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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>
132 #include <sys/buf2.h>
133 #include <vm/vm_page2.h>
135 #define SWM_FREE 0x02 /* free, period */
136 #define SWM_POP 0x04 /* pop out */
138 #define AUTOCHAINDONE ((struct buf *)(intptr_t)-1)
141 * vm_swap_size is in page-sized chunks now. It was DEV_BSIZE'd chunks
142 * in the old system.
145 extern int vm_swap_size; /* number of free swap blocks, in pages */
147 int swap_pager_full; /* swap space exhaustion (task killing) */
148 static int swap_pager_almost_full; /* swap space exhaustion (w/ hysteresis)*/
149 static int nsw_rcount; /* free read buffers */
150 static int nsw_wcount_sync; /* limit write buffers / synchronous */
151 static int nsw_wcount_async; /* limit write buffers / asynchronous */
152 static int nsw_wcount_async_max;/* assigned maximum */
153 static int nsw_cluster_max; /* maximum VOP I/O allowed */
154 static int sw_alloc_interlock; /* swap pager allocation interlock */
156 struct blist *swapblist;
157 static struct swblock **swhash;
158 static int swhash_mask;
159 static int swap_async_max = 4; /* maximum in-progress async I/O's */
161 extern struct vnode *swapdev_vp; /* from vm_swap.c */
163 SYSCTL_INT(_vm, OID_AUTO, swap_async_max,
164 CTLFLAG_RW, &swap_async_max, 0, "Maximum running async swap ops");
167 * "named" and "unnamed" anon region objects. Try to reduce the overhead
168 * of searching a named list by hashing it just a little.
171 #define NOBJLISTS 8
173 #define NOBJLIST(handle) \
174 (&swap_pager_object_list[((int)(intptr_t)handle >> 4) & (NOBJLISTS-1)])
176 static struct pagerlst swap_pager_object_list[NOBJLISTS];
177 struct pagerlst swap_pager_un_object_list;
178 vm_zone_t swap_zone;
181 * pagerops for OBJT_SWAP - "swap pager". Some ops are also global procedure
182 * calls hooked from other parts of the VM system and do not appear here.
183 * (see vm/swap_pager.h).
186 static vm_object_t
187 swap_pager_alloc (void *handle, off_t size,
188 vm_prot_t prot, off_t offset);
189 static void swap_pager_dealloc (vm_object_t object);
190 static int swap_pager_getpages (vm_object_t, vm_page_t *, int, int);
191 static void swap_pager_init (void);
192 static void swap_pager_unswapped (vm_page_t);
193 static void swap_pager_strategy (vm_object_t, struct bio *);
194 static void swap_chain_iodone(struct bio *biox);
196 struct pagerops swappagerops = {
197 swap_pager_init, /* early system initialization of pager */
198 swap_pager_alloc, /* allocate an OBJT_SWAP object */
199 swap_pager_dealloc, /* deallocate an OBJT_SWAP object */
200 swap_pager_getpages, /* pagein */
201 swap_pager_putpages, /* pageout */
202 swap_pager_haspage, /* get backing store status for page */
203 swap_pager_unswapped, /* remove swap related to page */
204 swap_pager_strategy /* pager strategy call */
208 * dmmax is in page-sized chunks with the new swap system. It was
209 * dev-bsized chunks in the old. dmmax is always a power of 2.
211 * swap_*() routines are externally accessible. swp_*() routines are
212 * internal.
215 int dmmax;
216 static int dmmax_mask;
217 int nswap_lowat = 128; /* in pages, swap_pager_almost_full warn */
218 int nswap_hiwat = 512; /* in pages, swap_pager_almost_full warn */
220 static __inline void swp_sizecheck (void);
221 static void swp_pager_sync_iodone (struct bio *bio);
222 static void swp_pager_async_iodone (struct bio *bio);
225 * Swap bitmap functions
228 static __inline void swp_pager_freeswapspace (daddr_t blk, int npages);
229 static __inline daddr_t swp_pager_getswapspace (int npages);
232 * Metadata functions
235 static void swp_pager_meta_build (vm_object_t, vm_pindex_t, daddr_t);
236 static void swp_pager_meta_free (vm_object_t, vm_pindex_t, daddr_t);
237 static void swp_pager_meta_free_all (vm_object_t);
238 static daddr_t swp_pager_meta_ctl (vm_object_t, vm_pindex_t, int);
241 * SWP_SIZECHECK() - update swap_pager_full indication
243 * update the swap_pager_almost_full indication and warn when we are
244 * about to run out of swap space, using lowat/hiwat hysteresis.
246 * Clear swap_pager_full ( task killing ) indication when lowat is met.
248 * No restrictions on call
249 * This routine may not block.
250 * This routine must be called at splvm()
253 static __inline void
254 swp_sizecheck(void)
256 if (vm_swap_size < nswap_lowat) {
257 if (swap_pager_almost_full == 0) {
258 kprintf("swap_pager: out of swap space\n");
259 swap_pager_almost_full = 1;
261 } else {
262 swap_pager_full = 0;
263 if (vm_swap_size > nswap_hiwat)
264 swap_pager_almost_full = 0;
269 * SWAP_PAGER_INIT() - initialize the swap pager!
271 * Expected to be started from system init. NOTE: This code is run
272 * before much else so be careful what you depend on. Most of the VM
273 * system has yet to be initialized at this point.
276 static void
277 swap_pager_init(void)
280 * Initialize object lists
282 int i;
284 for (i = 0; i < NOBJLISTS; ++i)
285 TAILQ_INIT(&swap_pager_object_list[i]);
286 TAILQ_INIT(&swap_pager_un_object_list);
289 * Device Stripe, in PAGE_SIZE'd blocks
292 dmmax = SWB_NPAGES * 2;
293 dmmax_mask = ~(dmmax - 1);
297 * SWAP_PAGER_SWAP_INIT() - swap pager initialization from pageout process
299 * Expected to be started from pageout process once, prior to entering
300 * its main loop.
303 void
304 swap_pager_swap_init(void)
306 int n, n2;
309 * Number of in-transit swap bp operations. Don't
310 * exhaust the pbufs completely. Make sure we
311 * initialize workable values (0 will work for hysteresis
312 * but it isn't very efficient).
314 * The nsw_cluster_max is constrained by the number of pages an XIO
315 * holds, i.e., (MAXPHYS/PAGE_SIZE) and our locally defined
316 * MAX_PAGEOUT_CLUSTER. Also be aware that swap ops are
317 * constrained by the swap device interleave stripe size.
319 * Currently we hardwire nsw_wcount_async to 4. This limit is
320 * designed to prevent other I/O from having high latencies due to
321 * our pageout I/O. The value 4 works well for one or two active swap
322 * devices but is probably a little low if you have more. Even so,
323 * a higher value would probably generate only a limited improvement
324 * with three or four active swap devices since the system does not
325 * typically have to pageout at extreme bandwidths. We will want
326 * at least 2 per swap devices, and 4 is a pretty good value if you
327 * have one NFS swap device due to the command/ack latency over NFS.
328 * So it all works out pretty well.
331 nsw_cluster_max = min((MAXPHYS/PAGE_SIZE), MAX_PAGEOUT_CLUSTER);
333 nsw_rcount = (nswbuf + 1) / 2;
334 nsw_wcount_sync = (nswbuf + 3) / 4;
335 nsw_wcount_async = 4;
336 nsw_wcount_async_max = nsw_wcount_async;
339 * Initialize our zone. Right now I'm just guessing on the number
340 * we need based on the number of pages in the system. Each swblock
341 * can hold 16 pages, so this is probably overkill. This reservation
342 * is typically limited to around 32MB by default.
344 n = vmstats.v_page_count / 2;
345 if (maxswzone && n > maxswzone / sizeof(struct swblock))
346 n = maxswzone / sizeof(struct swblock);
347 n2 = n;
349 do {
350 swap_zone = zinit(
351 "SWAPMETA",
352 sizeof(struct swblock),
354 ZONE_INTERRUPT,
356 if (swap_zone != NULL)
357 break;
359 * if the allocation failed, try a zone two thirds the
360 * size of the previous attempt.
362 n -= ((n + 2) / 3);
363 } while (n > 0);
365 if (swap_zone == NULL)
366 panic("swap_pager_swap_init: swap_zone == NULL");
367 if (n2 != n)
368 kprintf("Swap zone entries reduced from %d to %d.\n", n2, n);
369 n2 = n;
372 * Initialize our meta-data hash table. The swapper does not need to
373 * be quite as efficient as the VM system, so we do not use an
374 * oversized hash table.
376 * n: size of hash table, must be power of 2
377 * swhash_mask: hash table index mask
380 for (n = 1; n < n2 / 8; n *= 2)
383 swhash = kmalloc(sizeof(struct swblock *) * n, M_VMPGDATA,
384 M_WAITOK | M_ZERO);
386 swhash_mask = n - 1;
390 * SWAP_PAGER_ALLOC() - allocate a new OBJT_SWAP VM object and instantiate
391 * its metadata structures.
393 * This routine is called from the mmap and fork code to create a new
394 * OBJT_SWAP object. We do this by creating an OBJT_DEFAULT object
395 * and then converting it with swp_pager_meta_build().
397 * This routine may block in vm_object_allocate() and create a named
398 * object lookup race, so we must interlock. We must also run at
399 * splvm() for the object lookup to handle races with interrupts, but
400 * we do not have to maintain splvm() in between the lookup and the
401 * add because (I believe) it is not possible to attempt to create
402 * a new swap object w/handle when a default object with that handle
403 * already exists.
406 static vm_object_t
407 swap_pager_alloc(void *handle, off_t size, vm_prot_t prot, off_t offset)
409 vm_object_t object;
411 if (handle) {
413 * Reference existing named region or allocate new one. There
414 * should not be a race here against swp_pager_meta_build()
415 * as called from vm_page_remove() in regards to the lookup
416 * of the handle.
419 while (sw_alloc_interlock) {
420 sw_alloc_interlock = -1;
421 tsleep(&sw_alloc_interlock, 0, "swpalc", 0);
423 sw_alloc_interlock = 1;
425 object = vm_pager_object_lookup(NOBJLIST(handle), handle);
427 if (object != NULL) {
428 vm_object_reference(object);
429 } else {
430 object = vm_object_allocate(OBJT_DEFAULT,
431 OFF_TO_IDX(offset + PAGE_MASK + size));
432 object->handle = handle;
434 swp_pager_meta_build(object, 0, SWAPBLK_NONE);
437 if (sw_alloc_interlock < 0)
438 wakeup(&sw_alloc_interlock);
440 sw_alloc_interlock = 0;
441 } else {
442 object = vm_object_allocate(OBJT_DEFAULT,
443 OFF_TO_IDX(offset + PAGE_MASK + size));
445 swp_pager_meta_build(object, 0, SWAPBLK_NONE);
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 temporarily
566 * in order to perform the metadata removal.
569 void
570 swap_pager_freespace(vm_object_t object, vm_pindex_t start, vm_size_t size)
572 crit_enter();
573 swp_pager_meta_free(object, start, size);
574 crit_exit();
578 * SWAP_PAGER_RESERVE() - reserve swap blocks in object
580 * Assigns swap blocks to the specified range within the object. The
581 * swap blocks are not zerod. Any previous swap assignment is destroyed.
583 * Returns 0 on success, -1 on failure.
587 swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_size_t size)
589 int n = 0;
590 daddr_t blk = SWAPBLK_NONE;
591 vm_pindex_t beg = start; /* save start index */
593 crit_enter();
594 while (size) {
595 if (n == 0) {
596 n = BLIST_MAX_ALLOC;
597 while ((blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE) {
598 n >>= 1;
599 if (n == 0) {
600 swp_pager_meta_free(object, beg, start - beg);
601 crit_exit();
602 return(-1);
606 swp_pager_meta_build(object, start, blk);
607 --size;
608 ++start;
609 ++blk;
610 --n;
612 swp_pager_meta_free(object, start, n);
613 crit_exit();
614 return(0);
618 * SWAP_PAGER_COPY() - copy blocks from source pager to destination pager
619 * and destroy the source.
621 * Copy any valid swapblks from the source to the destination. In
622 * cases where both the source and destination have a valid swapblk,
623 * we keep the destination's.
625 * This routine is allowed to block. It may block allocating metadata
626 * indirectly through swp_pager_meta_build() or if paging is still in
627 * progress on the source.
629 * This routine can be called at any spl
631 * XXX vm_page_collapse() kinda expects us not to block because we
632 * supposedly do not need to allocate memory, but for the moment we
633 * *may* have to get a little memory from the zone allocator, but
634 * it is taken from the interrupt memory. We should be ok.
636 * The source object contains no vm_page_t's (which is just as well)
638 * The source object is of type OBJT_SWAP.
640 * The source and destination objects must be locked or
641 * inaccessible (XXX are they ?)
644 void
645 swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject,
646 vm_pindex_t offset, int destroysource)
648 vm_pindex_t i;
650 crit_enter();
653 * If destroysource is set, we remove the source object from the
654 * swap_pager internal queue now.
657 if (destroysource) {
658 if (srcobject->handle == NULL) {
659 TAILQ_REMOVE(
660 &swap_pager_un_object_list,
661 srcobject,
662 pager_object_list
664 } else {
665 TAILQ_REMOVE(
666 NOBJLIST(srcobject->handle),
667 srcobject,
668 pager_object_list
674 * transfer source to destination.
677 for (i = 0; i < dstobject->size; ++i) {
678 daddr_t dstaddr;
681 * Locate (without changing) the swapblk on the destination,
682 * unless it is invalid in which case free it silently, or
683 * if the destination is a resident page, in which case the
684 * source is thrown away.
687 dstaddr = swp_pager_meta_ctl(dstobject, i, 0);
689 if (dstaddr == SWAPBLK_NONE) {
691 * Destination has no swapblk and is not resident,
692 * copy source.
694 daddr_t srcaddr;
696 srcaddr = swp_pager_meta_ctl(
697 srcobject,
698 i + offset,
699 SWM_POP
702 if (srcaddr != SWAPBLK_NONE)
703 swp_pager_meta_build(dstobject, i, srcaddr);
704 } else {
706 * Destination has valid swapblk or it is represented
707 * by a resident page. We destroy the sourceblock.
710 swp_pager_meta_ctl(srcobject, i + offset, SWM_FREE);
715 * Free left over swap blocks in source.
717 * We have to revert the type to OBJT_DEFAULT so we do not accidently
718 * double-remove the object from the swap queues.
721 if (destroysource) {
722 swp_pager_meta_free_all(srcobject);
724 * Reverting the type is not necessary, the caller is going
725 * to destroy srcobject directly, but I'm doing it here
726 * for consistency since we've removed the object from its
727 * queues.
729 srcobject->type = OBJT_DEFAULT;
731 crit_exit();
735 * SWAP_PAGER_HASPAGE() - determine if we have good backing store for
736 * the requested page.
738 * We determine whether good backing store exists for the requested
739 * page and return TRUE if it does, FALSE if it doesn't.
741 * If TRUE, we also try to determine how much valid, contiguous backing
742 * store exists before and after the requested page within a reasonable
743 * distance. We do not try to restrict it to the swap device stripe
744 * (that is handled in getpages/putpages). It probably isn't worth
745 * doing here.
748 boolean_t
749 swap_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
750 int *after)
752 daddr_t blk0;
755 * do we have good backing store at the requested index ?
758 crit_enter();
759 blk0 = swp_pager_meta_ctl(object, pindex, 0);
761 if (blk0 == SWAPBLK_NONE) {
762 crit_exit();
763 if (before)
764 *before = 0;
765 if (after)
766 *after = 0;
767 return (FALSE);
771 * find backwards-looking contiguous good backing store
774 if (before != NULL) {
775 int i;
777 for (i = 1; i < (SWB_NPAGES/2); ++i) {
778 daddr_t blk;
780 if (i > pindex)
781 break;
782 blk = swp_pager_meta_ctl(object, pindex - i, 0);
783 if (blk != blk0 - i)
784 break;
786 *before = (i - 1);
790 * find forward-looking contiguous good backing store
793 if (after != NULL) {
794 int i;
796 for (i = 1; i < (SWB_NPAGES/2); ++i) {
797 daddr_t blk;
799 blk = swp_pager_meta_ctl(object, pindex + i, 0);
800 if (blk != blk0 + i)
801 break;
803 *after = (i - 1);
805 crit_exit();
806 return (TRUE);
810 * SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page
812 * This removes any associated swap backing store, whether valid or
813 * not, from the page.
815 * This routine is typically called when a page is made dirty, at
816 * which point any associated swap can be freed. MADV_FREE also
817 * calls us in a special-case situation
819 * NOTE!!! If the page is clean and the swap was valid, the caller
820 * should make the page dirty before calling this routine. This routine
821 * does NOT change the m->dirty status of the page. Also: MADV_FREE
822 * depends on it.
824 * This routine may not block
825 * This routine must be called at splvm()
828 static void
829 swap_pager_unswapped(vm_page_t m)
831 swp_pager_meta_ctl(m->object, m->pindex, SWM_FREE);
835 * SWAP_PAGER_STRATEGY() - read, write, free blocks
837 * This implements the vm_pager_strategy() interface to swap and allows
838 * other parts of the system to directly access swap as backing store
839 * through vm_objects of type OBJT_SWAP. This is intended to be a
840 * cacheless interface ( i.e. caching occurs at higher levels ).
841 * Therefore we do not maintain any resident pages. All I/O goes
842 * directly to and from the swap device.
844 * We currently attempt to run I/O synchronously or asynchronously as
845 * the caller requests. This isn't perfect because we loose error
846 * sequencing when we run multiple ops in parallel to satisfy a request.
847 * But this is swap, so we let it all hang out.
850 static void
851 swap_pager_strategy(vm_object_t object, struct bio *bio)
853 struct buf *bp = bio->bio_buf;
854 struct bio *nbio;
855 vm_pindex_t start;
856 vm_pindex_t biox_blkno = 0;
857 int count;
858 char *data;
859 struct bio *biox = NULL;
860 struct buf *bufx = NULL;
861 struct bio_track *track;
864 * tracking for swapdev vnode I/Os
866 if (bp->b_cmd == BUF_CMD_READ)
867 track = &swapdev_vp->v_track_read;
868 else
869 track = &swapdev_vp->v_track_write;
871 if (bp->b_bcount & PAGE_MASK) {
872 bp->b_error = EINVAL;
873 bp->b_flags |= B_ERROR | B_INVAL;
874 biodone(bio);
875 kprintf("swap_pager_strategy: bp %p offset %lld size %d, not page bounded\n", bp, bio->bio_offset, (int)bp->b_bcount);
876 return;
880 * Clear error indication, initialize page index, count, data pointer.
882 bp->b_error = 0;
883 bp->b_flags &= ~B_ERROR;
884 bp->b_resid = bp->b_bcount;
886 start = (vm_pindex_t)(bio->bio_offset >> PAGE_SHIFT);
887 count = howmany(bp->b_bcount, PAGE_SIZE);
888 data = bp->b_data;
890 crit_enter();
893 * Deal with BUF_CMD_FREEBLKS
895 if (bp->b_cmd == BUF_CMD_FREEBLKS) {
897 * FREE PAGE(s) - destroy underlying swap that is no longer
898 * needed.
900 swp_pager_meta_free(object, start, count);
901 crit_exit();
902 bp->b_resid = 0;
903 biodone(bio);
904 return;
908 * We need to be able to create a new cluster of I/O's. We cannot
909 * use the caller fields of the passed bio so push a new one.
911 * Because nbio is just a placeholder for the cluster links,
912 * we can biodone() the original bio instead of nbio to make
913 * things a bit more efficient.
915 nbio = push_bio(bio);
916 nbio->bio_offset = bio->bio_offset;
917 nbio->bio_caller_info1.cluster_head = NULL;
918 nbio->bio_caller_info2.cluster_tail = NULL;
921 * Execute read or write
924 while (count > 0) {
925 daddr_t blk;
928 * Obtain block. If block not found and writing, allocate a
929 * new block and build it into the object.
932 blk = swp_pager_meta_ctl(object, start, 0);
933 if ((blk == SWAPBLK_NONE) && bp->b_cmd != BUF_CMD_READ) {
934 blk = swp_pager_getswapspace(1);
935 if (blk == SWAPBLK_NONE) {
936 bp->b_error = ENOMEM;
937 bp->b_flags |= B_ERROR;
938 break;
940 swp_pager_meta_build(object, start, blk);
944 * Do we have to flush our current collection? Yes if:
946 * - no swap block at this index
947 * - swap block is not contiguous
948 * - we cross a physical disk boundry in the
949 * stripe.
952 if (
953 biox && (biox_blkno + btoc(bufx->b_bcount) != blk ||
954 ((biox_blkno ^ blk) & dmmax_mask)
957 crit_exit();
958 if (bp->b_cmd == BUF_CMD_READ) {
959 ++mycpu->gd_cnt.v_swapin;
960 mycpu->gd_cnt.v_swappgsin += btoc(bufx->b_bcount);
961 } else {
962 ++mycpu->gd_cnt.v_swapout;
963 mycpu->gd_cnt.v_swappgsout += btoc(bufx->b_bcount);
964 bufx->b_dirtyend = bufx->b_bcount;
968 * Flush the biox to the swap device.
970 if (bufx->b_bcount) {
971 if (bufx->b_cmd != BUF_CMD_READ)
972 bufx->b_dirtyend = bufx->b_bcount;
973 BUF_KERNPROC(bufx);
974 vn_strategy(swapdev_vp, biox);
975 } else {
976 biodone(biox);
978 crit_enter();
979 biox = NULL;
980 bufx = NULL;
984 * Add new swapblk to biox, instantiating biox if necessary.
985 * Zero-fill reads are able to take a shortcut.
987 if (blk == SWAPBLK_NONE) {
989 * We can only get here if we are reading. Since
990 * we are at splvm() we can safely modify b_resid,
991 * even if chain ops are in progress.
993 bzero(data, PAGE_SIZE);
994 bp->b_resid -= PAGE_SIZE;
995 } else {
996 if (biox == NULL) {
997 /* XXX chain count > 4, wait to <= 4 */
999 bufx = getpbuf(NULL);
1000 biox = &bufx->b_bio1;
1001 cluster_append(nbio, bufx);
1002 bufx->b_flags |= (bufx->b_flags & B_ORDERED) |
1003 B_ASYNC;
1004 bufx->b_cmd = bp->b_cmd;
1005 biox->bio_done = swap_chain_iodone;
1006 biox->bio_offset = (off_t)blk << PAGE_SHIFT;
1007 biox->bio_caller_info1.cluster_parent = nbio;
1008 biox_blkno = blk;
1009 bufx->b_bcount = 0;
1010 bufx->b_data = data;
1012 bufx->b_bcount += PAGE_SIZE;
1014 --count;
1015 ++start;
1016 data += PAGE_SIZE;
1020 * Flush out last buffer
1022 crit_exit();
1024 if (biox) {
1025 if ((bp->b_flags & B_ASYNC) == 0)
1026 bufx->b_flags &= ~B_ASYNC;
1027 if (bufx->b_cmd == BUF_CMD_READ) {
1028 ++mycpu->gd_cnt.v_swapin;
1029 mycpu->gd_cnt.v_swappgsin += btoc(bufx->b_bcount);
1030 } else {
1031 ++mycpu->gd_cnt.v_swapout;
1032 mycpu->gd_cnt.v_swappgsout += btoc(bufx->b_bcount);
1033 bufx->b_dirtyend = bufx->b_bcount;
1035 if (bufx->b_bcount) {
1036 if (bufx->b_cmd != BUF_CMD_READ)
1037 bufx->b_dirtyend = bufx->b_bcount;
1038 BUF_KERNPROC(bufx);
1039 vn_strategy(swapdev_vp, biox);
1040 } else {
1041 biodone(biox);
1043 /* biox, bufx = NULL */
1047 * Wait for completion. Now that we are no longer using
1048 * cluster_append, use the cluster_tail field to indicate
1049 * auto-completion if there are still I/O's in progress.
1051 if (bp->b_flags & B_ASYNC) {
1052 crit_enter();
1053 if (nbio->bio_caller_info1.cluster_head == NULL) {
1054 biodone(bio);
1055 } else {
1056 nbio->bio_caller_info2.cluster_tail = AUTOCHAINDONE;
1058 crit_exit();
1059 } else {
1060 crit_enter();
1061 while (nbio->bio_caller_info1.cluster_head != NULL) {
1062 bp->b_flags |= B_WANT;
1063 tsleep(bp, 0, "bpchain", 0);
1065 if (bp->b_resid != 0 && !(bp->b_flags & B_ERROR)) {
1066 bp->b_flags |= B_ERROR;
1067 bp->b_error = EINVAL;
1069 biodone(bio);
1070 crit_exit();
1074 static void
1075 swap_chain_iodone(struct bio *biox)
1077 struct buf **nextp;
1078 struct buf *bufx; /* chained sub-buffer */
1079 struct bio *nbio; /* parent nbio with chain glue */
1080 struct buf *bp; /* original bp associated with nbio */
1082 bufx = biox->bio_buf;
1083 nbio = biox->bio_caller_info1.cluster_parent;
1084 bp = nbio->bio_buf;
1087 * Update the original buffer
1089 KKASSERT(bp != NULL);
1090 if (bufx->b_flags & B_ERROR) {
1091 bp->b_flags |= B_ERROR;
1092 bp->b_error = bufx->b_error;
1093 } else if (bufx->b_resid != 0) {
1094 bp->b_flags |= B_ERROR;
1095 bp->b_error = EINVAL;
1096 } else {
1097 bp->b_resid -= bufx->b_bcount;
1101 * Remove us from the chain. It is sufficient to clean up
1102 * cluster_head. Once the chain is operational cluster_tail
1103 * may be used to indicate AUTOCHAINDONE. Note that I/O's
1104 * can complete while the swap system is still appending new
1105 * BIOs to the chain.
1107 nextp = &nbio->bio_caller_info1.cluster_head;
1108 while (*nextp != bufx) {
1109 KKASSERT(*nextp != NULL);
1110 nextp = &(*nextp)->b_cluster_next;
1112 *nextp = bufx->b_cluster_next;
1113 if (bp->b_flags & B_WANT) {
1114 bp->b_flags &= ~B_WANT;
1115 wakeup(bp);
1119 * Clean up bufx. If this was the last buffer in the chain
1120 * and AUTOCHAINDONE was set, finish off the original I/O
1121 * as well.
1123 * nbio was just a fake BIO layer to hold the cluster links,
1124 * we can issue the biodone() on the layer above it.
1126 if (nbio->bio_caller_info1.cluster_head == NULL &&
1127 nbio->bio_caller_info2.cluster_tail == AUTOCHAINDONE
1129 nbio->bio_caller_info2.cluster_tail = NULL;
1130 if (bp->b_resid != 0 && !(bp->b_flags & B_ERROR)) {
1131 bp->b_flags |= B_ERROR;
1132 bp->b_error = EINVAL;
1134 biodone(nbio->bio_prev);
1136 bufx->b_flags &= ~B_ASYNC;
1137 relpbuf(bufx, NULL);
1141 * SWAP_PAGER_GETPAGES() - bring pages in from swap
1143 * Attempt to retrieve (m, count) pages from backing store, but make
1144 * sure we retrieve at least m[reqpage]. We try to load in as large
1145 * a chunk surrounding m[reqpage] as is contiguous in swap and which
1146 * belongs to the same object.
1148 * The code is designed for asynchronous operation and
1149 * immediate-notification of 'reqpage' but tends not to be
1150 * used that way. Please do not optimize-out this algorithmic
1151 * feature, I intend to improve on it in the future.
1153 * The parent has a single vm_object_pip_add() reference prior to
1154 * calling us and we should return with the same.
1156 * The parent has BUSY'd the pages. We should return with 'm'
1157 * left busy, but the others adjusted.
1160 static int
1161 swap_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage)
1163 struct buf *bp;
1164 struct bio *bio;
1165 vm_page_t mreq;
1166 int i;
1167 int j;
1168 daddr_t blk;
1169 vm_offset_t kva;
1170 vm_pindex_t lastpindex;
1172 mreq = m[reqpage];
1174 if (mreq->object != object) {
1175 panic("swap_pager_getpages: object mismatch %p/%p",
1176 object,
1177 mreq->object
1182 * Calculate range to retrieve. The pages have already been assigned
1183 * their swapblks. We require a *contiguous* range that falls entirely
1184 * within a single device stripe. If we do not supply it, bad things
1185 * happen. Note that blk, iblk & jblk can be SWAPBLK_NONE, but the
1186 * loops are set up such that the case(s) are handled implicitly.
1188 * The swp_*() calls must be made at splvm(). vm_page_free() does
1189 * not need to be, but it will go a little faster if it is.
1191 crit_enter();
1192 blk = swp_pager_meta_ctl(mreq->object, mreq->pindex, 0);
1194 for (i = reqpage - 1; i >= 0; --i) {
1195 daddr_t iblk;
1197 iblk = swp_pager_meta_ctl(m[i]->object, m[i]->pindex, 0);
1198 if (blk != iblk + (reqpage - i))
1199 break;
1200 if ((blk ^ iblk) & dmmax_mask)
1201 break;
1203 ++i;
1205 for (j = reqpage + 1; j < count; ++j) {
1206 daddr_t jblk;
1208 jblk = swp_pager_meta_ctl(m[j]->object, m[j]->pindex, 0);
1209 if (blk != jblk - (j - reqpage))
1210 break;
1211 if ((blk ^ jblk) & dmmax_mask)
1212 break;
1216 * free pages outside our collection range. Note: we never free
1217 * mreq, it must remain busy throughout.
1221 int k;
1223 for (k = 0; k < i; ++k)
1224 vm_page_free(m[k]);
1225 for (k = j; k < count; ++k)
1226 vm_page_free(m[k]);
1228 crit_exit();
1232 * Return VM_PAGER_FAIL if we have nothing to do. Return mreq
1233 * still busy, but the others unbusied.
1236 if (blk == SWAPBLK_NONE)
1237 return(VM_PAGER_FAIL);
1240 * Get a swap buffer header to perform the IO
1243 bp = getpbuf(&nsw_rcount);
1244 bio = &bp->b_bio1;
1245 kva = (vm_offset_t) bp->b_data;
1248 * map our page(s) into kva for input
1251 pmap_qenter(kva, m + i, j - i);
1253 bp->b_data = (caddr_t) kva;
1254 bp->b_bcount = PAGE_SIZE * (j - i);
1255 bio->bio_done = swp_pager_async_iodone;
1256 bio->bio_offset = (off_t)(blk - (reqpage - i)) << PAGE_SHIFT;
1257 bio->bio_driver_info = (void *)(reqpage - i);
1260 int k;
1262 for (k = i; k < j; ++k) {
1263 bp->b_xio.xio_pages[k - i] = m[k];
1264 vm_page_flag_set(m[k], PG_SWAPINPROG);
1267 bp->b_xio.xio_npages = j - i;
1269 mycpu->gd_cnt.v_swapin++;
1270 mycpu->gd_cnt.v_swappgsin += bp->b_xio.xio_npages;
1273 * We still hold the lock on mreq, and our automatic completion routine
1274 * does not remove it.
1277 vm_object_pip_add(mreq->object, bp->b_xio.xio_npages);
1278 lastpindex = m[j-1]->pindex;
1281 * perform the I/O. NOTE!!! bp cannot be considered valid after
1282 * this point because we automatically release it on completion.
1283 * Instead, we look at the one page we are interested in which we
1284 * still hold a lock on even through the I/O completion.
1286 * The other pages in our m[] array are also released on completion,
1287 * so we cannot assume they are valid anymore either.
1290 bp->b_cmd = BUF_CMD_READ;
1291 BUF_KERNPROC(bp);
1292 vn_strategy(swapdev_vp, bio);
1295 * wait for the page we want to complete. PG_SWAPINPROG is always
1296 * cleared on completion. If an I/O error occurs, SWAPBLK_NONE
1297 * is set in the meta-data.
1300 crit_enter();
1302 while ((mreq->flags & PG_SWAPINPROG) != 0) {
1303 vm_page_flag_set(mreq, PG_WANTED | PG_REFERENCED);
1304 mycpu->gd_cnt.v_intrans++;
1305 if (tsleep(mreq, 0, "swread", hz*20)) {
1306 kprintf(
1307 "swap_pager: indefinite wait buffer: "
1308 " offset: %lld, size: %d\n",
1309 bio->bio_offset, bp->b_bcount
1314 crit_exit();
1317 * mreq is left bussied after completion, but all the other pages
1318 * are freed. If we had an unrecoverable read error the page will
1319 * not be valid.
1322 if (mreq->valid != VM_PAGE_BITS_ALL) {
1323 return(VM_PAGER_ERROR);
1324 } else {
1325 return(VM_PAGER_OK);
1329 * A final note: in a low swap situation, we cannot deallocate swap
1330 * and mark a page dirty here because the caller is likely to mark
1331 * the page clean when we return, causing the page to possibly revert
1332 * to all-zero's later.
1337 * swap_pager_putpages:
1339 * Assign swap (if necessary) and initiate I/O on the specified pages.
1341 * We support both OBJT_DEFAULT and OBJT_SWAP objects. DEFAULT objects
1342 * are automatically converted to SWAP objects.
1344 * In a low memory situation we may block in vn_strategy(), but the new
1345 * vm_page reservation system coupled with properly written VFS devices
1346 * should ensure that no low-memory deadlock occurs. This is an area
1347 * which needs work.
1349 * The parent has N vm_object_pip_add() references prior to
1350 * calling us and will remove references for rtvals[] that are
1351 * not set to VM_PAGER_PEND. We need to remove the rest on I/O
1352 * completion.
1354 * The parent has soft-busy'd the pages it passes us and will unbusy
1355 * those whos rtvals[] entry is not set to VM_PAGER_PEND on return.
1356 * We need to unbusy the rest on I/O completion.
1358 void
1359 swap_pager_putpages(vm_object_t object, vm_page_t *m, int count,
1360 boolean_t sync, int *rtvals)
1362 int i;
1363 int n = 0;
1365 if (count && m[0]->object != object) {
1366 panic("swap_pager_getpages: object mismatch %p/%p",
1367 object,
1368 m[0]->object
1373 * Step 1
1375 * Turn object into OBJT_SWAP
1376 * check for bogus sysops
1377 * force sync if not pageout process
1380 if (object->type != OBJT_SWAP)
1381 swp_pager_meta_build(object, 0, SWAPBLK_NONE);
1383 if (curthread != pagethread)
1384 sync = TRUE;
1387 * Step 2
1389 * Update nsw parameters from swap_async_max sysctl values.
1390 * Do not let the sysop crash the machine with bogus numbers.
1393 if (swap_async_max != nsw_wcount_async_max) {
1394 int n;
1397 * limit range
1399 if ((n = swap_async_max) > nswbuf / 2)
1400 n = nswbuf / 2;
1401 if (n < 1)
1402 n = 1;
1403 swap_async_max = n;
1406 * Adjust difference ( if possible ). If the current async
1407 * count is too low, we may not be able to make the adjustment
1408 * at this time.
1410 crit_enter();
1411 n -= nsw_wcount_async_max;
1412 if (nsw_wcount_async + n >= 0) {
1413 nsw_wcount_async += n;
1414 nsw_wcount_async_max += n;
1415 wakeup(&nsw_wcount_async);
1417 crit_exit();
1421 * Step 3
1423 * Assign swap blocks and issue I/O. We reallocate swap on the fly.
1424 * The page is left dirty until the pageout operation completes
1425 * successfully.
1428 for (i = 0; i < count; i += n) {
1429 struct buf *bp;
1430 struct bio *bio;
1431 daddr_t blk;
1432 int j;
1435 * Maximum I/O size is limited by a number of factors.
1438 n = min(BLIST_MAX_ALLOC, count - i);
1439 n = min(n, nsw_cluster_max);
1441 crit_enter();
1444 * Get biggest block of swap we can. If we fail, fall
1445 * back and try to allocate a smaller block. Don't go
1446 * overboard trying to allocate space if it would overly
1447 * fragment swap.
1449 while (
1450 (blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE &&
1451 n > 4
1453 n >>= 1;
1455 if (blk == SWAPBLK_NONE) {
1456 for (j = 0; j < n; ++j)
1457 rtvals[i+j] = VM_PAGER_FAIL;
1458 crit_exit();
1459 continue;
1463 * The I/O we are constructing cannot cross a physical
1464 * disk boundry in the swap stripe. Note: we are still
1465 * at splvm().
1467 if ((blk ^ (blk + n)) & dmmax_mask) {
1468 j = ((blk + dmmax) & dmmax_mask) - blk;
1469 swp_pager_freeswapspace(blk + j, n - j);
1470 n = j;
1474 * All I/O parameters have been satisfied, build the I/O
1475 * request and assign the swap space.
1478 if (sync == TRUE)
1479 bp = getpbuf(&nsw_wcount_sync);
1480 else
1481 bp = getpbuf(&nsw_wcount_async);
1482 bio = &bp->b_bio1;
1484 pmap_qenter((vm_offset_t)bp->b_data, &m[i], n);
1486 bp->b_bcount = PAGE_SIZE * n;
1487 bio->bio_offset = (off_t)blk << PAGE_SHIFT;
1489 for (j = 0; j < n; ++j) {
1490 vm_page_t mreq = m[i+j];
1492 swp_pager_meta_build(
1493 mreq->object,
1494 mreq->pindex,
1495 blk + j
1497 vm_page_dirty(mreq);
1498 rtvals[i+j] = VM_PAGER_OK;
1500 vm_page_flag_set(mreq, PG_SWAPINPROG);
1501 bp->b_xio.xio_pages[j] = mreq;
1503 bp->b_xio.xio_npages = n;
1505 mycpu->gd_cnt.v_swapout++;
1506 mycpu->gd_cnt.v_swappgsout += bp->b_xio.xio_npages;
1508 crit_exit();
1510 bp->b_dirtyoff = 0; /* req'd for NFS */
1511 bp->b_dirtyend = bp->b_bcount; /* req'd for NFS */
1512 bp->b_cmd = BUF_CMD_WRITE;
1515 * asynchronous
1517 if (sync == FALSE) {
1518 bp->b_flags |= B_ASYNC;
1519 bio->bio_done = swp_pager_async_iodone;
1520 BUF_KERNPROC(bp);
1521 vn_strategy(swapdev_vp, bio);
1523 for (j = 0; j < n; ++j)
1524 rtvals[i+j] = VM_PAGER_PEND;
1525 continue;
1529 * synchronous
1532 bio->bio_done = swp_pager_sync_iodone;
1533 vn_strategy(swapdev_vp, bio);
1536 * Wait for the sync I/O to complete, then update rtvals.
1537 * We just set the rtvals[] to VM_PAGER_PEND so we can call
1538 * our async completion routine at the end, thus avoiding a
1539 * double-free.
1541 crit_enter();
1543 while (bp->b_cmd != BUF_CMD_DONE)
1544 tsleep(bp, 0, "swwrt", 0);
1546 for (j = 0; j < n; ++j)
1547 rtvals[i+j] = VM_PAGER_PEND;
1550 * Now that we are through with the bp, we can call the
1551 * normal async completion, which frees everything up.
1554 swp_pager_async_iodone(bio);
1556 crit_exit();
1560 void
1561 swap_pager_newswap(void)
1563 swp_sizecheck();
1567 * swap_pager_sync_iodone:
1569 * Completion routine for synchronous reads and writes from/to swap.
1570 * We just mark the bp is complete and wake up anyone waiting on it.
1572 * This routine may not block. This routine is called at splbio()
1573 * or better.
1576 static void
1577 swp_pager_sync_iodone(struct bio *bio)
1579 struct buf *bp = bio->bio_buf;
1581 bp->b_flags &= ~B_ASYNC;
1582 bp->b_cmd = BUF_CMD_DONE;
1583 wakeup(bp);
1587 * swp_pager_async_iodone:
1589 * Completion routine for asynchronous reads and writes from/to swap.
1590 * Also called manually by synchronous code to finish up a bp.
1592 * For READ operations, the pages are PG_BUSY'd. For WRITE operations,
1593 * the pages are vm_page_t->busy'd. For READ operations, we PG_BUSY
1594 * unbusy all pages except the 'main' request page. For WRITE
1595 * operations, we vm_page_t->busy'd unbusy all pages ( we can do this
1596 * because we marked them all VM_PAGER_PEND on return from putpages ).
1598 * This routine may not block.
1601 static void
1602 swp_pager_async_iodone(struct bio *bio)
1604 struct buf *bp = bio->bio_buf;
1605 vm_object_t object = NULL;
1606 int i;
1607 int *nswptr;
1610 * report error
1612 if (bp->b_flags & B_ERROR) {
1613 kprintf(
1614 "swap_pager: I/O error - %s failed; offset %lld,"
1615 "size %ld, error %d\n",
1616 ((bp->b_cmd == BUF_CMD_READ) ? "pagein" : "pageout"),
1617 bio->bio_offset,
1618 (long)bp->b_bcount,
1619 bp->b_error
1624 * set object, raise to splvm().
1627 if (bp->b_xio.xio_npages)
1628 object = bp->b_xio.xio_pages[0]->object;
1629 crit_enter();
1632 * remove the mapping for kernel virtual
1635 pmap_qremove((vm_offset_t)bp->b_data, bp->b_xio.xio_npages);
1638 * cleanup pages. If an error occurs writing to swap, we are in
1639 * very serious trouble. If it happens to be a disk error, though,
1640 * we may be able to recover by reassigning the swap later on. So
1641 * in this case we remove the m->swapblk assignment for the page
1642 * but do not free it in the rlist. The errornous block(s) are thus
1643 * never reallocated as swap. Redirty the page and continue.
1646 for (i = 0; i < bp->b_xio.xio_npages; ++i) {
1647 vm_page_t m = bp->b_xio.xio_pages[i];
1649 vm_page_flag_clear(m, PG_SWAPINPROG);
1651 if (bp->b_flags & B_ERROR) {
1653 * If an error occurs I'd love to throw the swapblk
1654 * away without freeing it back to swapspace, so it
1655 * can never be used again. But I can't from an
1656 * interrupt.
1659 if (bp->b_cmd == BUF_CMD_READ) {
1661 * When reading, reqpage needs to stay
1662 * locked for the parent, but all other
1663 * pages can be freed. We still want to
1664 * wakeup the parent waiting on the page,
1665 * though. ( also: pg_reqpage can be -1 and
1666 * not match anything ).
1668 * We have to wake specifically requested pages
1669 * up too because we cleared PG_SWAPINPROG and
1670 * someone may be waiting for that.
1672 * NOTE: for reads, m->dirty will probably
1673 * be overridden by the original caller of
1674 * getpages so don't play cute tricks here.
1676 * NOTE: We can't actually free the page from
1677 * here, because this is an interrupt. It
1678 * is not legal to mess with object->memq
1679 * from an interrupt. Deactivate the page
1680 * instead.
1683 m->valid = 0;
1684 vm_page_flag_clear(m, PG_ZERO);
1687 * bio_driver_info holds the requested page
1688 * index.
1690 if (i != (int)bio->bio_driver_info) {
1691 vm_page_deactivate(m);
1692 vm_page_wakeup(m);
1693 } else {
1694 vm_page_flash(m);
1697 * If i == bp->b_pager.pg_reqpage, do not wake
1698 * the page up. The caller needs to.
1700 } else {
1702 * If a write error occurs, reactivate page
1703 * so it doesn't clog the inactive list,
1704 * then finish the I/O.
1706 vm_page_dirty(m);
1707 kprintf("f");
1708 vm_page_activate(m);
1709 vm_page_io_finish(m);
1711 } else if (bp->b_cmd == BUF_CMD_READ) {
1713 * NOTE: for reads, m->dirty will probably be
1714 * overridden by the original caller of getpages so
1715 * we cannot set them in order to free the underlying
1716 * swap in a low-swap situation. I don't think we'd
1717 * want to do that anyway, but it was an optimization
1718 * that existed in the old swapper for a time before
1719 * it got ripped out due to precisely this problem.
1721 * clear PG_ZERO in page.
1723 * If not the requested page then deactivate it.
1725 * Note that the requested page, reqpage, is left
1726 * busied, but we still have to wake it up. The
1727 * other pages are released (unbusied) by
1728 * vm_page_wakeup(). We do not set reqpage's
1729 * valid bits here, it is up to the caller.
1733 * NOTE: can't call pmap_clear_modify(m) from an
1734 * interrupt thread, the pmap code may have to map
1735 * non-kernel pmaps and currently asserts the case.
1737 /*pmap_clear_modify(m);*/
1738 m->valid = VM_PAGE_BITS_ALL;
1739 vm_page_undirty(m);
1740 vm_page_flag_clear(m, PG_ZERO);
1743 * We have to wake specifically requested pages
1744 * up too because we cleared PG_SWAPINPROG and
1745 * could be waiting for it in getpages. However,
1746 * be sure to not unbusy getpages specifically
1747 * requested page - getpages expects it to be
1748 * left busy.
1750 * bio_driver_info holds the requested page
1752 if (i != (int)bio->bio_driver_info) {
1753 vm_page_deactivate(m);
1754 vm_page_wakeup(m);
1755 } else {
1756 vm_page_flash(m);
1758 } else {
1760 * Mark the page clean but do not mess with the
1761 * pmap-layer's modified state. That state should
1762 * also be clear since the caller protected the
1763 * page VM_PROT_READ, but allow the case.
1765 * We are in an interrupt, avoid pmap operations.
1767 * If we have a severe page deficit, deactivate the
1768 * page. Do not try to cache it (which would also
1769 * involve a pmap op), because the page might still
1770 * be read-heavy.
1772 vm_page_undirty(m);
1773 vm_page_io_finish(m);
1774 if (vm_page_count_severe())
1775 vm_page_deactivate(m);
1776 #if 0
1777 if (!vm_page_count_severe() || !vm_page_try_to_cache(m))
1778 vm_page_protect(m, VM_PROT_READ);
1779 #endif
1784 * adjust pip. NOTE: the original parent may still have its own
1785 * pip refs on the object.
1788 if (object)
1789 vm_object_pip_wakeupn(object, bp->b_xio.xio_npages);
1792 * release the physical I/O buffer
1794 if (bp->b_cmd == BUF_CMD_READ)
1795 nswptr = &nsw_rcount;
1796 else if (bp->b_flags & B_ASYNC)
1797 nswptr = &nsw_wcount_async;
1798 else
1799 nswptr = &nsw_wcount_sync;
1800 bp->b_cmd = BUF_CMD_DONE;
1801 relpbuf(bp, nswptr);
1802 crit_exit();
1805 /************************************************************************
1806 * SWAP META DATA *
1807 ************************************************************************
1809 * These routines manipulate the swap metadata stored in the
1810 * OBJT_SWAP object. All swp_*() routines must be called at
1811 * splvm() because swap can be freed up by the low level vm_page
1812 * code which might be called from interrupts beyond what splbio() covers.
1814 * Swap metadata is implemented with a global hash and not directly
1815 * linked into the object. Instead the object simply contains
1816 * appropriate tracking counters.
1820 * SWP_PAGER_HASH() - hash swap meta data
1822 * This is an inline helper function which hashes the swapblk given
1823 * the object and page index. It returns a pointer to a pointer
1824 * to the object, or a pointer to a NULL pointer if it could not
1825 * find a swapblk.
1827 * This routine must be called at splvm().
1830 static __inline struct swblock **
1831 swp_pager_hash(vm_object_t object, vm_pindex_t index)
1833 struct swblock **pswap;
1834 struct swblock *swap;
1836 index &= ~SWAP_META_MASK;
1837 pswap = &swhash[(index ^ (int)(intptr_t)object) & swhash_mask];
1839 while ((swap = *pswap) != NULL) {
1840 if (swap->swb_object == object &&
1841 swap->swb_index == index
1843 break;
1845 pswap = &swap->swb_hnext;
1847 return(pswap);
1851 * SWP_PAGER_META_BUILD() - add swap block to swap meta data for object
1853 * We first convert the object to a swap object if it is a default
1854 * object.
1856 * The specified swapblk is added to the object's swap metadata. If
1857 * the swapblk is not valid, it is freed instead. Any previously
1858 * assigned swapblk is freed.
1860 * This routine must be called at splvm(), except when used to convert
1861 * an OBJT_DEFAULT object into an OBJT_SWAP object.
1865 static void
1866 swp_pager_meta_build(
1867 vm_object_t object,
1868 vm_pindex_t index,
1869 daddr_t swapblk
1871 struct swblock *swap;
1872 struct swblock **pswap;
1875 * Convert default object to swap object if necessary
1878 if (object->type != OBJT_SWAP) {
1879 object->type = OBJT_SWAP;
1880 object->un_pager.swp.swp_bcount = 0;
1882 if (object->handle != NULL) {
1883 TAILQ_INSERT_TAIL(
1884 NOBJLIST(object->handle),
1885 object,
1886 pager_object_list
1888 } else {
1889 TAILQ_INSERT_TAIL(
1890 &swap_pager_un_object_list,
1891 object,
1892 pager_object_list
1898 * Locate hash entry. If not found create, but if we aren't adding
1899 * anything just return. If we run out of space in the map we wait
1900 * and, since the hash table may have changed, retry.
1903 retry:
1904 pswap = swp_pager_hash(object, index);
1906 if ((swap = *pswap) == NULL) {
1907 int i;
1909 if (swapblk == SWAPBLK_NONE)
1910 return;
1912 swap = *pswap = zalloc(swap_zone);
1913 if (swap == NULL) {
1914 vm_wait(0);
1915 goto retry;
1917 swap->swb_hnext = NULL;
1918 swap->swb_object = object;
1919 swap->swb_index = index & ~SWAP_META_MASK;
1920 swap->swb_count = 0;
1922 ++object->un_pager.swp.swp_bcount;
1924 for (i = 0; i < SWAP_META_PAGES; ++i)
1925 swap->swb_pages[i] = SWAPBLK_NONE;
1929 * Delete prior contents of metadata
1932 index &= SWAP_META_MASK;
1934 if (swap->swb_pages[index] != SWAPBLK_NONE) {
1935 swp_pager_freeswapspace(swap->swb_pages[index], 1);
1936 --swap->swb_count;
1940 * Enter block into metadata
1943 swap->swb_pages[index] = swapblk;
1944 if (swapblk != SWAPBLK_NONE)
1945 ++swap->swb_count;
1949 * SWP_PAGER_META_FREE() - free a range of blocks in the object's swap metadata
1951 * The requested range of blocks is freed, with any associated swap
1952 * returned to the swap bitmap.
1954 * This routine will free swap metadata structures as they are cleaned
1955 * out. This routine does *NOT* operate on swap metadata associated
1956 * with resident pages.
1958 * This routine must be called at splvm()
1961 static void
1962 swp_pager_meta_free(vm_object_t object, vm_pindex_t index, daddr_t count)
1964 if (object->type != OBJT_SWAP)
1965 return;
1967 while (count > 0) {
1968 struct swblock **pswap;
1969 struct swblock *swap;
1971 pswap = swp_pager_hash(object, index);
1973 if ((swap = *pswap) != NULL) {
1974 daddr_t v = swap->swb_pages[index & SWAP_META_MASK];
1976 if (v != SWAPBLK_NONE) {
1977 swp_pager_freeswapspace(v, 1);
1978 swap->swb_pages[index & SWAP_META_MASK] =
1979 SWAPBLK_NONE;
1980 if (--swap->swb_count == 0) {
1981 *pswap = swap->swb_hnext;
1982 zfree(swap_zone, swap);
1983 --object->un_pager.swp.swp_bcount;
1986 --count;
1987 ++index;
1988 } else {
1989 int n = SWAP_META_PAGES - (index & SWAP_META_MASK);
1990 count -= n;
1991 index += n;
1997 * SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object
1999 * This routine locates and destroys all swap metadata associated with
2000 * an object.
2002 * This routine must be called at splvm()
2005 static void
2006 swp_pager_meta_free_all(vm_object_t object)
2008 daddr_t index = 0;
2010 if (object->type != OBJT_SWAP)
2011 return;
2013 while (object->un_pager.swp.swp_bcount) {
2014 struct swblock **pswap;
2015 struct swblock *swap;
2017 pswap = swp_pager_hash(object, index);
2018 if ((swap = *pswap) != NULL) {
2019 int i;
2021 for (i = 0; i < SWAP_META_PAGES; ++i) {
2022 daddr_t v = swap->swb_pages[i];
2023 if (v != SWAPBLK_NONE) {
2024 --swap->swb_count;
2025 swp_pager_freeswapspace(v, 1);
2028 if (swap->swb_count != 0)
2029 panic("swap_pager_meta_free_all: swb_count != 0");
2030 *pswap = swap->swb_hnext;
2031 zfree(swap_zone, swap);
2032 --object->un_pager.swp.swp_bcount;
2034 index += SWAP_META_PAGES;
2035 if (index > 0x20000000)
2036 panic("swp_pager_meta_free_all: failed to locate all swap meta blocks");
2041 * SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data.
2043 * This routine is capable of looking up, popping, or freeing
2044 * swapblk assignments in the swap meta data or in the vm_page_t.
2045 * The routine typically returns the swapblk being looked-up, or popped,
2046 * or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block
2047 * was invalid. This routine will automatically free any invalid
2048 * meta-data swapblks.
2050 * It is not possible to store invalid swapblks in the swap meta data
2051 * (other then a literal 'SWAPBLK_NONE'), so we don't bother checking.
2053 * When acting on a busy resident page and paging is in progress, we
2054 * have to wait until paging is complete but otherwise can act on the
2055 * busy page.
2057 * This routine must be called at splvm().
2059 * SWM_FREE remove and free swap block from metadata
2060 * SWM_POP remove from meta data but do not free.. pop it out
2063 static daddr_t
2064 swp_pager_meta_ctl(
2065 vm_object_t object,
2066 vm_pindex_t index,
2067 int flags
2069 struct swblock **pswap;
2070 struct swblock *swap;
2071 daddr_t r1;
2074 * The meta data only exists of the object is OBJT_SWAP
2075 * and even then might not be allocated yet.
2078 if (object->type != OBJT_SWAP)
2079 return(SWAPBLK_NONE);
2081 r1 = SWAPBLK_NONE;
2082 pswap = swp_pager_hash(object, index);
2084 if ((swap = *pswap) != NULL) {
2085 index &= SWAP_META_MASK;
2086 r1 = swap->swb_pages[index];
2088 if (r1 != SWAPBLK_NONE) {
2089 if (flags & SWM_FREE) {
2090 swp_pager_freeswapspace(r1, 1);
2091 r1 = SWAPBLK_NONE;
2093 if (flags & (SWM_FREE|SWM_POP)) {
2094 swap->swb_pages[index] = SWAPBLK_NONE;
2095 if (--swap->swb_count == 0) {
2096 *pswap = swap->swb_hnext;
2097 zfree(swap_zone, swap);
2098 --object->un_pager.swp.swp_bcount;
2103 return(r1);