpu->gd_cnt.v_intrans++;
1310 if (tsleep(mreq, 0, "swread", hz*20)) {
1311 kprintf(
1312 "swap_pager: indefinite wait buffer: "
1313 " offset: %lld, size: %ld\n",
1314 (long long)bio->bio_offset,
1315 (long)bp->b_bcount
1319 crit_exit();
1322 * mreq is left bussied after completion, but all the other pages
1323 * are freed. If we had an unrecoverable read error the page will
1324 * not be valid.
1326 if (mreq->valid != VM_PAGE_BITS_ALL)
1327 return(VM_PAGER_ERROR);
1328 else
1329 return(VM_PAGER_OK);
1332 * A final note: in a low swap situation, we cannot deallocate swap
1333 * and mark a page dirty here because the caller is likely to mark
1334 * the page clean when we return, causing the page to possibly revert
1335 * to all-zero's later.
1340 * swap_pager_putpages:
1342 * Assign swap (if necessary) and initiate I/O on the specified pages.
1344 * We support both OBJT_DEFAULT and OBJT_SWAP objects. DEFAULT objects
1345 * are automatically converted to SWAP objects.
1347 * In a low memory situation we may block in vn_strategy(), but the new
1348 * vm_page reservation system coupled with properly written VFS devices
1349 * should ensure that no low-memory deadlock occurs. This is an area
1350 * which needs work.
1352 * The parent has N vm_object_pip_add() references prior to
1353 * calling us and will remove references for rtvals[] that are
1354 * not set to VM_PAGER_PEND. We need to remove the rest on I/O
1355 * completion.
1357 * The parent has soft-busy'd the pages it passes us and will unbusy
1358 * those whos rtvals[] entry is not set to VM_PAGER_PEND on return.
1359 * We need to unbusy the rest on I/O completion.
1361 void
1362 swap_pager_putpages(vm_object_t object, vm_page_t *m, int count,
1363 boolean_t sync, int *rtvals)
1365 int i;
1366 int n = 0;
1368 if (count && m[0]->object != object) {
1369 panic("swap_pager_getpages: object mismatch %p/%p",
1370 object,
1371 m[0]->object
1376 * Step 1
1378 * Turn object into OBJT_SWAP
1379 * check for bogus sysops
1380 * force sync if not pageout process
1382 if (object->type == OBJT_DEFAULT)
1383 swp_pager_meta_convert(object);
1385 if (curthread != pagethread)
1386 sync = TRUE;
1389 * Step 2
1391 * Update nsw parameters from swap_async_max sysctl values.
1392 * Do not let the sysop crash the machine with bogus numbers.
1395 if (swap_async_max != nsw_wcount_async_max) {
1396 int n;
1399 * limit range
1401 if ((n = swap_async_max) > nswbuf / 2)
1402 n = nswbuf / 2;
1403 if (n < 1)
1404 n = 1;
1405 swap_async_max = n;
1408 * Adjust difference ( if possible ). If the current async
1409 * count is too low, we may not be able to make the adjustment
1410 * at this time.
1412 crit_enter();
1413 n -= nsw_wcount_async_max;
1414 if (nsw_wcount_async + n >= 0) {
1415 nsw_wcount_async += n;
1416 nsw_wcount_async_max += n;
1417 wakeup(&nsw_wcount_async);
1419 crit_exit();
1423 * Step 3
1425 * Assign swap blocks and issue I/O. We reallocate swap on the fly.
1426 * The page is left dirty until the pageout operation completes
1427 * successfully.
1430 for (i = 0; i < count; i += n) {
1431 struct buf *bp;
1432 struct bio *bio;
1433 daddr_t blk;
1434 int j;
1437 * Maximum I/O size is limited by a number of factors.
1440 n = min(BLIST_MAX_ALLOC, count - i);
1441 n = min(n, nsw_cluster_max);
1443 crit_enter();
1446 * Get biggest block of swap we can. If we fail, fall
1447 * back and try to allocate a smaller block. Don't go
1448 * overboard trying to allocate space if it would overly
1449 * fragment swap.
1451 while (
1452 (blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE &&
1453 n > 4
1455 n >>= 1;
1457 if (blk == SWAPBLK_NONE) {
1458 for (j = 0; j < n; ++j)
1459 rtvals[i+j] = VM_PAGER_FAIL;
1460 crit_exit();
1461 continue;
1465 * The I/O we are constructing cannot cross a physical
1466 * disk boundry in the swap stripe. Note: we are still
1467 * at splvm().
1469 if ((blk ^ (blk + n)) & dmmax_mask) {
1470 j = ((blk + dmmax) & dmmax_mask) - blk;
1471 swp_pager_freeswapspace(blk + j, n - j);
1472 n = j;
1476 * All I/O parameters have been satisfied, build the I/O
1477 * request and assign the swap space.
1480 if (sync == TRUE)
1481 bp = getpbuf(&nsw_wcount_sync);
1482 else
1483 bp = getpbuf(&nsw_wcount_async);
1484 bio = &bp->b_bio1;
1486 pmap_qenter((vm_offset_t)bp->b_data, &m[i], n);
1488 bp->b_bcount = PAGE_SIZE * n;
1489 bio->bio_offset = (off_t)blk << PAGE_SHIFT;
1491 for (j = 0; j < n; ++j) {
1492 vm_page_t mreq = m[i+j];
1494 swp_pager_meta_build(
1495 mreq->object,
1496 mreq->pindex,
1497 blk + j
1499 vm_page_dirty(mreq);
1500 rtvals[i+j] = VM_PAGER_OK;
1502 vm_page_flag_set(mreq, PG_SWAPINPROG);
1503 bp->b_xio.xio_pages[j] = mreq;
1505 bp->b_xio.xio_npages = n;
1507 mycpu->gd_cnt.v_swapout++;
1508 mycpu->gd_cnt.v_swappgsout += bp->b_xio.xio_npages;
1510 crit_exit();
1512 bp->b_dirtyoff = 0; /* req'd for NFS */
1513 bp->b_dirtyend = bp->b_bcount; /* req'd for NFS */
1514 bp->b_cmd = BUF_CMD_WRITE;
1515 bio->bio_caller_info1.index = SWBIO_WRITE;
1518 * asynchronous
1520 if (sync == FALSE) {
1521 bio->bio_done = swp_pager_async_iodone;
1522 BUF_KERNPROC(bp);
1523 vn_strategy(swapdev_vp, bio);
1525 for (j = 0; j < n; ++j)
1526 rtvals[i+j] = VM_PAGER_PEND;
1527 continue;
1531 * Issue synchrnously.
1533 * Wait for the sync I/O to complete, then update rtvals.
1534 * We just set the rtvals[] to VM_PAGER_PEND so we can call
1535 * our async completion routine at the end, thus avoiding a
1536 * double-free.
1538 bio->bio_caller_info1.index |= SWBIO_SYNC;
1539 bio->bio_done = biodone_sync;
1540 bio->bio_flags |= BIO_SYNC;
1541 vn_strategy(swapdev_vp, bio);
1542 biowait(bio, "swwrt");
1544 for (j = 0; j < n; ++j)
1545 rtvals[i+j] = VM_PAGER_PEND;
1548 * Now that we are through with the bp, we can call the
1549 * normal async completion, which frees everything up.
1551 swp_pager_async_iodone(bio);
1555 void
1556 swap_pager_newswap(void)
1558 swp_sizecheck();
1562 * swp_pager_async_iodone:
1564 * Completion routine for asynchronous reads and writes from/to swap.
1565 * Also called manually by synchronous code to finish up a bp.
1567 * For READ operations, the pages are PG_BUSY'd. For WRITE operations,
1568 * the pages are vm_page_t->busy'd. For READ operations, we PG_BUSY
1569 * unbusy all pages except the 'main' request page. For WRITE
1570 * operations, we vm_page_t->busy'd unbusy all pages ( we can do this
1571 * because we marked them all VM_PAGER_PEND on return from putpages ).
1573 * This routine may not block.
1575 static void
1576 swp_pager_async_iodone(struct bio *bio)
1578 struct buf *bp = bio->bio_buf;
1579 vm_object_t object = NULL;
1580 int i;
1581 int *nswptr;
1584 * report error
1586 if (bp->b_flags & B_ERROR) {
1587 kprintf(
1588 "swap_pager: I/O error - %s failed; offset %lld,"
1589 "size %ld, error %d\n",
1590 ((bio->bio_caller_info1.index & SWBIO_READ) ?
1591 "pagein" : "pageout"),
1592 (long long)bio->bio_offset,
1593 (long)bp->b_bcount,
1594 bp->b_error
1599 * set object, raise to splvm().
1601 if (bp->b_xio.xio_npages)
1602 object = bp->b_xio.xio_pages[0]->object;
1603 crit_enter();
1606 * remove the mapping for kernel virtual
1608 pmap_qremove((vm_offset_t)bp->b_data, bp->b_xio.xio_npages);
1611 * cleanup pages. If an error occurs writing to swap, we are in
1612 * very serious trouble. If it happens to be a disk error, though,
1613 * we may be able to recover by reassigning the swap later on. So
1614 * in this case we remove the m->swapblk assignment for the page
1615 * but do not free it in the rlist. The errornous block(s) are thus
1616 * never reallocated as swap. Redirty the page and continue.
1618 for (i = 0; i < bp->b_xio.xio_npages; ++i) {
1619 vm_page_t m = bp->b_xio.xio_pages[i];
1621 if (bp->b_flags & B_ERROR) {
1623 * If an error occurs I'd love to throw the swapblk
1624 * away without freeing it back to swapspace, so it
1625 * can never be used again. But I can't from an
1626 * interrupt.
1629 if (bio->bio_caller_info1.index & SWBIO_READ) {
1631 * When reading, reqpage needs to stay
1632 * locked for the parent, but all other
1633 * pages can be freed. We still want to
1634 * wakeup the parent waiting on the page,
1635 * though. ( also: pg_reqpage can be -1 and
1636 * not match anything ).
1638 * We have to wake specifically requested pages
1639 * up too because we cleared PG_SWAPINPROG and
1640 * someone may be waiting for that.
1642 * NOTE: for reads, m->dirty will probably
1643 * be overridden by the original caller of
1644 * getpages so don't play cute tricks here.
1646 * NOTE: We can't actually free the page from
1647 * here, because this is an interrupt. It
1648 * is not legal to mess with object->memq
1649 * from an interrupt. Deactivate the page
1650 * instead.
1653 m->valid = 0;
1654 vm_page_flag_clear(m, PG_ZERO);
1655 vm_page_flag_clear(m, PG_SWAPINPROG);
1658 * bio_driver_info holds the requested page
1659 * index.
1661 if (i != (int)(intptr_t)bio->bio_driver_info) {
1662 vm_page_deactivate(m);
1663 vm_page_wakeup(m);
1664 } else {
1665 vm_page_flash(m);
1668 * If i == bp->b_pager.pg_reqpage, do not wake
1669 * the page up. The caller needs to.
1671 } else {
1673 * If a write error occurs, reactivate page
1674 * so it doesn't clog the inactive list,
1675 * then finish the I/O.
1677 vm_page_dirty(m);
1678 vm_page_flag_clear(m, PG_SWAPINPROG);
1679 vm_page_activate(m);
1680 vm_page_io_finish(m);
1682 } else if (bio->bio_caller_info1.index & SWBIO_READ) {
1684 * NOTE: for reads, m->dirty will probably be
1685 * overridden by the original caller of getpages so
1686 * we cannot set them in order to free the underlying
1687 * swap in a low-swap situation. I don't think we'd
1688 * want to do that anyway, but it was an optimization
1689 * that existed in the old swapper for a time before
1690 * it got ripped out due to precisely this problem.
1692 * clear PG_ZERO in page.
1694 * If not the requested page then deactivate it.
1696 * Note that the requested page, reqpage, is left
1697 * busied, but we still have to wake it up. The
1698 * other pages are released (unbusied) by
1699 * vm_page_wakeup(). We do not set reqpage's
1700 * valid bits here, it is up to the caller.
1704 * NOTE: can't call pmap_clear_modify(m) from an
1705 * interrupt thread, the pmap code may have to map
1706 * non-kernel pmaps and currently asserts the case.
1708 /*pmap_clear_modify(m);*/
1709 m->valid = VM_PAGE_BITS_ALL;
1710 vm_page_undirty(m);
1711 vm_page_flag_clear(m, PG_ZERO | PG_SWAPINPROG);
1714 * We have to wake specifically requested pages
1715 * up too because we cleared PG_SWAPINPROG and
1716 * could be waiting for it in getpages. However,
1717 * be sure to not unbusy getpages specifically
1718 * requested page - getpages expects it to be
1719 * left busy.
1721 * bio_driver_info holds the requested page
1723 if (i != (int)(intptr_t)bio->bio_driver_info) {
1724 vm_page_deactivate(m);
1725 vm_page_wakeup(m);
1726 } else {
1727 vm_page_flash(m);
1729 } else {
1731 * Mark the page clean but do not mess with the
1732 * pmap-layer's modified state. That state should
1733 * also be clear since the caller protected the
1734 * page VM_PROT_READ, but allow the case.
1736 * We are in an interrupt, avoid pmap operations.
1738 * If we have a severe page deficit, deactivate the
1739 * page. Do not try to cache it (which would also
1740 * involve a pmap op), because the page might still
1741 * be read-heavy.
1743 vm_page_undirty(m);
1744 vm_page_flag_clear(m, PG_SWAPINPROG);
1745 vm_page_io_finish(m);
1746 if (vm_page_count_severe())
1747 vm_page_deactivate(m);
1748 #if 0
1749 if (!vm_page_count_severe() || !vm_page_try_to_cache(m))
1750 vm_page_protect(m, VM_PROT_READ);
1751 #endif
1756 * adjust pip. NOTE: the original parent may still have its own
1757 * pip refs on the object.
1760 if (object)
1761 vm_object_pip_wakeupn(object, bp->b_xio.xio_npages);
1764 * Release the physical I/O buffer.
1766 * NOTE: Due to synchronous operations in the write case b_cmd may
1767 * already be set to BUF_CMD_DONE and BIO_SYNC may have already
1768 * been cleared.
1770 if (bio->bio_caller_info1.index & SWBIO_READ)
1771 nswptr = &nsw_rcount;
1772 else if (bio->bio_caller_info1.index & SWBIO_SYNC)
1773 nswptr = &nsw_wcount_sync;
1774 else
1775 nswptr = &nsw_wcount_async;
1776 bp->b_cmd = BUF_CMD_DONE;
1777 relpbuf(bp, nswptr);
1778 crit_exit();
1781 /************************************************************************
1782 * SWAP META DATA *
1783 ************************************************************************
1785 * These routines manipulate the swap metadata stored in the
1786 * OBJT_SWAP object. All swp_*() routines must be called at
1787 * splvm() because swap can be freed up by the low level vm_page
1788 * code which might be called from interrupts beyond what splbio() covers.
1790 * Swap metadata is implemented with a global hash and not directly
1791 * linked into the object. Instead the object simply contains
1792 * appropriate tracking counters.
1796 * Lookup the swblock containing the specified swap block index.
1798 static __inline
1799 struct swblock *
1800 swp_pager_lookup(vm_object_t object, vm_pindex_t index)
1802 index &= ~SWAP_META_MASK;
1803 return (RB_LOOKUP(swblock_rb_tree, &object->swblock_root, index));
1807 * Remove a swblock from the RB tree.
1809 static __inline
1810 void
1811 swp_pager_remove(vm_object_t object, struct swblock *swap)
1813 RB_REMOVE(swblock_rb_tree, &object->swblock_root, swap);
1817 * Convert default object to swap object if necessary
1819 static void
1820 swp_pager_meta_convert(vm_object_t object)
1822 if (object->type == OBJT_DEFAULT) {
1823 object->type = OBJT_SWAP;
1824 KKASSERT(object->swblock_count == 0);
1826 if (object->handle != NULL) {
1827 TAILQ_INSERT_TAIL(
1828 NOBJLIST(object->handle),
1829 object,
1830 pager_object_list
1832 } else {
1833 TAILQ_INSERT_TAIL(
1834 &swap_pager_un_object_list,
1835 object,
1836 pager_object_list
1843 * SWP_PAGER_META_BUILD() - add swap block to swap meta data for object
1845 * We first convert the object to a swap object if it is a default
1846 * object. Vnode objects do not need to be converted.
1848 * The specified swapblk is added to the object's swap metadata. If
1849 * the swapblk is not valid, it is freed instead. Any previously
1850 * assigned swapblk is freed.
1852 static void
1853 swp_pager_meta_build(vm_object_t object, vm_pindex_t index, daddr_t swapblk)
1855 struct swblock *swap;
1856 struct swblock *oswap;
1858 KKASSERT(swapblk != SWAPBLK_NONE);
1861 * Convert object if necessary
1863 if (object->type == OBJT_DEFAULT)
1864 swp_pager_meta_convert(object);
1867 * Locate swblock. If not found create, but if we aren't adding
1868 * anything just return. If we run out of space in the map we wait
1869 * and, since the hash table may have changed, retry.
1871 retry:
1872 swap = swp_pager_lookup(object, index);
1874 if (swap == NULL) {
1875 int i;
1877 swap = zalloc(swap_zone);
1878 if (swap == NULL) {
1879 vm_wait(0);
1880 goto retry;
1882 swap->swb_index = index & ~SWAP_META_MASK;
1883 swap->swb_count = 0;
1885 ++object->swblock_count;
1887 for (i = 0; i < SWAP_META_PAGES; ++i)
1888 swap->swb_pages[i] = SWAPBLK_NONE;
1889 oswap = RB_INSERT(swblock_rb_tree, &object->swblock_root, swap);
1890 KKASSERT(oswap == NULL);
1894 * Delete prior contents of metadata
1897 index &= SWAP_META_MASK;
1899 if (swap->swb_pages[index] != SWAPBLK_NONE) {
1900 swp_pager_freeswapspace(swap->swb_pages[index], 1);
1901 --swap->swb_count;
1905 * Enter block into metadata
1907 swap->swb_pages[index] = swapblk;
1908 if (swapblk != SWAPBLK_NONE)
1909 ++swap->swb_count;
1913 * SWP_PAGER_META_FREE() - free a range of blocks in the object's swap metadata
1915 * The requested range of blocks is freed, with any associated swap
1916 * returned to the swap bitmap.
1918 * This routine will free swap metadata structures as they are cleaned
1919 * out. This routine does *NOT* operate on swap metadata associated
1920 * with resident pages.
1922 * This routine must be called at splvm()
1924 static void
1925 swp_pager_meta_free(vm_object_t object, vm_pindex_t index, daddr_t count)
1927 struct swblock *swap;
1929 if (object->type != OBJT_SWAP && object->type != OBJT_VNODE)
1930 return;
1932 while (count > 0) {
1933 swap = swp_pager_lookup(object, index);
1934 if (swap) {
1935 daddr_t v = swap->swb_pages[index & SWAP_META_MASK];
1937 if (v != SWAPBLK_NONE) {
1938 swp_pager_freeswapspace(v, 1);
1939 swap->swb_pages[index & SWAP_META_MASK] =
1940 SWAPBLK_NONE;
1941 if (--swap->swb_count == 0) {
1942 swp_pager_remove(object, swap);
1943 zfree(swap_zone, swap);
1944 --object->swblock_count;
1947 --count;
1948 ++index;
1949 } else {
1950 int n = SWAP_META_PAGES - (index & SWAP_META_MASK);
1951 count -= n;
1952 index += n;
1958 * SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object
1960 * This routine locates and destroys all swap metadata associated with
1961 * an object.
1963 * This routine must be called at splvm()
1965 static void
1966 swp_pager_meta_free_all(vm_object_t object)
1968 struct swblock *swap;
1969 int i;
1971 if (object->type != OBJT_SWAP && object->type != OBJT_VNODE)
1972 return;
1974 while ((swap = RB_ROOT(&object->swblock_root)) != NULL) {
1975 swp_pager_remove(object, swap);
1976 for (i = 0; i < SWAP_META_PAGES; ++i) {
1977 daddr_t v = swap->swb_pages[i];
1978 if (v != SWAPBLK_NONE) {
1979 --swap->swb_count;
1980 swp_pager_freeswapspace(v, 1);
1983 if (swap->swb_count != 0)
1984 panic("swap_pager_meta_free_all: swb_count != 0");
1985 zfree(swap_zone, swap);
1986 --object->swblock_count;
1988 KKASSERT(object->swblock_count == 0);
1992 * SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data.
1994 * This routine is capable of looking up, popping, or freeing
1995 * swapblk assignments in the swap meta data or in the vm_page_t.
1996 * The routine typically returns the swapblk being looked-up, or popped,
1997 * or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block
1998 * was invalid. This routine will automatically free any invalid
1999 * meta-data swapblks.
2001 * It is not possible to store invalid swapblks in the swap meta data
2002 * (other then a literal 'SWAPBLK_NONE'), so we don't bother checking.
2004 * When acting on a busy resident page and paging is in progress, we
2005 * have to wait until paging is complete but otherwise can act on the
2006 * busy page.
2008 * This routine must be called at splvm().
2010 * SWM_FREE remove and free swap block from metadata
2011 * SWM_POP remove from meta data but do not free.. pop it out
2013 static daddr_t
2014 swp_pager_meta_ctl(vm_object_t object, vm_pindex_t index, int flags)
2016 struct swblock *swap;
2017 daddr_t r1;
2020 * The meta data only exists of the object is OBJT_SWAP
2021 * and even then might not be allocated yet.
2024 if (object->type != OBJT_SWAP && object->type != OBJT_VNODE)
2025 return(SWAPBLK_NONE);
2027 r1 = SWAPBLK_NONE;
2028 swap = swp_pager_lookup(object, index);
2030 if (swap != NULL) {
2031 index &= SWAP_META_MASK;
2032 r1 = swap->swb_pages[index];
2034 if (r1 != SWAPBLK_NONE) {
2035 if (flags & SWM_FREE) {
2036 swp_pager_freeswapspace(r1, 1);
2037 r1 = SWAPBLK_NONE;
2039 if (flags & (SWM_FREE|SWM_POP)) {
2040 swap->swb_pages[index] = SWAPBLK_NONE;
2041 if (--swap->swb_count == 0) {
2042 swp_pager_remove(object, swap);
2043 zfree(swap_zone, swap);
2044 --object->swblock_count;
2049 return(r1);