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freebsd-nq/sys/vm/swap_pager.c

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/*
* Copyright (c) 1998 Matthew Dillon,
* Copyright (c) 1994 John S. Dyson
* Copyright (c) 1990 University of Utah.
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* the Systems Programming Group of the University of Utah Computer
* Science Department.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* New Swap System
* Matthew Dillon
*
* Radix Bitmap 'blists'.
*
* - The new swapper uses the new radix bitmap code. This should scale
* to arbitrarily small or arbitrarily large swap spaces and an almost
* arbitrary degree of fragmentation.
*
* Features:
*
* - on the fly reallocation of swap during putpages. The new system
* does not try to keep previously allocated swap blocks for dirty
* pages.
*
* - on the fly deallocation of swap
*
* - No more garbage collection required. Unnecessarily allocated swap
* blocks only exist for dirty vm_page_t's now and these are already
* cycled (in a high-load system) by the pager. We also do on-the-fly
* removal of invalidated swap blocks when a page is destroyed
* or renamed.
*
* from: Utah $Hdr: swap_pager.c 1.4 91/04/30$
*
* @(#)swap_pager.c 8.9 (Berkeley) 3/21/94
*
* $Id: swap_pager.c,v 1.111 1999/01/24 06:04:51 dillon Exp $
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/vmmeter.h>
#include <sys/blist.h>
#include <sys/lock.h>
#ifndef MAX_PAGEOUT_CLUSTER
#define MAX_PAGEOUT_CLUSTER 16
#endif
#define SWB_NPAGES MAX_PAGEOUT_CLUSTER
#include "opt_swap.h"
#include <vm/vm.h>
#include <vm/vm_prot.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vm_pageout.h>
#include <vm/swap_pager.h>
#include <vm/vm_extern.h>
#include <vm/vm_zone.h>
#define SWM_FREE 0x02 /* free, period */
#define SWM_POP 0x04 /* pop out */
/*
* vm_swap_size is in page-sized chunks now. It was DEV_BSIZE'd chunks
* in the old system.
*/
extern int vm_swap_size; /* number of free swap blocks, in pages */
int swap_pager_full; /* swap space exhaustion (w/ hysteresis)*/
static int nsw_rcount; /* free read buffers */
static int nsw_wcount; /* free write buffers */
static int nsw_hysteresis; /* hysteresis */
static int max_pageout_cluster; /* maximum VOP I/O allowed */
static int sw_alloc_interlock; /* swap pager allocation interlock */
struct blist *swapblist;
static struct swblock **swhash;
static int swhash_mask;
/*
* "named" and "unnamed" anon region objects. Try to reduce the overhead
* of searching a named list by hashing it just a little.
*/
#define NOBJLISTS 8
#define NOBJLIST(handle) \
(&swap_pager_object_list[((int)(long)handle >> 4) & (NOBJLISTS-1)])
static struct pagerlst swap_pager_object_list[NOBJLISTS];
struct pagerlst swap_pager_un_object_list;
vm_zone_t swap_zone;
/*
* pagerops for OBJT_SWAP - "swap pager". Some ops are also global procedure
* calls hooked from other parts of the VM system and do not appear here.
* (see vm/swap_pager.h).
*/
static vm_object_t
swap_pager_alloc __P((void *handle, vm_ooffset_t size,
vm_prot_t prot, vm_ooffset_t offset));
static void swap_pager_dealloc __P((vm_object_t object));
static int swap_pager_getpages __P((vm_object_t, vm_page_t *, int, int));
static void swap_pager_init __P((void));
static void swap_pager_unswapped __P((vm_page_t));
struct pagerops swappagerops = {
swap_pager_init, /* early system initialization of pager */
swap_pager_alloc, /* allocate an OBJT_SWAP object */
swap_pager_dealloc, /* deallocate an OBJT_SWAP object */
swap_pager_getpages, /* pagein */
swap_pager_putpages, /* pageout */
swap_pager_haspage, /* get backing store status for page */
swap_pager_unswapped /* remove swap related to page */
};
/*
* dmmax is in page-sized chunks with the new swap system. It was
* dev-bsized chunks in the old.
*
* swap_*() routines are externally accessible. swp_*() routines are
* internal.
*/
int dmmax;
static int dmmax_mask;
int nswap_lowat = 128; /* in pages, swap_pager_full warning */
int nswap_hiwat = 256; /* in pages, swap_pager_full warning */
static __inline void swp_sizecheck __P((void));
static void swp_pager_sync_iodone __P((struct buf *bp));
static void swp_pager_async_iodone __P((struct buf *bp));
/*
* Swap bitmap functions
*/
static __inline void swp_pager_freeswapspace __P((daddr_t blk, int npages));
static __inline daddr_t swp_pager_getswapspace __P((int npages));
/*
* Metadata functions
*/
static void swp_pager_meta_build __P((vm_object_t, daddr_t, daddr_t, int));
static void swp_pager_meta_free __P((vm_object_t, daddr_t, daddr_t));
static void swp_pager_meta_free_all __P((vm_object_t));
static daddr_t swp_pager_meta_ctl __P((vm_object_t, vm_pindex_t, int));
/*
* SWP_SIZECHECK() - update swap_pager_full indication
*
* update the swap_pager_full indication and warn when we are
* about to run out of swap space.
*
* No restrictions on call
* This routine may not block.
* This routine must be called at splvm()
*/
static __inline void
swp_sizecheck()
{
if (vm_swap_size < nswap_lowat) {
if (swap_pager_full == 0)
printf("swap_pager: out of swap space\n");
swap_pager_full = 1;
} else if (vm_swap_size > nswap_hiwat) {
swap_pager_full = 0;
}
}
/*
* SWAP_PAGER_INIT() - initialize the swap pager!
*
* Expected to be started from system init. NOTE: This code is run
* before much else so be careful what you depend on. Most of the VM
* system has yet to be initialized at this point.
*/
static void
swap_pager_init()
{
/*
* Initialize object lists
*/
int i;
for (i = 0; i < NOBJLISTS; ++i)
TAILQ_INIT(&swap_pager_object_list[i]);
TAILQ_INIT(&swap_pager_un_object_list);
/*
* Device Stripe, in PAGE_SIZE'd blocks
*/
dmmax = SWB_NPAGES * 2;
dmmax_mask = ~(dmmax - 1);
}
/*
* SWAP_PAGER_SWAP_INIT() - swap pager initialization from pageout process
*
* Expected to be started from pageout process once, prior to entering
* its main loop.
*/
void
swap_pager_swap_init()
{
int n;
/*
* Number of in-transit swap bp operations. Don't
* exhaust the pbufs completely. Make sure we
* initialize workable values (0 will work for hysteresis
* but it isn't very efficient).
*
* The max_pageout_cluster is constrained by the bp->b_pages[]
* array (MAXPHYS/PAGE_SIZE) and our locally defined
* MAX_PAGEOUT_CLUSTER. Also be aware that swap ops are
* constrained by the swap device interleave stripe size.
*/
nsw_rcount = (nswbuf + 1) / 2;
nsw_wcount = (nswbuf + 3) / 4;
nsw_hysteresis = nsw_wcount / 2;
max_pageout_cluster = min((MAXPHYS/PAGE_SIZE), MAX_PAGEOUT_CLUSTER);
/*
* Initialize our zone. Right now I'm just guessing on the number
* we need based on the number of pages in the system. Each swblock
* can hold 16 pages, so this is probably overkill.
*/
n = cnt.v_page_count * 2;
swap_zone = zinit(
"SWAPMETA",
sizeof(struct swblock),
n,
ZONE_INTERRUPT,
1
);
/*
* Initialize our meta-data hash table. The swapper does not need to
* be quite as efficient as the VM system, so we do not use an
* oversized hash table.
*
* n: size of hash table, must be power of 2
* swhash_mask: hash table index mask
*/
for (n = 1; n < cnt.v_page_count / 4; n <<= 1)
;
swhash = malloc(sizeof(struct swblock *) * n, M_VMPGDATA, M_WAITOK);
bzero(swhash, sizeof(struct swblock *) * n);
swhash_mask = n - 1;
}
/*
* SWAP_PAGER_ALLOC() - allocate a new OBJT_SWAP VM object and instantiate
* its metadata structures.
*
* This routine is called from the mmap and fork code to create a new
* OBJT_SWAP object. We do this by creating an OBJT_DEFAULT object
* and then converting it with swp_pager_meta_build().
*
* This routine may block in vm_object_allocate() and create a named
* object lookup race, so we must interlock. We must also run at
* splvm() for the object lookup to handle races with interrupts, but
* we do not have to maintain splvm() in between the lookup and the
* add because (I believe) it is not possible to attempt to create
* a new swap object w/handle when a default object with that handle
* already exists.
*/
static vm_object_t
swap_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
vm_ooffset_t offset)
{
vm_object_t object;
if (handle) {
/*
* Reference existing named region or allocate new one. There
* should not be a race here against swp_pager_meta_build()
* as called from vm_page_remove() in regards to the lookup
* of the handle.
*/
while (sw_alloc_interlock) {
sw_alloc_interlock = -1;
tsleep(&sw_alloc_interlock, PVM, "swpalc", 0);
}
sw_alloc_interlock = 1;
object = vm_pager_object_lookup(NOBJLIST(handle), handle);
if (object != NULL) {
vm_object_reference(object);
} else {
object = vm_object_allocate(OBJT_DEFAULT,
OFF_TO_IDX(offset + PAGE_MASK + size));
object->handle = handle;
swp_pager_meta_build(
object,
0,
SWAPBLK_NONE,
0
);
}
if (sw_alloc_interlock < 0)
wakeup(&sw_alloc_interlock);
sw_alloc_interlock = 0;
} else {
object = vm_object_allocate(OBJT_DEFAULT,
OFF_TO_IDX(offset + PAGE_MASK + size));
swp_pager_meta_build(
object,
0,
SWAPBLK_NONE,
0
);
}
return (object);
}
/*
* SWAP_PAGER_DEALLOC() - remove swap metadata from object
*
* The swap backing for the object is destroyed. The code is
* designed such that we can reinstantiate it later, but this
* routine is typically called only when the entire object is
* about to be destroyed.
*
* This routine may block, but no longer does.
*
* The object must be locked or unreferenceable.
*/
static void
swap_pager_dealloc(object)
vm_object_t object;
{
/*
* Remove from list right away so lookups will fail if we block for
* pageout completion.
*/
if (object->handle == NULL) {
TAILQ_REMOVE(&swap_pager_un_object_list, object, pager_object_list);
} else {
TAILQ_REMOVE(NOBJLIST(object->handle), object, pager_object_list);
}
vm_object_pip_wait(object, "swpdea");
/*
* Free all remaining metadata. We only bother to free it from
* the swap meta data. We do not attempt to free swapblk's still
* associated with vm_page_t's for this object. We do not care
* if paging is still in progress on some objects.
*/
swp_pager_meta_free_all(object);
}
/************************************************************************
* SWAP PAGER BITMAP ROUTINES *
************************************************************************/
/*
* SWP_PAGER_GETSWAPSPACE() - allocate raw swap space
*
* Allocate swap for the requested number of pages. The starting
* swap block number (a page index) is returned or SWAPBLK_NONE
* if the allocation failed.
*
* Also has the side effect of advising that somebody made a mistake
* when they configured swap and didn't configure enough.
*
* Must be called at splvm() to avoid races with bitmap frees from
* vm_page_remove() aka swap_pager_page_removed().
*
* This routine may not block
* This routine must be called at splvm().
*/
static __inline daddr_t
swp_pager_getswapspace(npages)
int npages;
{
daddr_t blk;
if ((blk = blist_alloc(swapblist, npages)) == SWAPBLK_NONE) {
printf("swap_pager_getswapspace: failed\n");
} else {
vm_swap_size -= npages;
swp_sizecheck();
}
return(blk);
}
/*
* SWP_PAGER_FREESWAPSPACE() - free raw swap space
*
* This routine returns the specified swap blocks back to the bitmap.
*
* Note: This routine may not block (it could in the old swap code),
* and through the use of the new blist routines it does not block.
*
* We must be called at splvm() to avoid races with bitmap frees from
* vm_page_remove() aka swap_pager_page_removed().
*
* This routine may not block
* This routine must be called at splvm().
*/
static __inline void
swp_pager_freeswapspace(blk, npages)
daddr_t blk;
int npages;
{
blist_free(swapblist, blk, npages);
vm_swap_size += npages;
swp_sizecheck();
}
/*
* SWAP_PAGER_FREESPACE() - frees swap blocks associated with a page
* range within an object.
*
* This is a globally accessible routine.
*
* This routine removes swapblk assignments from swap metadata.
*
* The external callers of this routine typically have already destroyed
* or renamed vm_page_t's associated with this range in the object so
* we should be ok.
*/
void
swap_pager_freespace(object, start, size)
vm_object_t object;
vm_pindex_t start;
vm_size_t size;
{
swp_pager_meta_free(object, start, size);
}
/*
* SWAP_PAGER_COPY() - copy blocks from source pager to destination pager
* and destroy the source.
*
* Copy any valid swapblks from the source to the destination. In
* cases where both the source and destination have a valid swapblk,
* we keep the destination's.
*
* This routine is allowed to block. It may block allocating metadata
* indirectly through swp_pager_meta_build() or if paging is still in
* progress on the source.
*
* XXX vm_page_collapse() kinda expects us not to block because we
* supposedly do not need to allocate memory, but for the moment we
* *may* have to get a little memory from the zone allocator, but
* it is taken from the interrupt memory. We should be ok.
*
* The source object contains no vm_page_t's (which is just as well)
*
* The source object is of type OBJT_SWAP.
*
* The source and destination objects must be
* locked or inaccessible (XXX are they ?)
*/
void
swap_pager_copy(srcobject, dstobject, offset, destroysource)
vm_object_t srcobject;
vm_object_t dstobject;
vm_pindex_t offset;
int destroysource;
{
vm_pindex_t i;
/*
* If destroysource is set, we remove the source object from the
* swap_pager internal queue now.
*/
if (destroysource) {
if (srcobject->handle == NULL) {
TAILQ_REMOVE(
&swap_pager_un_object_list,
srcobject,
pager_object_list
);
} else {
TAILQ_REMOVE(
NOBJLIST(srcobject->handle),
srcobject,
pager_object_list
);
}
}
/*
* transfer source to destination.
*/
for (i = 0; i < dstobject->size; ++i) {
daddr_t dstaddr;
/*
* Locate (without changing) the swapblk on the destination,
* unless it is invalid in which case free it silently, or
* if the destination is a resident page, in which case the
* source is thrown away.
*/
dstaddr = swp_pager_meta_ctl(dstobject, i, 0);
if (dstaddr == SWAPBLK_NONE) {
/*
* Destination has no swapblk and is not resident,
* copy source.
*/
daddr_t srcaddr;
srcaddr = swp_pager_meta_ctl(
srcobject,
i + offset,
SWM_POP
);
if (srcaddr != SWAPBLK_NONE)
swp_pager_meta_build(dstobject, i, srcaddr, 1);
} else {
/*
* Destination has valid swapblk or it is represented
* by a resident page. We destroy the sourceblock.
*/
swp_pager_meta_ctl(srcobject, i + offset, SWM_FREE);
}
}
/*
* Free left over swap blocks in source.
*
* We have to revert the type to OBJT_DEFAULT so we do not accidently
* double-remove the object from the swap queues.
*/
if (destroysource) {
swp_pager_meta_free_all(srcobject);
/*
* Reverting the type is not necessary, the caller is going
* to destroy srcobject directly, but I'm doing it here
* for consistancy since we've removed the object from its
* queues.
*/
srcobject->type = OBJT_DEFAULT;
}
return;
}
/*
* SWAP_PAGER_HASPAGE() - determine if we have good backing store for
* the requested page.
*
* We determine whether good backing store exists for the requested
* page and return TRUE if it does, FALSE if it doesn't.
*
* If TRUE, we also try to determine how much valid, contiguous backing
* store exists before and after the requested page within a reasonable
* distance. We do not try to restrict it to the swap device stripe
* (that is handled in getpages/putpages). It probably isn't worth
* doing here.
*/
boolean_t
swap_pager_haspage(object, pindex, before, after)
vm_object_t object;
vm_pindex_t pindex;
int *before;
int *after;
{
daddr_t blk0;
/*
* do we have good backing store at the requested index ?
*/
blk0 = swp_pager_meta_ctl(object, pindex, 0);
if (blk0 & SWAPBLK_NONE) {
if (before)
*before = 0;
if (after)
*after = 0;
return (FALSE);
}
/*
* find backwards-looking contiguous good backing store
*/
if (before != NULL) {
int i;
for (i = 1; i < (SWB_NPAGES/2); ++i) {
daddr_t blk;
if (i > pindex)
break;
blk = swp_pager_meta_ctl(object, pindex - i, 0);
if (blk & SWAPBLK_NONE)
break;
if (blk != blk0 - i)
break;
}
*before = (i - 1);
}
/*
* find forward-looking contiguous good backing store
*/
if (after != NULL) {
int i;
for (i = 1; i < (SWB_NPAGES/2); ++i) {
daddr_t blk;
blk = swp_pager_meta_ctl(object, pindex + i, 0);
if (blk & SWAPBLK_NONE)
break;
if (blk != blk0 + i)
break;
}
*after = (i - 1);
}
return (TRUE);
}
/*
* SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page
*
* This removes any associated swap backing store, whether valid or
* not, from the page.
*
* This routine is typically called when a page is made dirty, at
* which point any associated swap can be freed. MADV_FREE also
* calls us in a special-case situation
*
* NOTE!!! If the page is clean and the swap was valid, the caller
* should make the page dirty before calling this routine. This routine
* does NOT change the m->dirty status of the page. Also: MADV_FREE
* depends on it.
*
* This routine may not block
*/
static void
swap_pager_unswapped(m)
vm_page_t m;
{
swp_pager_meta_ctl(m->object, m->pindex, SWM_FREE);
}
/*
* SWAP_PAGER_GETPAGES() - bring pages in from swap
*
* Attempt to retrieve (m, count) pages from backing store, but make
* sure we retrieve at least m[reqpage]. We try to load in as large
* a chunk surrounding m[reqpage] as is contiguous in swap and which
* belongs to the same object.
*
* The code is designed for asynchronous operation and
* immediate-notification of 'reqpage' but tends not to be
* used that way. Please do not optimize-out this algorithmic
* feature, I intend to improve on it in the future.
*
* The parent has a single vm_object_pip_add() reference prior to
* calling us and we should return with the same.
*
* The parent has BUSY'd the pages. We should return with 'm'
* left busy, but the others adjusted.
*/
static int
swap_pager_getpages(object, m, count, reqpage)
vm_object_t object;
vm_page_t *m;
int count, reqpage;
{
struct buf *bp;
vm_page_t mreq;
int s;
int i;
int j;
daddr_t blk;
vm_offset_t kva;
vm_pindex_t lastpindex;
mreq = m[reqpage];
#if !defined(MAX_PERF)
if (mreq->object != object) {
panic("swap_pager_getpages: object mismatch %p/%p",
object,
mreq->object
);
}
#endif
/*
* Calculate range to retrieve. The pages have already been assigned
* their swapblks. We require a *contiguous* range that falls entirely
* within a single device stripe. If we do not supply it, bad things
* happen.
*/
blk = swp_pager_meta_ctl(mreq->object, mreq->pindex, 0);
for (i = reqpage - 1; i >= 0; --i) {
daddr_t iblk;
iblk = swp_pager_meta_ctl(m[i]->object, m[i]->pindex, 0);
if (iblk & SWAPBLK_NONE)
break;
if ((blk ^ iblk) & dmmax_mask)
break;
if (blk != iblk + (reqpage - i))
break;
}
++i;
for (j = reqpage + 1; j < count; ++j) {
daddr_t jblk;
jblk = swp_pager_meta_ctl(m[j]->object, m[j]->pindex, 0);
if (jblk & SWAPBLK_NONE)
break;
if ((blk ^ jblk) & dmmax_mask)
break;
if (blk != jblk - (j - reqpage))
break;
}
/*
* If blk itself is bad, well, we can't do any I/O. This should
* already be covered as a side effect, but I'm making sure.
*/
if (blk & SWAPBLK_NONE) {
i = reqpage;
j = reqpage + 1;
}
/*
* free pages outside our collection range. Note: we never free
* mreq, it must remain busy throughout.
*/
{
int k;
for (k = 0; k < i; ++k) {
vm_page_free(m[k]);
}
for (k = j; k < count; ++k) {
vm_page_free(m[k]);
}
}
/*
* Return VM_PAGER_FAIL if we have nothing
* to do. Return mreq still busy, but the
* others unbusied.
*/
if (blk & SWAPBLK_NONE)
return(VM_PAGER_FAIL);
/*
* Get a swap buffer header to perform the IO
*/
bp = getpbuf(&nsw_rcount);
kva = (vm_offset_t) bp->b_data;
/*
* map our page(s) into kva for input
*
* NOTE: B_PAGING is set by pbgetvp()
*/
pmap_qenter(kva, m + i, j - i);
bp->b_flags = B_BUSY | B_READ | B_CALL;
bp->b_iodone = swp_pager_async_iodone;
bp->b_proc = &proc0; /* XXX (but without B_PHYS set this is ok) */
bp->b_rcred = bp->b_wcred = bp->b_proc->p_ucred;
crhold(bp->b_rcred);
crhold(bp->b_wcred);
bp->b_data = (caddr_t) kva;
/*
* b_blkno is in page-sized chunks. swapblk is valid, too, so
* we don't have to mask it against SWAPBLK_MASK.
*/
bp->b_blkno = blk - (reqpage - i);
bp->b_bcount = PAGE_SIZE * (j - i);
bp->b_bufsize = PAGE_SIZE * (j - i);
bp->b_pager.pg_reqpage = reqpage - i;
{
int k;
for (k = i; k < j; ++k) {
bp->b_pages[k - i] = m[k];
vm_page_flag_set(m[k], PG_SWAPINPROG);
}
}
bp->b_npages = j - i;
pbgetvp(swapdev_vp, bp);
cnt.v_swapin++;
cnt.v_swappgsin += bp->b_npages;
/*
* We still hold the lock on mreq, and our automatic completion routine
* does not remove it.
*/
vm_object_pip_add(mreq->object, bp->b_npages);
lastpindex = m[j-1]->pindex;
/*
* perform the I/O. NOTE!!! bp cannot be considered valid after
* this point because we automatically release it on completion.
* Instead, we look at the one page we are interested in which we
* still hold a lock on even through the I/O completion.
*
* The other pages in our m[] array are also released on completion,
* so we cannot assume they are valid anymore either.
*
* NOTE: b_blkno is destroyed by the call to VOP_STRATEGY
*/
VOP_STRATEGY(bp->b_vp, bp);
/*
* wait for the page we want to complete. PG_SWAPINPROG is always
* cleared on completion. If an I/O error occurs, SWAPBLK_NONE
* is set in the meta-data.
*/
s = splvm();
while ((mreq->flags & PG_SWAPINPROG) != 0) {
vm_page_flag_set(mreq, PG_WANTED | PG_REFERENCED);
cnt.v_intrans++;
if (tsleep(mreq, PSWP, "swread", hz*20)) {
printf(
"swap_pager: indefinite wait buffer: device:"
" %#lx, blkno: %ld, size: %ld\n",
(u_long)bp->b_dev, (long)bp->b_blkno,
(long)bp->b_bcount
);
}
}
splx(s);
/*
* mreq is left bussied after completion, but all the other pages
* are freed. If we had an unrecoverable read error the page will
* not be valid.
*/
if (mreq->valid != VM_PAGE_BITS_ALL) {
return(VM_PAGER_ERROR);
} else {
mreq->object->last_read = lastpindex;
return(VM_PAGER_OK);
}
/*
* A final note: in a low swap situation, we cannot deallocate swap
* and mark a page dirty here because the caller is likely to mark
* the page clean when we return, causing the page to possibly revert
* to all-zero's later.
*/
}
/*
* swap_pager_putpages:
*
* Assign swap (if necessary) and initiate I/O on the specified pages.
*
* We support both OBJT_DEFAULT and OBJT_SWAP objects. DEFAULT objects
* are automatically converted to SWAP objects.
*
* In a low memory situation we may block in VOP_STRATEGY(), but the new
* vm_page reservation system coupled with properly written VFS devices
* should ensure that no low-memory deadlock occurs. This is an area
* which needs work.
*
* The parent has N vm_object_pip_add() references prior to
* calling us and will remove references for rtvals[] that are
* not set to VM_PAGER_PEND. We need to remove the rest on I/O
* completion.
*
* The parent has soft-busy'd the pages it passes us and will unbusy
* those whos rtvals[] entry is not set to VM_PAGER_PEND on return.
* We need to unbusy the rest on I/O completion.
*/
void
swap_pager_putpages(object, m, count, sync, rtvals)
vm_object_t object;
vm_page_t *m;
int count;
boolean_t sync;
int *rtvals;
{
int i;
int n = 0;
#if !defined(MAX_PERF)
if (count && m[0]->object != object) {
panic("swap_pager_getpages: object mismatch %p/%p",
object,
m[0]->object
);
}
#endif
/*
* Step 1
*
* Turn object into OBJT_SWAP
* check for bogus sysops
* force sync if not pageout process
*/
if (object->type != OBJT_SWAP) {
swp_pager_meta_build(object, 0, SWAPBLK_NONE, 0);
}
if (curproc != pageproc)
sync = TRUE;
/*
* Step 2
*
* Assign swap blocks and issue I/O. We reallocate swap on the fly.
* The page is left dirty until the pageout operation completes
* successfully.
*/
for (i = 0; i < count; i += n) {
int s;
int j;
struct buf *bp;
daddr_t blk;
/*
* Maximum I/O size is limited by a number of factors.
*/
n = min(BLIST_MAX_ALLOC, count - i);
n = min(n, max_pageout_cluster);
/*
* Get biggest block of swap we can. If we fail, fall
* back and try to allocate a smaller block. Don't go
* overboard trying to allocate space if it would overly
* fragment swap.
*/
while (
(blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE &&
n > 4
) {
n >>= 1;
}
if (blk == SWAPBLK_NONE) {
for (j = 0; j < n; ++j) {
rtvals[i+j] = VM_PAGER_FAIL;
}
continue;
}
/*
* Oops, too big if it crosses a stripe
*
* 1111000000
* 111111
* 1000001
*/
if ((blk ^ (blk + n)) & dmmax_mask) {
j = ((blk + dmmax) & dmmax_mask) - blk;
swp_pager_freeswapspace(blk + j, n - j);
n = j;
}
/*
* All I/O parameters have been satisfied, build the I/O
* request and assign the swap space.
*
* NOTE: B_PAGING is set by pbgetvp()
*/
bp = getpbuf(&nsw_wcount);
bp->b_spc = NULL; /* not used, but NULL-out anyway */
pmap_qenter((vm_offset_t)bp->b_data, &m[i], n);
bp->b_flags = B_BUSY | B_ASYNC;
bp->b_proc = &proc0; /* XXX (but without B_PHYS this is ok) */
bp->b_rcred = bp->b_wcred = bp->b_proc->p_ucred;
if (bp->b_rcred != NOCRED)
crhold(bp->b_rcred);
if (bp->b_wcred != NOCRED)
crhold(bp->b_wcred);
pbgetvp(swapdev_vp, bp);
bp->b_bcount = PAGE_SIZE * n;
bp->b_bufsize = PAGE_SIZE * n;
bp->b_blkno = blk;
s = splvm();
for (j = 0; j < n; ++j) {
vm_page_t mreq = m[i+j];
swp_pager_meta_build(
mreq->object,
mreq->pindex,
blk + j,
0
);
vm_page_dirty(mreq);
rtvals[i+j] = VM_PAGER_OK;
vm_page_flag_set(mreq, PG_SWAPINPROG);
bp->b_pages[j] = mreq;
}
bp->b_flags |= B_CALL;
bp->b_npages = n;
cnt.v_swapout++;
cnt.v_swappgsout += bp->b_npages;
swapdev_vp->v_numoutput++;
/*
* asynchronous
*
* NOTE: b_blkno is destroyed by the call to VOP_STRATEGY
*/
if (sync == FALSE) {
bp->b_iodone = swp_pager_async_iodone;
bp->b_dirtyoff = 0;
bp->b_dirtyend = bp->b_bcount;
VOP_STRATEGY(bp->b_vp, bp);
for (j = 0; j < n; ++j)
rtvals[i+j] = VM_PAGER_PEND;
splx(s);
continue;
}
/*
* synchronous
*
* NOTE: b_blkno is destroyed by the call to VOP_STRATEGY
*/
bp->b_iodone = swp_pager_sync_iodone;
VOP_STRATEGY(bp->b_vp, bp);
/*
* Wait for the sync I/O to complete, then update rtvals.
* We just set the rtvals[] to VM_PAGER_PEND so we can call
* our async completion routine at the end, thus avoiding a
* double-free.
*/
while ((bp->b_flags & B_DONE) == 0) {
tsleep(bp, PVM, "swwrt", 0);
}
#if 0
if (bp->b_flags & B_ERROR) {
grv = VM_PAGER_ERROR;
}
#endif
for (j = 0; j < n; ++j)
rtvals[i+j] = VM_PAGER_PEND;
#if 0
if (bp->b_flags & B_ERROR) {
grv = VM_PAGER_ERROR;
}
#endif
/*
* Now that we are through with the bp, we can call the
* normal async completion, which frees everything up.
*/
swp_pager_async_iodone(bp);
splx(s);
}
}
/*
* swap_pager_sync_iodone:
*
* Completion routine for synchronous reads and writes from/to swap.
* We just mark the bp is complete and wake up anyone waiting on it.
*
* This routine may not block.
*/
static void
swp_pager_sync_iodone(bp)
struct buf *bp;
{
bp->b_flags |= B_DONE;
bp->b_flags &= ~B_ASYNC;
wakeup(bp);
}
/*
* swp_pager_async_iodone:
*
* Completion routine for asynchronous reads and writes from/to swap.
* Also called manually by synchronous code to finish up a bp.
*
* WARNING! This routine may be called from an interrupt. We cannot
* mess with swap metadata unless we want to run all our other routines
* at splbio() too, which I'd rather not do. We up ourselves
* to splvm() because we may call vm_page_free(), which can unlink a
* page from an object.
*
* XXX currently I do not believe any object routines protect
* object->memq at splvm(). The code must be gone over to determine
* the actual state of the problem.
*
* For READ operations, the pages are PG_BUSY'd. For WRITE operations,
* the pages are vm_page_t->busy'd. For READ operations, we PG_BUSY
* unbusy all pages except the 'main' request page. For WRITE
* operations, we vm_page_t->busy'd unbusy all pages ( we can do this
* because we marked them all VM_PAGER_PEND on return from putpages ).
*
* This routine may not block.
* This routine is called at splbio()
*/
static void
swp_pager_async_iodone(bp)
register struct buf *bp;
{
int s;
int i;
vm_object_t object = NULL;
s = splvm();
bp->b_flags |= B_DONE;
/*
* report error
*/
if (bp->b_flags & B_ERROR) {
printf(
"swap_pager: I/O error - %s failed; blkno %ld,"
"size %ld, error %d\n",
((bp->b_flags & B_READ) ? "pagein" : "pageout"),
(long)bp->b_blkno,
(long)bp->b_bcount,
bp->b_error
);
}
/*
* set object.
*/
if (bp->b_npages)
object = bp->b_pages[0]->object;
/*
* remove the mapping for kernel virtual
*/
pmap_qremove((vm_offset_t)bp->b_data, bp->b_npages);
/*
* cleanup pages. If an error occurs writing to swap, we are in
* very serious trouble. If it happens to be a disk error, though,
* we may be able to recover by reassigning the swap later on. So
* in this case we remove the m->swapblk assignment for the page
* but do not free it in the rlist. The errornous block(s) are thus
* never reallocated as swap. Redirty the page and continue.
*/
for (i = 0; i < bp->b_npages; ++i) {
vm_page_t m = bp->b_pages[i];
vm_page_flag_clear(m, PG_SWAPINPROG);
if (bp->b_flags & B_ERROR) {
/*
* If an error occurs I'd love to throw the swapblk
* away without freeing it back to swapspace, so it
* can never be used again. But I can't from an
* interrupt.
*/
if (bp->b_flags & B_READ) {
/*
* When reading, reqpage needs to stay
* locked for the parent, but all other
* pages can be freed. We still want to
* wakeup the parent waiting on the page,
* though. ( also: pg_reqpage can be -1 and
* not match anything ).
*
* We have to wake specifically requested pages
* up too because we cleared PG_SWAPINPROG and
* someone may be waiting for that.
*
* NOTE: for reads, m->dirty will probably
* be overriden by the original caller of
* getpages so don't play cute tricks here.
*
* XXX it may not be legal to free the page
* here as this messes with the object->memq's.
*/
m->valid = 0;
vm_page_flag_clear(m, PG_ZERO);
if (i != bp->b_pager.pg_reqpage)
vm_page_free(m);
else
vm_page_flash(m);
/*
* If i == bp->b_pager.pg_reqpage, do not wake
* the page up. The caller needs to.
*/
} else {
/*
* If a write error occurs, reactivate page
* so it doesn't clog the inactive list,
* then finish the I/O.
*/
vm_page_dirty(m);
vm_page_activate(m);
vm_page_io_finish(m);
}
} else if (bp->b_flags & B_READ) {
/*
* For read success, clear dirty bits. Nobody should
* have this page mapped but don't take any chances,
* make sure the pmap modify bits are also cleared.
*
* NOTE: for reads, m->dirty will probably be
* overriden by the original caller of getpages so
* we cannot set them in order to free the underlying
* swap in a low-swap situation. I don't think we'd
* want to do that anyway, but it was an optimization
* that existed in the old swapper for a time before
* it got ripped out due to precisely this problem.
*
* clear PG_ZERO in page.
*
* If not the requested page then deactivate it.
*
* Note that the requested page, reqpage, is left
* busied, but we still have to wake it up. The
* other pages are released (unbusied) by
* vm_page_wakeup(). We do not set reqpage's
* valid bits here, it is up to the caller.
*/
pmap_clear_modify(VM_PAGE_TO_PHYS(m));
m->valid = VM_PAGE_BITS_ALL;
m->dirty = 0;
vm_page_flag_clear(m, PG_ZERO);
/*
* We have to wake specifically requested pages
* up too because we cleared PG_SWAPINPROG and
* could be waiting for it in getpages. However,
* be sure to not unbusy getpages specifically
* requested page - getpages expects it to be
* left busy.
*/
if (i != bp->b_pager.pg_reqpage) {
vm_page_deactivate(m);
vm_page_wakeup(m);
} else {
vm_page_flash(m);
}
} else {
/*
* For write success, clear the modify and dirty
* status, then finish the I/O ( which decrements the
* busy count and possibly wakes waiter's up ).
*/
vm_page_protect(m, VM_PROT_READ);
pmap_clear_modify(VM_PAGE_TO_PHYS(m));
m->dirty = 0;
vm_page_io_finish(m);
}
}
/*
* adjust pip. NOTE: the original parent may still have its own
* pip refs on the object.
*/
if (object)
vm_object_pip_wakeupn(object, bp->b_npages);
/*
* release the physical I/O buffer
*/
relpbuf(bp, ((bp->b_flags & B_READ) ? &nsw_rcount : &nsw_wcount));
splx(s);
}
/************************************************************************
* SWAP META DATA *
************************************************************************
*
* These routines manipulate the swap metadata stored in the
* OBJT_SWAP object.
*
* In fact, we just have a few counters in the vm_object_t. The
* metadata is actually stored in a hash table.
*/
/*
* SWP_PAGER_HASH() - hash swap meta data
*
* This is an inline helper function which hash the swapblk given
* the object and page index. It returns a pointer to a pointer
* to the object, or a pointer to a NULL pointer if it could not
* find a swapblk.
*/
static __inline struct swblock **
swp_pager_hash(vm_object_t object, daddr_t index)
{
struct swblock **pswap;
struct swblock *swap;
index &= ~SWAP_META_MASK;
pswap = &swhash[(index ^ (int)(long)object) & swhash_mask];
while ((swap = *pswap) != NULL) {
if (swap->swb_object == object &&
swap->swb_index == index
) {
break;
}
pswap = &swap->swb_hnext;
}
return(pswap);
}
/*
* SWP_PAGER_META_BUILD() - add swap block to swap meta data for object
*
* We first convert the object to a swap object if it is a default
* object.
*
* The specified swapblk is added to the object's swap metadata. If
* the swapblk is not valid, it is freed instead. Any previously
* assigned swapblk is freed.
*/
static void
swp_pager_meta_build(
vm_object_t object,
daddr_t index,
daddr_t swapblk,
int waitok
) {
struct swblock *swap;
struct swblock **pswap;
/*
* Convert default object to swap object if necessary
*/
if (object->type != OBJT_SWAP) {
object->type = OBJT_SWAP;
object->un_pager.swp.swp_bcount = 0;
if (object->handle != NULL) {
TAILQ_INSERT_TAIL(
NOBJLIST(object->handle),
object,
pager_object_list
);
} else {
TAILQ_INSERT_TAIL(
&swap_pager_un_object_list,
object,
pager_object_list
);
}
}
/*
* Wait for free memory when waitok is TRUE prior to calling the
* zone allocator.
*/
while (waitok && cnt.v_free_count == 0) {
VM_WAIT;
}
/*
* If swapblk being added is invalid, just free it.
*/
if (swapblk & SWAPBLK_NONE) {
if (swapblk != SWAPBLK_NONE) {
swp_pager_freeswapspace(
index,
1
);
swapblk = SWAPBLK_NONE;
}
}
/*
* Locate hash entry. If not found create, but if we aren't adding
* anything just return.
*/
pswap = swp_pager_hash(object, index);
if ((swap = *pswap) == NULL) {
int i;
if (swapblk == SWAPBLK_NONE)
return;
swap = *pswap = zalloc(swap_zone);
swap->swb_hnext = NULL;
swap->swb_object = object;
swap->swb_index = index & ~SWAP_META_MASK;
swap->swb_count = 0;
++object->un_pager.swp.swp_bcount;
for (i = 0; i < SWAP_META_PAGES; ++i)
swap->swb_pages[i] = SWAPBLK_NONE;
}
/*
* Delete prior contents of metadata
*/
index &= SWAP_META_MASK;
if (swap->swb_pages[index] != SWAPBLK_NONE) {
swp_pager_freeswapspace(
swap->swb_pages[index] & SWAPBLK_MASK,
1
);
--swap->swb_count;
}
/*
* Enter block into metadata
*/
swap->swb_pages[index] = swapblk;
++swap->swb_count;
}
/*
* SWP_PAGER_META_FREE() - free a range of blocks in the object's swap metadata
*
* The requested range of blocks is freed, with any associated swap
* returned to the swap bitmap.
*
* This routine will free swap metadata structures as they are cleaned
* out. This routine does *NOT* operate on swap metadata associated
* with resident pages.
*
* This routine must be called at splvm()
*/
static void
swp_pager_meta_free(vm_object_t object, daddr_t index, daddr_t count)
{
if (object->type != OBJT_SWAP)
return;
while (count > 0) {
struct swblock **pswap;
struct swblock *swap;
pswap = swp_pager_hash(object, index);
if ((swap = *pswap) != NULL) {
daddr_t v = swap->swb_pages[index & SWAP_META_MASK];
if (v != SWAPBLK_NONE) {
swp_pager_freeswapspace(v, 1);
swap->swb_pages[index & SWAP_META_MASK] =
SWAPBLK_NONE;
if (--swap->swb_count == 0) {
*pswap = swap->swb_hnext;
zfree(swap_zone, swap);
--object->un_pager.swp.swp_bcount;
}
}
--count;
++index;
} else {
daddr_t n = SWAP_META_PAGES - (index & SWAP_META_MASK);
count -= n;
index += n;
}
}
}
/*
* SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object
*
* This routine locates and destroys all swap metadata associated with
* an object.
*/
static void
swp_pager_meta_free_all(vm_object_t object)
{
daddr_t index = 0;
if (object->type != OBJT_SWAP)
return;
while (object->un_pager.swp.swp_bcount) {
struct swblock **pswap;
struct swblock *swap;
pswap = swp_pager_hash(object, index);
if ((swap = *pswap) != NULL) {
int i;
for (i = 0; i < SWAP_META_PAGES; ++i) {
daddr_t v = swap->swb_pages[i];
if (v != SWAPBLK_NONE) {
#if !defined(MAX_PERF)
--swap->swb_count;
#endif
swp_pager_freeswapspace(
v,
1
);
}
}
#if !defined(MAX_PERF)
if (swap->swb_count != 0)
panic("swap_pager_meta_free_all: swb_count != 0");
#endif
*pswap = swap->swb_hnext;
zfree(swap_zone, swap);
--object->un_pager.swp.swp_bcount;
}
index += SWAP_META_PAGES;
#if !defined(MAX_PERF)
if (index > 0x20000000)
panic("swp_pager_meta_free_all: failed to locate all swap meta blocks");
#endif
}
}
/*
* SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data.
*
* This routine is capable of looking up, popping, or freeing
* swapblk assignments in the swap meta data or in the vm_page_t.
* The routine typically returns the swapblk being looked-up, or popped,
* or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block
* was invalid. This routine will automatically free any invalid
* meta-data swapblks.
*
* It is not possible to store invalid swapblks in the swap meta data
* (other then a literal 'SWAPBLK_NONE'), so we don't bother checking.
*
* When acting on a busy resident page and paging is in progress, we
* have to wait until paging is complete but otherwise can act on the
* busy page.
*
* SWM_FREE remove and free swap block from metadata
*
* SWM_POP remove from meta data but do not free.. pop it out
*/
static daddr_t
swp_pager_meta_ctl(
vm_object_t object,
vm_pindex_t index,
int flags
) {
/*
* The meta data only exists of the object is OBJT_SWAP
* and even then might not be allocated yet.
*/
if (
object->type != OBJT_SWAP ||
object->un_pager.swp.swp_bcount == 0
) {
return(SWAPBLK_NONE);
}
{
struct swblock **pswap;
struct swblock *swap;
daddr_t r1 = SWAPBLK_NONE;
pswap = swp_pager_hash(object, index);
index &= SWAP_META_MASK;
if ((swap = *pswap) != NULL) {
r1 = swap->swb_pages[index];
if (r1 != SWAPBLK_NONE) {
if (flags & SWM_FREE) {
swp_pager_freeswapspace(
r1,
1
);
r1 = SWAPBLK_NONE;
}
if (flags & (SWM_FREE|SWM_POP)) {
swap->swb_pages[index] = SWAPBLK_NONE;
if (--swap->swb_count == 0) {
*pswap = swap->swb_hnext;
zfree(swap_zone, swap);
--object->un_pager.swp.swp_bcount;
}
}
}
}
return(r1);
}
/* not reached */
}
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