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freebsd/sys/vm/swap_pager.c
Alan Cox 5a32489377 Make vm_page's PG_ZERO flag immutable between the time of the page's 
allocation and deallocation.  This flag's principal use is shortly after
allocation.  For such cases, clearing the flag is pointless.  The only
unusual use of PG_ZERO is in vfs_bio_clrbuf().  However, allocbuf() never
requests a prezeroed page.  So, vfs_bio_clrbuf() never sees a prezeroed
page.

Reviewed by:	tegge@
2004-05-06 05:03:23 +00:00

2604 lines
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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;
udev_t sw_udev;
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;
/*
* 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, int *sw_used);
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, 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;
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 struct swdevt *
swp_pager_find_dev(daddr_t blk)
{
struct swdevt *sp;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (blk >= sp->sw_first && blk < sp->sw_end) {
mtx_unlock(&sw_dev_mtx);
return (sp);
}
}
panic("Swapdev not found");
}
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: device:"
" %s, blkno: %ld, size: %ld\n",
devtoname(bp->b_dev), (long)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);
for (bcount = 0; bcount < object->un_pager.swp.swp_bcount; bcount++) {
struct swblock *swap;
mtx_lock(&swhash_mtx);
if ((swap = *swp_pager_hash(object, index)) != NULL) {
for (i = 0; i < SWAP_META_PAGES; ++i) {
daddr_t v = swap->swb_pages[i];
if (v == SWAPBLK_NONE)
continue;
if (swp_pager_find_dev(v) == sp) {
mtx_unlock(&swhash_mtx);
return 1;
}
}
}
mtx_unlock(&swhash_mtx);
index += SWAP_META_PAGES;
if (index > 0x20000000)
panic("swap_pager_isswapped: failed to locate all swap meta blocks");
}
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(struct swblock *swap, int idx)
{
vm_object_t object;
vm_page_t m;
vm_pindex_t pindex;
object = swap->swb_object;
pindex = swap->swb_index;
mtx_unlock(&swhash_mtx);
VM_OBJECT_LOCK(object);
vm_object_pip_add(object, 1);
m = vm_page_grab(object, pindex + idx, 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);
VM_OBJECT_UNLOCK(object);
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);
VM_OBJECT_UNLOCK(object);
}
/*
* 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.
*
* The sw_used parameter points to the field in the swdev structure
* that contains a count of the number of blocks still allocated
* on the device. If we encounter objects with a nonzero pip count
* in our scan, we use this number to determine if we're really done.
*
* This routine may block.
*/
static void
swap_pager_swapoff(struct swdevt *sp, int *sw_used)
{
struct swblock **pswap;
struct swblock *swap;
vm_object_t waitobj;
daddr_t v;
int i, j;
GIANT_REQUIRED;
full_rescan:
waitobj = NULL;
for (i = 0; i <= swhash_mask; i++) { /* '<=' is correct here */
restart:
pswap = &swhash[i];
mtx_lock(&swhash_mtx);
while ((swap = *pswap) != NULL) {
for (j = 0; j < SWAP_META_PAGES; ++j) {
v = swap->swb_pages[j];
if (v != SWAPBLK_NONE &&
swp_pager_find_dev(v) == sp)
break;
}
if (j < SWAP_META_PAGES) {
swp_pager_force_pagein(swap, j);
goto restart;
} else if (swap->swb_object->paging_in_progress) {
if (!waitobj)
waitobj = swap->swb_object;
}
pswap = &swap->swb_hnext;
}
mtx_unlock(&swhash_mtx);
}
if (waitobj && *sw_used) {
/*
* We wait on an arbitrary object to clock our rescans
* to the rate of paging completion.
*/
VM_OBJECT_LOCK(waitobj);
vm_object_pip_wait(waitobj, "swpoff");
VM_OBJECT_UNLOCK(waitobj);
goto full_rescan;
}
if (*sw_used)
panic("swapoff: failed to locate %d swap blocks", *sw_used);
}
/************************************************************************
* 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, udev_t udev)
{
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_udev = udev;
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.
*/
#ifndef NO_SWAPPING
vm_proc_swapin_all(sp);
#endif /* !NO_SWAPPING */
swap_pager_swapoff(sp, &sp->sw_used);
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_udev;
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 struct g_class g_swap_class = {
.name = "SWAP",
};
DECLARE_GEOM_CLASS(g_swap_class, g_class);
static void
swapgeom_done(struct bio *bp2)
{
struct buf *bp;
bp = bp2->bio_caller2;
if (bp2->bio_error)
bp->b_ioflags |= 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_clone_bio(&bp->b_io);
if (bio == NULL) {
/*
* XXX: This is better than panicing, but not much better.
* XXX: Somehow this should be retried. A more generic
* XXX: implementation of ENOMEM in geom may be able to cope.
*/
bp->b_error = ENOMEM;
bp->b_ioflags |= BIO_ERROR;
bufdone(bp);
return;
}
bio->bio_caller2 = bp;
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 {
dev_t 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);
gp->orphan = swapgeom_orphan;
}
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 *vp, *vp2;
bp->b_dev = NODEV;
bp->b_blkno = ctodb(bp->b_blkno - sp->sw_first);
vp2 = sp->sw_id;
vhold(vp2);
s = splvm();
if (bp->b_iocmd == BIO_WRITE) {
vp = bp->b_vp;
if (vp) {
VI_LOCK(vp);
vp->v_numoutput--;
if ((vp->v_iflag & VI_BWAIT) && vp->v_numoutput <= 0) {
vp->v_iflag &= ~VI_BWAIT;
wakeup(&vp->v_numoutput);
}
VI_UNLOCK(vp);
}
VI_LOCK(vp2);
vp2->v_numoutput++;
VI_UNLOCK(vp2);
}
bp->b_vp = vp2;
splx(s);
bp->b_iooffset = dbtob(bp->b_blkno);
VOP_STRATEGY(vp2, 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,
NOUDEV);
return (0);
}
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