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freebsd-dev/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
*
* $FreeBSD$
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/sysctl.h>
#include <sys/blist.h>
#include <sys/lock.h>
#include <sys/sx.h>
#include <sys/vmmeter.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/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_kern.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/uma.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 (task killing) */
static int swap_pager_almost_full; /* swap space exhaustion (w/ hysteresis)*/
static int nsw_rcount; /* free read buffers */
static int nsw_wcount_sync; /* limit write buffers / synchronous */
static int nsw_wcount_async; /* limit write buffers / asynchronous */
static int nsw_wcount_async_max;/* assigned maximum */
static int nsw_cluster_max; /* maximum VOP I/O allowed */
struct blist *swapblist;
static struct swblock **swhash;
static int swhash_mask;
static int swap_async_max = 4; /* maximum in-progress async I/O's */
static struct sx sw_alloc_sx;
/* from vm_swap.c */
extern struct vnode *swapdev_vp;
extern struct swdevt *swdevt;
extern int nswdev;
SYSCTL_INT(_vm, OID_AUTO, swap_async_max,
CTLFLAG_RW, &swap_async_max, 0, "Maximum running async swap ops");
#define BLK2DEVIDX(blk) (nswdev > 1 ? blk / dmmax % nswdev : 0)
/*
* "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)(intptr_t)handle >> 4) & (NOBJLISTS-1)])
static struct mtx sw_alloc_mtx; /* protect list manipulation */
static struct pagerlst swap_pager_object_list[NOBJLISTS];
struct pagerlst swap_pager_un_object_list;
uma_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(void *handle, vm_ooffset_t size,
vm_prot_t prot, vm_ooffset_t offset);
static void swap_pager_dealloc(vm_object_t object);
static int swap_pager_getpages(vm_object_t, vm_page_t *, int, int);
static void swap_pager_init(void);
static void swap_pager_unswapped(vm_page_t);
static void swap_pager_strategy(vm_object_t, struct bio *);
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 */
swap_pager_strategy /* pager strategy call */
};
static struct buf *getchainbuf(struct bio *bp, struct vnode *vp, int flags);
static void flushchainbuf(struct buf *nbp);
static void waitchainbuf(struct bio *bp, int count, int done);
/*
* dmmax is in page-sized chunks with the new swap system. It was
* dev-bsized chunks in the old. dmmax is always a power of 2.
*
* swap_*() routines are externally accessible. swp_*() routines are
* internal.
*/
int dmmax;
static int dmmax_mask;
int nswap_lowat = 128; /* in pages, swap_pager_almost_full warn */
int nswap_hiwat = 512; /* in pages, swap_pager_almost_full warn */
SYSCTL_INT(_vm, OID_AUTO, dmmax,
CTLFLAG_RD, &dmmax, 0, "Maximum size of a swap block");
static __inline void swp_sizecheck(void);
static void swp_pager_sync_iodone(struct buf *bp);
static void swp_pager_async_iodone(struct buf *bp);
/*
* Swap bitmap functions
*/
static __inline void swp_pager_freeswapspace(daddr_t blk, int npages);
static __inline daddr_t swp_pager_getswapspace(int npages);
/*
* Metadata functions
*/
static void swp_pager_meta_build(vm_object_t, vm_pindex_t, daddr_t);
static void swp_pager_meta_free(vm_object_t, vm_pindex_t, daddr_t);
static void swp_pager_meta_free_all(vm_object_t);
static daddr_t swp_pager_meta_ctl(vm_object_t, vm_pindex_t, int);
/*
* SWP_SIZECHECK() - update swap_pager_full indication
*
* update the swap_pager_almost_full indication and warn when we are
* about to run out of swap space, using lowat/hiwat hysteresis.
*
* Clear swap_pager_full ( task killing ) indication when lowat is met.
*
* No restrictions on call
* This routine may not block.
* This routine must be called at splvm()
*/
static __inline void
swp_sizecheck()
{
GIANT_REQUIRED;
if (vm_swap_size < nswap_lowat) {
if (swap_pager_almost_full == 0) {
printf("swap_pager: out of swap space\n");
swap_pager_almost_full = 1;
}
} else {
swap_pager_full = 0;
if (vm_swap_size > nswap_hiwat)
swap_pager_almost_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);
mtx_init(&sw_alloc_mtx, "swap_pager list", NULL, MTX_DEF);
/*
* 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, n2;
/*
* 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 nsw_cluster_max 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.
*
* Currently we hardwire nsw_wcount_async to 4. This limit is
* designed to prevent other I/O from having high latencies due to
* our pageout I/O. The value 4 works well for one or two active swap
* devices but is probably a little low if you have more. Even so,
* a higher value would probably generate only a limited improvement
* with three or four active swap devices since the system does not
* typically have to pageout at extreme bandwidths. We will want
* at least 2 per swap devices, and 4 is a pretty good value if you
* have one NFS swap device due to the command/ack latency over NFS.
* So it all works out pretty well.
*/
nsw_cluster_max = min((MAXPHYS/PAGE_SIZE), MAX_PAGEOUT_CLUSTER);
mtx_lock(&pbuf_mtx);
nsw_rcount = (nswbuf + 1) / 2;
nsw_wcount_sync = (nswbuf + 3) / 4;
nsw_wcount_async = 4;
nsw_wcount_async_max = nsw_wcount_async;
mtx_unlock(&pbuf_mtx);
/*
* 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. This reservation
* is typically limited to around 32MB by default.
*/
n = cnt.v_page_count / 2;
if (maxswzone && n > maxswzone / sizeof(struct swblock))
n = maxswzone / sizeof(struct swblock);
n2 = n;
swap_zone = uma_zcreate("SWAPMETA", sizeof(struct swblock), NULL, NULL,
NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
do {
if (uma_zone_set_obj(swap_zone, NULL, n))
break;
/*
* if the allocation failed, try a zone two thirds the
* size of the previous attempt.
*/
n -= ((n + 2) / 3);
} while (n > 0);
if (swap_zone == NULL)
panic("failed to create swap_zone.");
if (n2 != n)
printf("Swap zone entries reduced from %d to %d.\n", n2, n);
n2 = n;
/*
* 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 < n2 / 8; n *= 2)
;
swhash = malloc(sizeof(struct swblock *) * n, M_VMPGDATA, M_WAITOK | M_ZERO);
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.
*
* MPSAFE
*/
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;
mtx_lock(&Giant);
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.
*/
sx_xlock(&sw_alloc_sx);
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);
}
sx_xunlock(&sw_alloc_sx);
} else {
object = vm_object_allocate(OBJT_DEFAULT,
OFF_TO_IDX(offset + PAGE_MASK + size));
swp_pager_meta_build(object, 0, SWAPBLK_NONE);
}
mtx_unlock(&Giant);
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;
{
int s;
GIANT_REQUIRED;
/*
* Remove from list right away so lookups will fail if we block for
* pageout completion.
*/
mtx_lock(&sw_alloc_mtx);
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);
}
mtx_unlock(&sw_alloc_mtx);
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.
*/
s = splvm();
swp_pager_meta_free_all(object);
splx(s);
}
/************************************************************************
* 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;
GIANT_REQUIRED;
if ((blk = blist_alloc(swapblist, npages)) == SWAPBLK_NONE) {
if (swap_pager_full != 2) {
printf("swap_pager_getswapspace: failed\n");
swap_pager_full = 2;
swap_pager_almost_full = 1;
}
} else {
vm_swap_size -= npages;
/* per-swap area stats */
swdevt[BLK2DEVIDX(blk)].sw_used += 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;
{
GIANT_REQUIRED;
blist_free(swapblist, blk, npages);
vm_swap_size += npages;
/* per-swap area stats */
swdevt[BLK2DEVIDX(blk)].sw_used -= 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.
*
* This routine may be called at any spl. We up our spl to splvm temporarily
* in order to perform the metadata removal.
*/
void
swap_pager_freespace(object, start, size)
vm_object_t object;
vm_pindex_t start;
vm_size_t size;
{
int s = splvm();
GIANT_REQUIRED;
swp_pager_meta_free(object, start, size);
splx(s);
}
/*
* SWAP_PAGER_RESERVE() - reserve swap blocks in object
*
* Assigns swap blocks to the specified range within the object. The
* swap blocks are not zerod. Any previous swap assignment is destroyed.
*
* Returns 0 on success, -1 on failure.
*/
int
swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_size_t size)
{
int s;
int n = 0;
daddr_t blk = SWAPBLK_NONE;
vm_pindex_t beg = start; /* save start index */
s = splvm();
while (size) {
if (n == 0) {
n = BLIST_MAX_ALLOC;
while ((blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE) {
n >>= 1;
if (n == 0) {
swp_pager_meta_free(object, beg, start - beg);
splx(s);
return (-1);
}
}
}
swp_pager_meta_build(object, start, blk);
--size;
++start;
++blk;
--n;
}
swp_pager_meta_free(object, start, n);
splx(s);
return (0);
}
/*
* 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.
*
* This routine can be called at any spl
*
* 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;
int s;
GIANT_REQUIRED;
s = splvm();
/*
* If destroysource is set, we remove the source object from the
* swap_pager internal queue now.
*/
if (destroysource) {
mtx_lock(&sw_alloc_mtx);
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
);
}
mtx_unlock(&sw_alloc_mtx);
}
/*
* 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);
} 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 consistency since we've removed the object from its
* queues.
*/
srcobject->type = OBJT_DEFAULT;
}
splx(s);
}
/*
* 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;
int s;
/*
* do we have good backing store at the requested index ?
*/
s = splvm();
blk0 = swp_pager_meta_ctl(object, pindex, 0);
if (blk0 == SWAPBLK_NONE) {
splx(s);
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 != 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 != blk0 + i)
break;
}
*after = (i - 1);
}
splx(s);
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
* This routine must be called at splvm()
*/
static void
swap_pager_unswapped(m)
vm_page_t m;
{
swp_pager_meta_ctl(m->object, m->pindex, SWM_FREE);
}
/*
* SWAP_PAGER_STRATEGY() - read, write, free blocks
*
* This implements the vm_pager_strategy() interface to swap and allows
* other parts of the system to directly access swap as backing store
* through vm_objects of type OBJT_SWAP. This is intended to be a
* cacheless interface ( i.e. caching occurs at higher levels ).
* Therefore we do not maintain any resident pages. All I/O goes
* directly to and from the swap device.
*
* Note that b_blkno is scaled for PAGE_SIZE
*
* We currently attempt to run I/O synchronously or asynchronously as
* the caller requests. This isn't perfect because we loose error
* sequencing when we run multiple ops in parallel to satisfy a request.
* But this is swap, so we let it all hang out.
*/
static void
swap_pager_strategy(vm_object_t object, struct bio *bp)
{
vm_pindex_t start;
int count;
int s;
char *data;
struct buf *nbp = NULL;
GIANT_REQUIRED;
/* XXX: KASSERT instead ? */
if (bp->bio_bcount & PAGE_MASK) {
biofinish(bp, NULL, EINVAL);
printf("swap_pager_strategy: bp %p blk %d size %d, not page bounded\n", bp, (int)bp->bio_pblkno, (int)bp->bio_bcount);
return;
}
/*
* Clear error indication, initialize page index, count, data pointer.
*/
bp->bio_error = 0;
bp->bio_flags &= ~BIO_ERROR;
bp->bio_resid = bp->bio_bcount;
*(u_int *) &bp->bio_driver1 = 0;
start = bp->bio_pblkno;
count = howmany(bp->bio_bcount, PAGE_SIZE);
data = bp->bio_data;
s = splvm();
/*
* Deal with BIO_DELETE
*/
if (bp->bio_cmd == BIO_DELETE) {
/*
* FREE PAGE(s) - destroy underlying swap that is no longer
* needed.
*/
swp_pager_meta_free(object, start, count);
splx(s);
bp->bio_resid = 0;
biodone(bp);
return;
}
/*
* Execute read or write
*/
while (count > 0) {
daddr_t blk;
/*
* Obtain block. If block not found and writing, allocate a
* new block and build it into the object.
*/
blk = swp_pager_meta_ctl(object, start, 0);
if ((blk == SWAPBLK_NONE) && (bp->bio_cmd == BIO_WRITE)) {
blk = swp_pager_getswapspace(1);
if (blk == SWAPBLK_NONE) {
bp->bio_error = ENOMEM;
bp->bio_flags |= BIO_ERROR;
break;
}
swp_pager_meta_build(object, start, blk);
}
/*
* Do we have to flush our current collection? Yes if:
*
* - no swap block at this index
* - swap block is not contiguous
* - we cross a physical disk boundry in the
* stripe.
*/
if (
nbp && (nbp->b_blkno + btoc(nbp->b_bcount) != blk ||
((nbp->b_blkno ^ blk) & dmmax_mask)
)
) {
splx(s);
if (bp->bio_cmd == BIO_READ) {
++cnt.v_swapin;
cnt.v_swappgsin += btoc(nbp->b_bcount);
} else {
++cnt.v_swapout;
cnt.v_swappgsout += btoc(nbp->b_bcount);
nbp->b_dirtyend = nbp->b_bcount;
}
flushchainbuf(nbp);
s = splvm();
nbp = NULL;
}
/*
* Add new swapblk to nbp, instantiating nbp if necessary.
* Zero-fill reads are able to take a shortcut.
*/
if (blk == SWAPBLK_NONE) {
/*
* We can only get here if we are reading. Since
* we are at splvm() we can safely modify b_resid,
* even if chain ops are in progress.
*/
bzero(data, PAGE_SIZE);
bp->bio_resid -= PAGE_SIZE;
} else {
if (nbp == NULL) {
nbp = getchainbuf(bp, swapdev_vp, B_ASYNC);
nbp->b_blkno = blk;
nbp->b_bcount = 0;
nbp->b_data = data;
}
nbp->b_bcount += PAGE_SIZE;
}
--count;
++start;
data += PAGE_SIZE;
}
/*
* Flush out last buffer
*/
splx(s);
if (nbp) {
if (nbp->b_iocmd == BIO_READ) {
++cnt.v_swapin;
cnt.v_swappgsin += btoc(nbp->b_bcount);
} else {
++cnt.v_swapout;
cnt.v_swappgsout += btoc(nbp->b_bcount);
nbp->b_dirtyend = nbp->b_bcount;
}
flushchainbuf(nbp);
/* nbp = NULL; */
}
/*
* Wait for completion.
*/
waitchainbuf(bp, 0, 1);
}
/*
* 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;
GIANT_REQUIRED;
mreq = m[reqpage];
if (mreq->object != object) {
panic("swap_pager_getpages: object mismatch %p/%p",
object,
mreq->object
);
}
/*
* 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. Note that blk, iblk & jblk can be SWAPBLK_NONE, but the
* loops are set up such that the case(s) are handled implicitly.
*
* The swp_*() calls must be made at splvm(). vm_page_free() does
* not need to be, but it will go a little faster if it is.
*/
s = splvm();
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 (blk != iblk + (reqpage - i))
break;
if ((blk ^ iblk) & dmmax_mask)
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 (blk != jblk - (j - reqpage))
break;
if ((blk ^ jblk) & dmmax_mask)
break;
}
/*
* free pages outside our collection range. Note: we never free
* mreq, it must remain busy throughout.
*/
vm_page_lock_queues();
{
int k;
for (k = 0; k < i; ++k)
vm_page_free(m[k]);
for (k = j; k < count; ++k)
vm_page_free(m[k]);
}
vm_page_unlock_queues();
splx(s);
/*
* 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_iocmd = BIO_READ;
bp->b_iodone = swp_pager_async_iodone;
bp->b_rcred = crhold(thread0.td_ucred);
bp->b_wcred = crhold(thread0.td_ucred);
bp->b_data = (caddr_t) kva;
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
*/
BUF_KERNPROC(bp);
BUF_STRATEGY(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:"
" %s, blkno: %ld, size: %ld\n",
devtoname(bp->b_dev), (long)bp->b_blkno,
bp->b_bcount
);
}
}
splx(s);
/*
* mreq is left busied 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 {
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;
GIANT_REQUIRED;
if (count && m[0]->object != object) {
panic("swap_pager_getpages: object mismatch %p/%p",
object,
m[0]->object
);
}
/*
* 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);
if (curproc != pageproc)
sync = TRUE;
/*
* Step 2
*
* Update nsw parameters from swap_async_max sysctl values.
* Do not let the sysop crash the machine with bogus numbers.
*/
mtx_lock(&pbuf_mtx);
if (swap_async_max != nsw_wcount_async_max) {
int n;
int s;
/*
* limit range
*/
if ((n = swap_async_max) > nswbuf / 2)
n = nswbuf / 2;
if (n < 1)
n = 1;
swap_async_max = n;
/*
* Adjust difference ( if possible ). If the current async
* count is too low, we may not be able to make the adjustment
* at this time.
*/
s = splvm();
n -= nsw_wcount_async_max;
if (nsw_wcount_async + n >= 0) {
nsw_wcount_async += n;
nsw_wcount_async_max += n;
wakeup(&nsw_wcount_async);
}
splx(s);
}
mtx_unlock(&pbuf_mtx);
/*
* Step 3
*
* 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, nsw_cluster_max);
s = splvm();
/*
* 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;
splx(s);
continue;
}
/*
* The I/O we are constructing cannot cross a physical
* disk boundry in the swap stripe. Note: we are still
* at splvm().
*/
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()
*/
if (sync == TRUE) {
bp = getpbuf(&nsw_wcount_sync);
} else {
bp = getpbuf(&nsw_wcount_async);
bp->b_flags = B_ASYNC;
}
bp->b_iocmd = BIO_WRITE;
bp->b_spc = NULL; /* not used, but NULL-out anyway */
pmap_qenter((vm_offset_t)bp->b_data, &m[i], n);
bp->b_rcred = crhold(thread0.td_ucred);
bp->b_wcred = crhold(thread0.td_ucred);
bp->b_bcount = PAGE_SIZE * n;
bp->b_bufsize = PAGE_SIZE * n;
bp->b_blkno = blk;
pbgetvp(swapdev_vp, bp);
for (j = 0; j < n; ++j) {
vm_page_t mreq = m[i+j];
swp_pager_meta_build(
mreq->object,
mreq->pindex,
blk + j
);
vm_page_dirty(mreq);
rtvals[i+j] = VM_PAGER_OK;
vm_page_flag_set(mreq, PG_SWAPINPROG);
bp->b_pages[j] = mreq;
}
bp->b_npages = n;
/*
* Must set dirty range for NFS to work.
*/
bp->b_dirtyoff = 0;
bp->b_dirtyend = bp->b_bcount;
cnt.v_swapout++;
cnt.v_swappgsout += bp->b_npages;
VI_LOCK(swapdev_vp);
swapdev_vp->v_numoutput++;
VI_UNLOCK(swapdev_vp);
splx(s);
/*
* asynchronous
*
* NOTE: b_blkno is destroyed by the call to VOP_STRATEGY
*/
if (sync == FALSE) {
bp->b_iodone = swp_pager_async_iodone;
BUF_KERNPROC(bp);
BUF_STRATEGY(bp);
for (j = 0; j < n; ++j)
rtvals[i+j] = VM_PAGER_PEND;
/* restart outter loop */
continue;
}
/*
* synchronous
*
* NOTE: b_blkno is destroyed by the call to VOP_STRATEGY
*/
bp->b_iodone = swp_pager_sync_iodone;
BUF_STRATEGY(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.
*/
s = splbio();
while ((bp->b_flags & B_DONE) == 0) {
tsleep(bp, PVM, "swwrt", 0);
}
for (j = 0; j < n; ++j)
rtvals[i+j] = VM_PAGER_PEND;
/*
* 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. This routine is called at splbio() or better.
*/
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.
*
* 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() or better
*
* We up ourselves to splvm() as required for various vm_page related
* calls.
*/
static void
swp_pager_async_iodone(bp)
struct buf *bp;
{
int s;
int i;
vm_object_t object = NULL;
GIANT_REQUIRED;
bp->b_flags |= B_DONE;
/*
* report error
*/
if (bp->b_ioflags & BIO_ERROR) {
printf(
"swap_pager: I/O error - %s failed; blkno %ld,"
"size %ld, error %d\n",
((bp->b_iocmd == BIO_READ) ? "pagein" : "pageout"),
(long)bp->b_blkno,
(long)bp->b_bcount,
bp->b_error
);
}
/*
* set object, raise to splvm().
*/
if (bp->b_npages)
object = bp->b_pages[0]->object;
s = splvm();
/*
* remove the mapping for kernel virtual
*/
pmap_qremove((vm_offset_t)bp->b_data, bp->b_npages);
vm_page_lock_queues();
/*
* 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_ioflags & BIO_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_iocmd == BIO_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 overridden by the original caller of
* getpages so don't play cute tricks here.
*
* XXX IT IS NOT LEGAL TO FREE THE PAGE HERE
* AS THIS MESSES WITH object->memq, and it is
* not legal to mess with object->memq from an
* interrupt.
*/
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_iocmd == BIO_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
* overridden 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(m);
m->valid = VM_PAGE_BITS_ALL;
vm_page_undirty(m);
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 ).
*/
pmap_clear_modify(m);
vm_page_undirty(m);
vm_page_io_finish(m);
if (!vm_page_count_severe() || !vm_page_try_to_cache(m))
pmap_page_protect(m, VM_PROT_READ);
}
}
vm_page_unlock_queues();
/*
* 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_iocmd == BIO_READ) ? &nsw_rcount :
((bp->b_flags & B_ASYNC) ?
&nsw_wcount_async :
&nsw_wcount_sync
)
)
);
splx(s);
}
/************************************************************************
* SWAP META DATA *
************************************************************************
*
* These routines manipulate the swap metadata stored in the
* OBJT_SWAP object. All swp_*() routines must be called at
* splvm() because swap can be freed up by the low level vm_page
* code which might be called from interrupts beyond what splbio() covers.
*
* Swap metadata is implemented with a global hash and not directly
* linked into the object. Instead the object simply contains
* appropriate tracking counters.
*/
/*
* SWP_PAGER_HASH() - hash swap meta data
*
* This is an inline helper function which hashes 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.
*
* This routine must be called at splvm().
*/
static __inline struct swblock **
swp_pager_hash(vm_object_t object, vm_pindex_t index)
{
struct swblock **pswap;
struct swblock *swap;
index &= ~(vm_pindex_t)SWAP_META_MASK;
pswap = &swhash[(index ^ (int)(intptr_t)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.
*
* This routine must be called at splvm(), except when used to convert
* an OBJT_DEFAULT object into an OBJT_SWAP object.
*/
static void
swp_pager_meta_build(
vm_object_t object,
vm_pindex_t pindex,
daddr_t swapblk
) {
struct swblock *swap;
struct swblock **pswap;
int idx;
GIANT_REQUIRED;
/*
* Convert default object to swap object if necessary
*/
if (object->type != OBJT_SWAP) {
object->type = OBJT_SWAP;
object->un_pager.swp.swp_bcount = 0;
mtx_lock(&sw_alloc_mtx);
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
);
}
mtx_unlock(&sw_alloc_mtx);
}
/*
* Locate hash entry. If not found create, but if we aren't adding
* anything just return. If we run out of space in the map we wait
* and, since the hash table may have changed, retry.
*/
retry:
pswap = swp_pager_hash(object, pindex);
if ((swap = *pswap) == NULL) {
int i;
if (swapblk == SWAPBLK_NONE)
return;
swap = *pswap = uma_zalloc(swap_zone, M_NOWAIT);
if (swap == NULL) {
VM_WAIT;
goto retry;
}
swap->swb_hnext = NULL;
swap->swb_object = object;
swap->swb_index = pindex & ~(vm_pindex_t)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
*/
idx = pindex & SWAP_META_MASK;
if (swap->swb_pages[idx] != SWAPBLK_NONE) {
swp_pager_freeswapspace(swap->swb_pages[idx], 1);
--swap->swb_count;
}
/*
* Enter block into metadata
*/
swap->swb_pages[idx] = swapblk;
if (swapblk != SWAPBLK_NONE)
++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, vm_pindex_t index, daddr_t count)
{
GIANT_REQUIRED;
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;
uma_zfree(swap_zone, swap);
--object->un_pager.swp.swp_bcount;
}
}
--count;
++index;
} else {
int 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.
*
* This routine must be called at splvm()
*/
static void
swp_pager_meta_free_all(vm_object_t object)
{
daddr_t index = 0;
GIANT_REQUIRED;
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) {
--swap->swb_count;
swp_pager_freeswapspace(v, 1);
}
}
if (swap->swb_count != 0)
panic("swap_pager_meta_free_all: swb_count != 0");
*pswap = swap->swb_hnext;
uma_zfree(swap_zone, swap);
--object->un_pager.swp.swp_bcount;
}
index += SWAP_META_PAGES;
if (index > 0x20000000)
panic("swp_pager_meta_free_all: failed to locate all swap meta blocks");
}
}
/*
* 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.
*
* This routine must be called at splvm().
*
* 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 pindex,
int flags
) {
struct swblock **pswap;
struct swblock *swap;
daddr_t r1;
int idx;
GIANT_REQUIRED;
/*
* The meta data only exists of the object is OBJT_SWAP
* and even then might not be allocated yet.
*/
if (object->type != OBJT_SWAP)
return (SWAPBLK_NONE);
r1 = SWAPBLK_NONE;
pswap = swp_pager_hash(object, pindex);
if ((swap = *pswap) != NULL) {
idx = pindex & SWAP_META_MASK;
r1 = swap->swb_pages[idx];
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[idx] = SWAPBLK_NONE;
if (--swap->swb_count == 0) {
*pswap = swap->swb_hnext;
uma_zfree(swap_zone, swap);
--object->un_pager.swp.swp_bcount;
}
}
}
}
return (r1);
}
/********************************************************
* CHAINING FUNCTIONS *
********************************************************
*
* These functions support recursion of I/O operations
* on bp's, typically by chaining one or more 'child' bp's
* to the parent. Synchronous, asynchronous, and semi-synchronous
* chaining is possible.
*/
/*
* vm_pager_chain_iodone:
*
* io completion routine for child bp. Currently we fudge a bit
* on dealing with b_resid. Since users of these routines may issue
* multiple children simultaneously, sequencing of the error can be lost.
*/
static void
vm_pager_chain_iodone(struct buf *nbp)
{
struct bio *bp;
u_int *count;
bp = nbp->b_caller1;
count = (u_int *)&(bp->bio_driver1);
if (bp != NULL) {
if (nbp->b_ioflags & BIO_ERROR) {
bp->bio_flags |= BIO_ERROR;
bp->bio_error = nbp->b_error;
} else if (nbp->b_resid != 0) {
bp->bio_flags |= BIO_ERROR;
bp->bio_error = EINVAL;
} else {
bp->bio_resid -= nbp->b_bcount;
}
nbp->b_caller1 = NULL;
--(*count);
if (bp->bio_flags & BIO_FLAG1) {
bp->bio_flags &= ~BIO_FLAG1;
wakeup(bp);
}
}
nbp->b_flags |= B_DONE;
nbp->b_flags &= ~B_ASYNC;
relpbuf(nbp, NULL);
}
/*
* getchainbuf:
*
* Obtain a physical buffer and chain it to its parent buffer. When
* I/O completes, the parent buffer will be B_SIGNAL'd. Errors are
* automatically propagated to the parent
*/
static struct buf *
getchainbuf(struct bio *bp, struct vnode *vp, int flags)
{
struct buf *nbp;
u_int *count;
GIANT_REQUIRED;
nbp = getpbuf(NULL);
count = (u_int *)&(bp->bio_driver1);
nbp->b_caller1 = bp;
++(*count);
if (*count > 4)
waitchainbuf(bp, 4, 0);
nbp->b_iocmd = bp->bio_cmd;
nbp->b_ioflags = 0;
nbp->b_flags = flags;
nbp->b_rcred = crhold(thread0.td_ucred);
nbp->b_wcred = crhold(thread0.td_ucred);
nbp->b_iodone = vm_pager_chain_iodone;
if (vp)
pbgetvp(vp, nbp);
return (nbp);
}
static void
flushchainbuf(struct buf *nbp)
{
GIANT_REQUIRED;
if (nbp->b_bcount) {
nbp->b_bufsize = nbp->b_bcount;
if (nbp->b_iocmd == BIO_WRITE)
nbp->b_dirtyend = nbp->b_bcount;
BUF_KERNPROC(nbp);
BUF_STRATEGY(nbp);
} else {
bufdone(nbp);
}
}
static void
waitchainbuf(struct bio *bp, int limit, int done)
{
int s;
u_int *count;
GIANT_REQUIRED;
count = (u_int *)&(bp->bio_driver1);
s = splbio();
while (*count > limit) {
bp->bio_flags |= BIO_FLAG1;
tsleep(bp, PRIBIO + 4, "bpchain", 0);
}
if (done) {
if (bp->bio_resid != 0 && !(bp->bio_flags & BIO_ERROR)) {
bp->bio_flags |= BIO_ERROR;
bp->bio_error = EINVAL;
}
biodone(bp);
}
splx(s);
}
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