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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) 1982, 1986, 1989, 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
* @(#)vm_swap.c 8.5 (Berkeley) 2/17/94
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_mac.h"
#include "opt_swap.h"
#include "opt_vm.h"
#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/disk.h>
#include <sys/fcntl.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/vnode.h>
#include <sys/mac.h>
#include <sys/malloc.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/blist.h>
#include <sys/lock.h>
#include <sys/sx.h>
#include <sys/vmmeter.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/vm_param.h>
#include <vm/swap_pager.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#include <geom/geom.h>
/*
* SWB_NPAGES must be a power of 2. It may be set to 1, 2, 4, 8, or 16
* pages per allocation. We recommend you stick with the default of 8.
* The 16-page limit is due to the radix code (kern/subr_blist.c).
*/
#ifndef MAX_PAGEOUT_CLUSTER
#define MAX_PAGEOUT_CLUSTER 16
#endif
#if !defined(SWB_NPAGES)
#define SWB_NPAGES MAX_PAGEOUT_CLUSTER
#endif
/*
* Piecemeal swap metadata structure. Swap is stored in a radix tree.
*
* If SWB_NPAGES is 8 and sizeof(char *) == sizeof(daddr_t), our radix
* is basically 8. Assuming PAGE_SIZE == 4096, one tree level represents
* 32K worth of data, two levels represent 256K, three levels represent
* 2 MBytes. This is acceptable.
*
* Overall memory utilization is about the same as the old swap structure.
*/
#define SWCORRECT(n) (sizeof(void *) * (n) / sizeof(daddr_t))
#define SWAP_META_PAGES (SWB_NPAGES * 2)
#define SWAP_META_MASK (SWAP_META_PAGES - 1)
typedef int32_t swblk_t; /*
* swap offset. This is the type used to
* address the "virtual swap device" and
* therefore the maximum swap space is
* 2^32 pages.
*/
struct swdevt;
typedef void sw_strategy_t(struct buf *bp, struct swdevt *sw);
typedef void sw_close_t(struct thread *td, struct swdevt *sw);
/*
* Swap device table
*/
struct swdevt {
int sw_flags;
int sw_nblks;
int sw_used;
dev_t sw_dev;
struct vnode *sw_vp;
void *sw_id;
swblk_t sw_first;
swblk_t sw_end;
struct blist *sw_blist;
TAILQ_ENTRY(swdevt) sw_list;
sw_strategy_t *sw_strategy;
sw_close_t *sw_close;
};
#define SW_CLOSING 0x04
struct swblock {
struct swblock *swb_hnext;
vm_object_t swb_object;
vm_pindex_t swb_index;
int swb_count;
daddr_t swb_pages[SWAP_META_PAGES];
};
static struct mtx sw_dev_mtx;
static TAILQ_HEAD(, swdevt) swtailq = TAILQ_HEAD_INITIALIZER(swtailq);
static struct swdevt *swdevhd; /* Allocate from here next */
static int nswapdev; /* Number of swap devices */
int swap_pager_avail;
static int swdev_syscall_active = 0; /* serialize swap(on|off) */
static void swapdev_strategy(struct buf *, struct swdevt *sw);
#define SWM_FREE 0x02 /* free, period */
#define SWM_POP 0x04 /* pop out */
int swap_pager_full = 2; /* swap space exhaustion (task killing) */
static int swap_pager_almost_full = 1; /* 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 */
static struct swblock **swhash;
static int swhash_mask;
static struct mtx swhash_mtx;
static int swap_async_max = 4; /* maximum in-progress async I/O's */
static struct sx sw_alloc_sx;
SYSCTL_INT(_vm, OID_AUTO, swap_async_max,
CTLFLAG_RW, &swap_async_max, 0, "Maximum running async swap ops");
/*
* "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];
static uma_zone_t swap_zone;
static struct vm_object swap_zone_obj;
/*
* 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_putpages(vm_object_t, vm_page_t *, int, boolean_t, int *);
static boolean_t
swap_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before, int *after);
static void swap_pager_init(void);
static void swap_pager_unswapped(vm_page_t);
static void swap_pager_swapoff(struct swdevt *sp);
struct pagerops swappagerops = {
.pgo_init = swap_pager_init, /* early system initialization of pager */
.pgo_alloc = swap_pager_alloc, /* allocate an OBJT_SWAP object */
.pgo_dealloc = swap_pager_dealloc, /* deallocate an OBJT_SWAP object */
.pgo_getpages = swap_pager_getpages, /* pagein */
.pgo_putpages = swap_pager_putpages, /* pageout */
.pgo_haspage = swap_pager_haspage, /* get backing store status for page */
.pgo_pageunswapped = 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. dmmax is always a power of 2.
*
* swap_*() routines are externally accessible. swp_*() routines are
* internal.
*/
static int dmmax;
static int nswap_lowat = 128; /* in pages, swap_pager_almost_full warn */
static 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 void swp_sizecheck(void);
static void swp_pager_async_iodone(struct buf *bp);
static int swapongeom(struct thread *, struct vnode *);
static int swaponvp(struct thread *, struct vnode *, u_long);
/*
* Swap bitmap functions
*/
static void swp_pager_freeswapspace(daddr_t blk, int npages);
static daddr_t swp_pager_getswapspace(int npages);
/*
* Metadata functions
*/
static struct swblock **swp_pager_hash(vm_object_t object, vm_pindex_t index);
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 void
swp_sizecheck(void)
{
if (swap_pager_avail < 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 (swap_pager_avail > nswap_hiwat)
swap_pager_almost_full = 0;
}
}
/*
* SWP_PAGER_HASH() - hash swap meta data
*
* This is an 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 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);
}
/*
* 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(void)
{
/*
* Initialize object lists
*/
int i;
for (i = 0; i < NOBJLISTS; ++i)
TAILQ_INIT(&swap_pager_object_list[i]);
mtx_init(&sw_alloc_mtx, "swap_pager list", NULL, MTX_DEF);
mtx_init(&sw_dev_mtx, "swapdev", NULL, MTX_DEF);
/*
* Device Stripe, in PAGE_SIZE'd blocks
*/
dmmax = SWB_NPAGES * 2;
}
/*
* 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(void)
{
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 | UMA_ZONE_VM);
do {
if (uma_zone_set_obj(swap_zone, &swap_zone_obj, 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;
mtx_init(&swhash_mtx, "swap_pager swhash", NULL, MTX_DEF);
}
/*
* 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;
vm_pindex_t pindex;
pindex = OFF_TO_IDX(offset + PAGE_MASK + size);
if (handle) {
mtx_lock(&Giant);
/*
* 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, pindex);
object->handle = handle;
VM_OBJECT_LOCK(object);
swp_pager_meta_build(object, 0, SWAPBLK_NONE);
VM_OBJECT_UNLOCK(object);
}
sx_xunlock(&sw_alloc_sx);
mtx_unlock(&Giant);
} else {
object = vm_object_allocate(OBJT_DEFAULT, pindex);
VM_OBJECT_LOCK(object);
swp_pager_meta_build(object, 0, SWAPBLK_NONE);
VM_OBJECT_UNLOCK(object);
}
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(vm_object_t object)
{
int s;
/*
* Remove from list right away so lookups will fail if we block for
* pageout completion.
*/
if (object->handle != NULL) {
mtx_lock(&sw_alloc_mtx);
TAILQ_REMOVE(NOBJLIST(object->handle), object, pager_object_list);
mtx_unlock(&sw_alloc_mtx);
}
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
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().
*
* We allocate in round-robin fashion from the configured devices.
*/
static daddr_t
swp_pager_getswapspace(int npages)
{
daddr_t blk;
struct swdevt *sp;
int i;
blk = SWAPBLK_NONE;
mtx_lock(&sw_dev_mtx);
sp = swdevhd;
for (i = 0; i < nswapdev; i++) {
if (sp == NULL)
sp = TAILQ_FIRST(&swtailq);
if (!(sp->sw_flags & SW_CLOSING)) {
blk = blist_alloc(sp->sw_blist, npages);
if (blk != SWAPBLK_NONE) {
blk += sp->sw_first;
sp->sw_used += npages;
swap_pager_avail -= npages;
swp_sizecheck();
swdevhd = TAILQ_NEXT(sp, sw_list);
goto done;
}
}
sp = TAILQ_NEXT(sp, sw_list);
}
if (swap_pager_full != 2) {
printf("swap_pager_getswapspace(%d): failed\n", npages);
swap_pager_full = 2;
swap_pager_almost_full = 1;
}
swdevhd = NULL;
done:
mtx_unlock(&sw_dev_mtx);
return (blk);
}
static int
swp_pager_isondev(daddr_t blk, struct swdevt *sp)
{
return (blk >= sp->sw_first && blk < sp->sw_end);
}
static void
swp_pager_strategy(struct buf *bp)
{
struct swdevt *sp;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (bp->b_blkno >= sp->sw_first && bp->b_blkno < sp->sw_end) {
mtx_unlock(&sw_dev_mtx);
sp->sw_strategy(bp, sp);
return;
}
}
panic("Swapdev not found");
}
/*
* 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 void
swp_pager_freeswapspace(daddr_t blk, int npages)
{
struct swdevt *sp;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (blk >= sp->sw_first && blk < sp->sw_end) {
sp->sw_used -= npages;
/*
* If we are attempting to stop swapping on
* this device, we don't want to mark any
* blocks free lest they be reused.
*/
if ((sp->sw_flags & SW_CLOSING) == 0) {
blist_free(sp->sw_blist, blk - sp->sw_first,
npages);
swap_pager_avail += npages;
swp_sizecheck();
}
mtx_unlock(&sw_dev_mtx);
return;
}
}
panic("Swapdev not found");
}
/*
* 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(vm_object_t object, vm_pindex_t start, vm_size_t size)
{
int s = splvm();
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
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();
VM_OBJECT_LOCK(object);
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);
VM_OBJECT_UNLOCK(object);
splx(s);
return (-1);
}
}
}
swp_pager_meta_build(object, start, blk);
--size;
++start;
++blk;
--n;
}
swp_pager_meta_free(object, start, n);
VM_OBJECT_UNLOCK(object);
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(vm_object_t srcobject, vm_object_t dstobject,
vm_pindex_t offset, int destroysource)
{
vm_pindex_t i;
int s;
VM_OBJECT_LOCK_ASSERT(srcobject, MA_OWNED);
VM_OBJECT_LOCK_ASSERT(dstobject, MA_OWNED);
s = splvm();
/*
* If destroysource is set, we remove the source object from the
* swap_pager internal queue now.
*/
if (destroysource) {
if (srcobject->handle != NULL) {
mtx_lock(&sw_alloc_mtx);
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() can sleep.
*/
vm_object_pip_add(srcobject, 1);
VM_OBJECT_UNLOCK(srcobject);
vm_object_pip_add(dstobject, 1);
swp_pager_meta_build(dstobject, i, srcaddr);
vm_object_pip_wakeup(dstobject);
VM_OBJECT_LOCK(srcobject);
vm_object_pip_wakeup(srcobject);
}
} 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.
*/
static boolean_t
swap_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before, int *after)
{
daddr_t blk0;
int s;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
/*
* 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(vm_page_t m)
{
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
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(vm_object_t object, vm_page_t *m, int count, int reqpage)
{
struct buf *bp;
vm_page_t mreq;
int s;
int i;
int j;
daddr_t blk;
mreq = m[reqpage];
KASSERT(mreq->object == object,
("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 but we know it to
* not span devices. 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;
}
++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;
}
/*
* 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);
/*
* Getpbuf() can sleep.
*/
VM_OBJECT_UNLOCK(object);
/*
* Get a swap buffer header to perform the IO
*/
bp = getpbuf(&nsw_rcount);
bp->b_flags |= B_PAGING;
/*
* map our page(s) into kva for input
*/
pmap_qenter((vm_offset_t)bp->b_data, 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_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;
VM_OBJECT_LOCK(object);
vm_page_lock_queues();
{
int k;
for (k = i; k < j; ++k) {
bp->b_pages[k - i] = m[k];
vm_page_flag_set(m[k], PG_SWAPINPROG);
}
}
vm_page_unlock_queues();
VM_OBJECT_UNLOCK(object);
bp->b_npages = j - i;
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_LOCK(mreq->object);
vm_object_pip_add(mreq->object, bp->b_npages);
VM_OBJECT_UNLOCK(mreq->object);
/*
* 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 swapdev_strategy
*/
BUF_KERNPROC(bp);
swp_pager_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();
vm_page_lock_queues();
while ((mreq->flags & PG_SWAPINPROG) != 0) {
vm_page_flag_set(mreq, PG_WANTED | PG_REFERENCED);
cnt.v_intrans++;
if (msleep(mreq, &vm_page_queue_mtx, PSWP, "swread", hz*20)) {
printf(
"swap_pager: indefinite wait buffer: bufobj: %p, blkno: %jd, size: %ld\n",
bp->b_bufobj, (intmax_t)bp->b_blkno, bp->b_bcount);
}
}
vm_page_unlock_queues();
splx(s);
VM_OBJECT_LOCK(mreq->object);
/*
* 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(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);
VM_OBJECT_UNLOCK(object);
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;
}
/*
* All I/O parameters have been satisfied, build the I/O
* request and assign the swap space.
*/
if (sync == TRUE) {
bp = getpbuf(&nsw_wcount_sync);
} else {
bp = getpbuf(&nsw_wcount_async);
bp->b_flags = B_ASYNC;
}
bp->b_flags |= B_PAGING;
bp->b_iocmd = BIO_WRITE;
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;
VM_OBJECT_LOCK(object);
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_lock_queues();
vm_page_flag_set(mreq, PG_SWAPINPROG);
vm_page_unlock_queues();
bp->b_pages[j] = mreq;
}
VM_OBJECT_UNLOCK(object);
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;
splx(s);
/*
* asynchronous
*
* NOTE: b_blkno is destroyed by the call to swapdev_strategy
*/
if (sync == FALSE) {
bp->b_iodone = swp_pager_async_iodone;
BUF_KERNPROC(bp);
swp_pager_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 swapdev_strategy
*/
bp->b_iodone = bdone;
swp_pager_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();
bwait(bp, PVM, "swwrt");
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);
}
VM_OBJECT_LOCK(object);
}
/*
* 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(struct buf *bp)
{
int s;
int i;
vm_object_t object = NULL;
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().
*/
s = splvm();
/*
* remove the mapping for kernel virtual
*/
pmap_qremove((vm_offset_t)bp->b_data, bp->b_npages);
if (bp->b_npages) {
object = bp->b_pages[0]->object;
VM_OBJECT_LOCK(object);
}
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;
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.
*
* 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);
/*
* 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);
}
}
vm_page_unlock_queues();
/*
* adjust pip. NOTE: the original parent may still have its own
* pip refs on the object.
*/
if (object != NULL) {
vm_object_pip_wakeupn(object, bp->b_npages);
VM_OBJECT_UNLOCK(object);
}
/*
* 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_pager_isswapped:
*
* Return 1 if at least one page in the given object is paged
* out to the given swap device.
*
* This routine may not block.
*/
int
swap_pager_isswapped(vm_object_t object, struct swdevt *sp)
{
daddr_t index = 0;
int bcount;
int i;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
if (object->type != OBJT_SWAP)
return (0);
mtx_lock(&swhash_mtx);
for (bcount = 0; bcount < object->un_pager.swp.swp_bcount; bcount++) {
struct swblock *swap;
if ((swap = *swp_pager_hash(object, index)) != NULL) {
for (i = 0; i < SWAP_META_PAGES; ++i) {
if (swp_pager_isondev(swap->swb_pages[i], sp)) {
mtx_unlock(&swhash_mtx);
return (1);
}
}
}
index += SWAP_META_PAGES;
if (index > 0x20000000)
panic("swap_pager_isswapped: failed to locate all swap meta blocks");
}
mtx_unlock(&swhash_mtx);
return (0);
}
/*
* SWP_PAGER_FORCE_PAGEIN() - force a swap block to be paged in
*
* This routine dissociates the page at the given index within a
* swap block from its backing store, paging it in if necessary.
* If the page is paged in, it is placed in the inactive queue,
* since it had its backing store ripped out from under it.
* We also attempt to swap in all other pages in the swap block,
* we only guarantee that the one at the specified index is
* paged in.
*
* XXX - The code to page the whole block in doesn't work, so we
* revert to the one-by-one behavior for now. Sigh.
*/
static __inline void
swp_pager_force_pagein(vm_object_t object, vm_pindex_t pindex)
{
vm_page_t m;
vm_object_pip_add(object, 1);
m = vm_page_grab(object, pindex, VM_ALLOC_NORMAL|VM_ALLOC_RETRY);
if (m->valid == VM_PAGE_BITS_ALL) {
vm_object_pip_subtract(object, 1);
vm_page_lock_queues();
vm_page_activate(m);
vm_page_dirty(m);
vm_page_wakeup(m);
vm_page_unlock_queues();
vm_pager_page_unswapped(m);
return;
}
if (swap_pager_getpages(object, &m, 1, 0) != VM_PAGER_OK)
panic("swap_pager_force_pagein: read from swap failed");/*XXX*/
vm_object_pip_subtract(object, 1);
vm_page_lock_queues();
vm_page_dirty(m);
vm_page_dontneed(m);
vm_page_wakeup(m);
vm_page_unlock_queues();
vm_pager_page_unswapped(m);
}
/*
* swap_pager_swapoff:
*
* Page in all of the pages that have been paged out to the
* given device. The corresponding blocks in the bitmap must be
* marked as allocated and the device must be flagged SW_CLOSING.
* There may be no processes swapped out to the device.
*
* This routine may block.
*/
static void
swap_pager_swapoff(struct swdevt *sp)
{
struct swblock *swap;
int i, j, retries;
GIANT_REQUIRED;
retries = 0;
full_rescan:
mtx_lock(&swhash_mtx);
for (i = 0; i <= swhash_mask; i++) { /* '<=' is correct here */
restart:
for (swap = swhash[i]; swap != NULL; swap = swap->swb_hnext) {
vm_object_t object = swap->swb_object;
vm_pindex_t pindex = swap->swb_index;
for (j = 0; j < SWAP_META_PAGES; ++j) {
if (swp_pager_isondev(swap->swb_pages[j], sp)) {
/* avoid deadlock */
if (!VM_OBJECT_TRYLOCK(object)) {
break;
} else {
mtx_unlock(&swhash_mtx);
swp_pager_force_pagein(object,
pindex + j);
VM_OBJECT_UNLOCK(object);
mtx_lock(&swhash_mtx);
goto restart;
}
}
}
}
}
mtx_unlock(&swhash_mtx);
if (sp->sw_used) {
int dummy;
/*
* Objects may be locked or paging to the device being
* removed, so we will miss their pages and need to
* make another pass. We have marked this device as
* SW_CLOSING, so the activity should finish soon.
*/
retries++;
if (retries > 100) {
panic("swapoff: failed to locate %d swap blocks",
sp->sw_used);
}
tsleep(&dummy, PVM, "swpoff", hz / 20);
goto full_rescan;
}
}
/************************************************************************
* 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_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;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
/*
* 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) {
mtx_lock(&sw_alloc_mtx);
TAILQ_INSERT_TAIL(
NOBJLIST(object->handle),
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:
mtx_lock(&swhash_mtx);
pswap = swp_pager_hash(object, pindex);
if ((swap = *pswap) == NULL) {
int i;
if (swapblk == SWAPBLK_NONE)
goto done;
swap = *pswap = uma_zalloc(swap_zone, M_NOWAIT);
if (swap == NULL) {
mtx_unlock(&swhash_mtx);
VM_OBJECT_UNLOCK(object);
VM_WAIT;
VM_OBJECT_LOCK(object);
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;
done:
mtx_unlock(&swhash_mtx);
}
/*
* 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)
{
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
if (object->type != OBJT_SWAP)
return;
while (count > 0) {
struct swblock **pswap;
struct swblock *swap;
mtx_lock(&swhash_mtx);
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;
}
mtx_unlock(&swhash_mtx);
}
}
/*
* 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;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
if (object->type != OBJT_SWAP)
return;
while (object->un_pager.swp.swp_bcount) {
struct swblock **pswap;
struct swblock *swap;
mtx_lock(&swhash_mtx);
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;
}
mtx_unlock(&swhash_mtx);
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;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
/*
* 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;
mtx_lock(&swhash_mtx);
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;
}
}
}
}
mtx_unlock(&swhash_mtx);
return (r1);
}
/*
* System call swapon(name) enables swapping on device name,
* which must be in the swdevsw. Return EBUSY
* if already swapping on this device.
*/
#ifndef _SYS_SYSPROTO_H_
struct swapon_args {
char *name;
};
#endif
/*
* MPSAFE
*/
/* ARGSUSED */
int
swapon(struct thread *td, struct swapon_args *uap)
{
struct vattr attr;
struct vnode *vp;
struct nameidata nd;
int error;
mtx_lock(&Giant);
error = suser(td);
if (error)
goto done2;
while (swdev_syscall_active)
tsleep(&swdev_syscall_active, PUSER - 1, "swpon", 0);
swdev_syscall_active = 1;
/*
* Swap metadata may not fit in the KVM if we have physical
* memory of >1GB.
*/
if (swap_zone == NULL) {
error = ENOMEM;
goto done;
}
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, uap->name, td);
error = namei(&nd);
if (error)
goto done;
NDFREE(&nd, NDF_ONLY_PNBUF);
vp = nd.ni_vp;
if (vn_isdisk(vp, &error)) {
error = swapongeom(td, vp);
} else if (vp->v_type == VREG &&
(vp->v_mount->mnt_vfc->vfc_flags & VFCF_NETWORK) != 0 &&
(error = VOP_GETATTR(vp, &attr, td->td_ucred, td)) == 0) {
/*
* Allow direct swapping to NFS regular files in the same
* way that nfs_mountroot() sets up diskless swapping.
*/
error = swaponvp(td, vp, attr.va_size / DEV_BSIZE);
}
if (error)
vrele(vp);
done:
swdev_syscall_active = 0;
wakeup_one(&swdev_syscall_active);
done2:
mtx_unlock(&Giant);
return (error);
}
static void
swaponsomething(struct vnode *vp, void *id, u_long nblks, sw_strategy_t *strategy, sw_close_t *close, dev_t dev)
{
struct swdevt *sp, *tsp;
swblk_t dvbase;
u_long mblocks;
/*
* If we go beyond this, we get overflows in the radix
* tree bitmap code.
*/
mblocks = 0x40000000 / BLIST_META_RADIX;
if (nblks > mblocks) {
printf("WARNING: reducing size to maximum of %lu blocks per swap unit\n",
mblocks);
nblks = mblocks;
}
/*
* nblks is in DEV_BSIZE'd chunks, convert to PAGE_SIZE'd chunks.
* First chop nblks off to page-align it, then convert.
*
* sw->sw_nblks is in page-sized chunks now too.
*/
nblks &= ~(ctodb(1) - 1);
nblks = dbtoc(nblks);
sp = malloc(sizeof *sp, M_VMPGDATA, M_WAITOK | M_ZERO);
sp->sw_vp = vp;
sp->sw_id = id;
sp->sw_dev = dev;
sp->sw_flags = 0;
sp->sw_nblks = nblks;
sp->sw_used = 0;
sp->sw_strategy = strategy;
sp->sw_close = close;
sp->sw_blist = blist_create(nblks);
/*
* Do not free the first two block in order to avoid overwriting
* any bsd label at the front of the partition
*/
blist_free(sp->sw_blist, 2, nblks - 2);
dvbase = 0;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(tsp, &swtailq, sw_list) {
if (tsp->sw_end >= dvbase) {
/*
* We put one uncovered page between the devices
* in order to definitively prevent any cross-device
* I/O requests
*/
dvbase = tsp->sw_end + 1;
}
}
sp->sw_first = dvbase;
sp->sw_end = dvbase + nblks;
TAILQ_INSERT_TAIL(&swtailq, sp, sw_list);
nswapdev++;
swap_pager_avail += nblks;
swp_sizecheck();
mtx_unlock(&sw_dev_mtx);
}
/*
* SYSCALL: swapoff(devname)
*
* Disable swapping on the given device.
*
* XXX: Badly designed system call: it should use a device index
* rather than filename as specification. We keep sw_vp around
* only to make this work.
*/
#ifndef _SYS_SYSPROTO_H_
struct swapoff_args {
char *name;
};
#endif
/*
* MPSAFE
*/
/* ARGSUSED */
int
swapoff(struct thread *td, struct swapoff_args *uap)
{
struct vnode *vp;
struct nameidata nd;
struct swdevt *sp;
u_long nblks, dvbase;
int error;
mtx_lock(&Giant);
error = suser(td);
if (error)
goto done2;
while (swdev_syscall_active)
tsleep(&swdev_syscall_active, PUSER - 1, "swpoff", 0);
swdev_syscall_active = 1;
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, uap->name, td);
error = namei(&nd);
if (error)
goto done;
NDFREE(&nd, NDF_ONLY_PNBUF);
vp = nd.ni_vp;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (sp->sw_vp == vp)
goto found;
}
mtx_unlock(&sw_dev_mtx);
error = EINVAL;
goto done;
found:
mtx_unlock(&sw_dev_mtx);
#ifdef MAC
(void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
error = mac_check_system_swapoff(td->td_ucred, vp);
(void) VOP_UNLOCK(vp, 0, td);
if (error != 0)
goto done;
#endif
nblks = sp->sw_nblks;
/*
* We can turn off this swap device safely only if the
* available virtual memory in the system will fit the amount
* of data we will have to page back in, plus an epsilon so
* the system doesn't become critically low on swap space.
*/
if (cnt.v_free_count + cnt.v_cache_count + swap_pager_avail <
nblks + nswap_lowat) {
error = ENOMEM;
goto done;
}
/*
* Prevent further allocations on this device.
*/
mtx_lock(&sw_dev_mtx);
sp->sw_flags |= SW_CLOSING;
for (dvbase = 0; dvbase < sp->sw_end; dvbase += dmmax) {
swap_pager_avail -= blist_fill(sp->sw_blist,
dvbase, dmmax);
}
mtx_unlock(&sw_dev_mtx);
/*
* Page in the contents of the device and close it.
*/
swap_pager_swapoff(sp);
sp->sw_close(td, sp);
sp->sw_id = NULL;
mtx_lock(&sw_dev_mtx);
TAILQ_REMOVE(&swtailq, sp, sw_list);
nswapdev--;
if (nswapdev == 0) {
swap_pager_full = 2;
swap_pager_almost_full = 1;
}
if (swdevhd == sp)
swdevhd = NULL;
mtx_unlock(&sw_dev_mtx);
blist_destroy(sp->sw_blist);
free(sp, M_VMPGDATA);
done:
swdev_syscall_active = 0;
wakeup_one(&swdev_syscall_active);
done2:
mtx_unlock(&Giant);
return (error);
}
void
swap_pager_status(int *total, int *used)
{
struct swdevt *sp;
*total = 0;
*used = 0;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
*total += sp->sw_nblks;
*used += sp->sw_used;
}
mtx_unlock(&sw_dev_mtx);
}
static int
sysctl_vm_swap_info(SYSCTL_HANDLER_ARGS)
{
int *name = (int *)arg1;
int error, n;
struct xswdev xs;
struct swdevt *sp;
if (arg2 != 1) /* name length */
return (EINVAL);
n = 0;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (n == *name) {
mtx_unlock(&sw_dev_mtx);
xs.xsw_version = XSWDEV_VERSION;
xs.xsw_dev = sp->sw_dev;
xs.xsw_flags = sp->sw_flags;
xs.xsw_nblks = sp->sw_nblks;
xs.xsw_used = sp->sw_used;
error = SYSCTL_OUT(req, &xs, sizeof(xs));
return (error);
}
n++;
}
mtx_unlock(&sw_dev_mtx);
return (ENOENT);
}
SYSCTL_INT(_vm, OID_AUTO, nswapdev, CTLFLAG_RD, &nswapdev, 0,
"Number of swap devices");
SYSCTL_NODE(_vm, OID_AUTO, swap_info, CTLFLAG_RD, sysctl_vm_swap_info,
"Swap statistics by device");
/*
* vmspace_swap_count() - count the approximate swap useage in pages for a
* vmspace.
*
* The map must be locked.
*
* Swap useage is determined by taking the proportional swap used by
* VM objects backing the VM map. To make up for fractional losses,
* if the VM object has any swap use at all the associated map entries
* count for at least 1 swap page.
*/
int
vmspace_swap_count(struct vmspace *vmspace)
{
vm_map_t map = &vmspace->vm_map;
vm_map_entry_t cur;
int count = 0;
for (cur = map->header.next; cur != &map->header; cur = cur->next) {
vm_object_t object;
if ((cur->eflags & MAP_ENTRY_IS_SUB_MAP) == 0 &&
(object = cur->object.vm_object) != NULL) {
VM_OBJECT_LOCK(object);
if (object->type == OBJT_SWAP &&
object->un_pager.swp.swp_bcount != 0) {
int n = (cur->end - cur->start) / PAGE_SIZE;
count += object->un_pager.swp.swp_bcount *
SWAP_META_PAGES * n / object->size + 1;
}
VM_OBJECT_UNLOCK(object);
}
}
return (count);
}
/*
* GEOM backend
*
* Swapping onto disk devices.
*
*/
static g_orphan_t swapgeom_orphan;
static struct g_class g_swap_class = {
.name = "SWAP",
.version = G_VERSION,
.orphan = swapgeom_orphan,
};
DECLARE_GEOM_CLASS(g_swap_class, g_class);
static void
swapgeom_done(struct bio *bp2)
{
struct buf *bp;
bp = bp2->bio_caller2;
bp->b_ioflags = bp2->bio_flags;
if (bp2->bio_error)
bp->b_ioflags |= BIO_ERROR;
bp->b_resid = bp->b_bcount - bp2->bio_completed;
bp->b_error = bp2->bio_error;
bufdone(bp);
g_destroy_bio(bp2);
}
static void
swapgeom_strategy(struct buf *bp, struct swdevt *sp)
{
struct bio *bio;
struct g_consumer *cp;
cp = sp->sw_id;
if (cp == NULL) {
bp->b_error = ENXIO;
bp->b_ioflags |= BIO_ERROR;
bufdone(bp);
return;
}
bio = g_alloc_bio();
#if 0
/*
* XXX: We shouldn't really sleep here when we run out of buffers
* XXX: but the alternative is worse right now.
*/
if (bio == NULL) {
bp->b_error = ENOMEM;
bp->b_ioflags |= BIO_ERROR;
bufdone(bp);
return;
}
#endif
bio->bio_caller2 = bp;
bio->bio_cmd = bp->b_iocmd;
bio->bio_data = bp->b_data;
bio->bio_offset = (bp->b_blkno - sp->sw_first) * PAGE_SIZE;
bio->bio_length = bp->b_bcount;
bio->bio_done = swapgeom_done;
g_io_request(bio, cp);
return;
}
static void
swapgeom_orphan(struct g_consumer *cp)
{
struct swdevt *sp;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list)
if (sp->sw_id == cp)
sp->sw_id = NULL;
mtx_unlock(&sw_dev_mtx);
}
static void
swapgeom_close_ev(void *arg, int flags)
{
struct g_consumer *cp;
cp = arg;
g_access(cp, -1, -1, 0);
g_detach(cp);
g_destroy_consumer(cp);
}
static void
swapgeom_close(struct thread *td, struct swdevt *sw)
{
/* XXX: direct call when Giant untangled */
g_waitfor_event(swapgeom_close_ev, sw->sw_id, M_WAITOK, NULL);
}
struct swh0h0 {
struct cdev *dev;
struct vnode *vp;
int error;
};
static void
swapongeom_ev(void *arg, int flags)
{
struct swh0h0 *swh;
struct g_provider *pp;
struct g_consumer *cp;
static struct g_geom *gp;
struct swdevt *sp;
u_long nblks;
int error;
swh = arg;
swh->error = 0;
pp = g_dev_getprovider(swh->dev);
if (pp == NULL) {
swh->error = ENODEV;
return;
}
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
cp = sp->sw_id;
if (cp != NULL && cp->provider == pp) {
mtx_unlock(&sw_dev_mtx);
swh->error = EBUSY;
return;
}
}
mtx_unlock(&sw_dev_mtx);
if (gp == NULL)
gp = g_new_geomf(&g_swap_class, "swap", NULL);
cp = g_new_consumer(gp);
g_attach(cp, pp);
/*
* XXX: Everytime you think you can improve the margin for
* footshooting, somebody depends on the ability to do so:
* savecore(8) wants to write to our swapdev so we cannot
* set an exclusive count :-(
*/
error = g_access(cp, 1, 1, 0);
if (error) {
g_detach(cp);
g_destroy_consumer(cp);
swh->error = error;
return;
}
nblks = pp->mediasize / DEV_BSIZE;
swaponsomething(swh->vp, cp, nblks, swapgeom_strategy,
swapgeom_close, dev2udev(swh->dev));
swh->error = 0;
return;
}
static int
swapongeom(struct thread *td, struct vnode *vp)
{
int error;
struct swh0h0 swh;
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
swh.dev = vp->v_rdev;
swh.vp = vp;
swh.error = 0;
/* XXX: direct call when Giant untangled */
error = g_waitfor_event(swapongeom_ev, &swh, M_WAITOK, NULL);
if (!error)
error = swh.error;
VOP_UNLOCK(vp, 0, td);
return (error);
}
/*
* VNODE backend
*
* This is used mainly for network filesystem (read: probably only tested
* with NFS) swapfiles.
*
*/
static void
swapdev_strategy(struct buf *bp, struct swdevt *sp)
{
int s;
struct vnode *vp2;
bp->b_blkno = ctodb(bp->b_blkno - sp->sw_first);
vp2 = sp->sw_id;
vhold(vp2);
s = splvm();
if (bp->b_iocmd == BIO_WRITE) {
if (bp->b_bufobj) /* XXX: should always be true /phk */
bufobj_wdrop(bp->b_bufobj);
bufobj_wref(&vp2->v_bufobj);
}
bp->b_vp = vp2;
splx(s);
bp->b_iooffset = dbtob(bp->b_blkno);
bstrategy(bp);
return;
}
static void
swapdev_close(struct thread *td, struct swdevt *sp)
{
VOP_CLOSE(sp->sw_vp, FREAD | FWRITE, td->td_ucred, td);
vrele(sp->sw_vp);
}
static int
swaponvp(struct thread *td, struct vnode *vp, u_long nblks)
{
struct swdevt *sp;
int error;
if (nblks == 0)
return (ENXIO);
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (sp->sw_id == vp) {
mtx_unlock(&sw_dev_mtx);
return (EBUSY);
}
}
mtx_unlock(&sw_dev_mtx);
(void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
#ifdef MAC
error = mac_check_system_swapon(td->td_ucred, vp);
if (error == 0)
#endif
error = VOP_OPEN(vp, FREAD | FWRITE, td->td_ucred, td, -1);
(void) VOP_UNLOCK(vp, 0, td);
if (error)
return (error);
swaponsomething(vp, vp, nblks, swapdev_strategy, swapdev_close,
NODEV);
return (0);
}
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