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freebsd-skq/sys/vm/swap_pager.c
Konstantin Belousov cd85379104 Make MAXPHYS tunable. Bump MAXPHYS to 1M. 
Replace MAXPHYS by runtime variable maxphys. It is initialized from
MAXPHYS by default, but can be also adjusted with the tunable kern.maxphys.

Make b_pages[] array in struct buf flexible.  Size b_pages[] for buffer
cache buffers exactly to atop(maxbcachebuf) (currently it is sized to
atop(MAXPHYS)), and b_pages[] for pbufs is sized to atop(maxphys) + 1.
The +1 for pbufs allow several pbuf consumers, among them vmapbuf(),
to use unaligned buffers still sized to maxphys, esp. when such
buffers come from userspace (*).  Overall, we save significant amount
of otherwise wasted memory in b_pages[] for buffer cache buffers,
while bumping MAXPHYS to desired high value.

Eliminate all direct uses of the MAXPHYS constant in kernel and driver
sources, except a place which initialize maxphys.  Some random (and
arguably weird) uses of MAXPHYS, e.g. in linuxolator, are converted
straight.  Some drivers, which use MAXPHYS to size embeded structures,
get private MAXPHYS-like constant; their convertion is out of scope
for this work.

Changes to cam/, dev/ahci, dev/ata, dev/mpr, dev/mpt, dev/mvs,
dev/siis, where either submitted by, or based on changes by mav.

Suggested by: mav (*)
Reviewed by:	imp, mav, imp, mckusick, scottl (intermediate versions)
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
Differential revision:	https://reviews.freebsd.org/D27225
2020-11-28 12:12:51 +00:00

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/*-
* SPDX-License-Identifier: BSD-4-Clause
*
* 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_vm.h"
#include <sys/param.h>
#include <sys/bio.h>
#include <sys/blist.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/disk.h>
#include <sys/disklabel.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/lock.h>
#include <sys/kernel.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/malloc.h>
#include <sys/pctrie.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/racct.h>
#include <sys/resource.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/sbuf.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/systm.h>
#include <sys/sx.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>
#include <security/mac/mac_framework.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>
/*
* MAX_PAGEOUT_CLUSTER must be a power of 2 between 1 and 64.
* The 64-page limit is due to the radix code (kern/subr_blist.c).
*/
#ifndef MAX_PAGEOUT_CLUSTER
#define MAX_PAGEOUT_CLUSTER 32
#endif
#if !defined(SWB_NPAGES)
#define SWB_NPAGES MAX_PAGEOUT_CLUSTER
#endif
#define SWAP_META_PAGES PCTRIE_COUNT
/*
* A swblk structure maps each page index within a
* SWAP_META_PAGES-aligned and sized range to the address of an
* on-disk swap block (or SWAPBLK_NONE). The collection of these
* mappings for an entire vm object is implemented as a pc-trie.
*/
struct swblk {
vm_pindex_t p;
daddr_t d[SWAP_META_PAGES];
};
static MALLOC_DEFINE(M_VMPGDATA, "vm_pgdata", "swap pager private data");
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 struct sx swdev_syscall_lock; /* serialize swap(on|off) */
static __exclusive_cache_line u_long swap_reserved;
static u_long swap_total;
static int sysctl_page_shift(SYSCTL_HANDLER_ARGS);
static SYSCTL_NODE(_vm_stats, OID_AUTO, swap, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
"VM swap stats");
SYSCTL_PROC(_vm, OID_AUTO, swap_reserved, CTLTYPE_U64 | CTLFLAG_RD | CTLFLAG_MPSAFE,
&swap_reserved, 0, sysctl_page_shift, "A",
"Amount of swap storage needed to back all allocated anonymous memory.");
SYSCTL_PROC(_vm, OID_AUTO, swap_total, CTLTYPE_U64 | CTLFLAG_RD | CTLFLAG_MPSAFE,
&swap_total, 0, sysctl_page_shift, "A",
"Total amount of available swap storage.");
static int overcommit = 0;
SYSCTL_INT(_vm, VM_OVERCOMMIT, overcommit, CTLFLAG_RW, &overcommit, 0,
"Configure virtual memory overcommit behavior. See tuning(7) "
"for details.");
static unsigned long swzone;
SYSCTL_ULONG(_vm, OID_AUTO, swzone, CTLFLAG_RD, &swzone, 0,
"Actual size of swap metadata zone");
static unsigned long swap_maxpages;
SYSCTL_ULONG(_vm, OID_AUTO, swap_maxpages, CTLFLAG_RD, &swap_maxpages, 0,
"Maximum amount of swap supported");
static COUNTER_U64_DEFINE_EARLY(swap_free_deferred);
SYSCTL_COUNTER_U64(_vm_stats_swap, OID_AUTO, free_deferred,
CTLFLAG_RD, &swap_free_deferred,
"Number of pages that deferred freeing swap space");
static COUNTER_U64_DEFINE_EARLY(swap_free_completed);
SYSCTL_COUNTER_U64(_vm_stats_swap, OID_AUTO, free_completed,
CTLFLAG_RD, &swap_free_completed,
"Number of deferred frees completed");
/* bits from overcommit */
#define SWAP_RESERVE_FORCE_ON (1 << 0)
#define SWAP_RESERVE_RLIMIT_ON (1 << 1)
#define SWAP_RESERVE_ALLOW_NONWIRED (1 << 2)
static int
sysctl_page_shift(SYSCTL_HANDLER_ARGS)
{
uint64_t newval;
u_long value = *(u_long *)arg1;
newval = ((uint64_t)value) << PAGE_SHIFT;
return (sysctl_handle_64(oidp, &newval, 0, req));
}
static bool
swap_reserve_by_cred_rlimit(u_long pincr, struct ucred *cred, int oc)
{
struct uidinfo *uip;
u_long prev;
uip = cred->cr_ruidinfo;
prev = atomic_fetchadd_long(&uip->ui_vmsize, pincr);
if ((oc & SWAP_RESERVE_RLIMIT_ON) != 0 &&
prev + pincr > lim_cur(curthread, RLIMIT_SWAP) &&
priv_check(curthread, PRIV_VM_SWAP_NORLIMIT) != 0) {
prev = atomic_fetchadd_long(&uip->ui_vmsize, -pincr);
KASSERT(prev >= pincr, ("negative vmsize for uid = %d\n", uip->ui_uid));
return (false);
}
return (true);
}
static void
swap_release_by_cred_rlimit(u_long pdecr, struct ucred *cred)
{
struct uidinfo *uip;
#ifdef INVARIANTS
u_long prev;
#endif
uip = cred->cr_ruidinfo;
#ifdef INVARIANTS
prev = atomic_fetchadd_long(&uip->ui_vmsize, -pdecr);
KASSERT(prev >= pdecr, ("negative vmsize for uid = %d\n", uip->ui_uid));
#else
atomic_subtract_long(&uip->ui_vmsize, pdecr);
#endif
}
static void
swap_reserve_force_rlimit(u_long pincr, struct ucred *cred)
{
struct uidinfo *uip;
uip = cred->cr_ruidinfo;
atomic_add_long(&uip->ui_vmsize, pincr);
}
bool
swap_reserve(vm_ooffset_t incr)
{
return (swap_reserve_by_cred(incr, curthread->td_ucred));
}
bool
swap_reserve_by_cred(vm_ooffset_t incr, struct ucred *cred)
{
u_long r, s, prev, pincr;
#ifdef RACCT
int error;
#endif
int oc;
static int curfail;
static struct timeval lastfail;
KASSERT((incr & PAGE_MASK) == 0, ("%s: incr: %ju & PAGE_MASK", __func__,
(uintmax_t)incr));
#ifdef RACCT
if (RACCT_ENABLED()) {
PROC_LOCK(curproc);
error = racct_add(curproc, RACCT_SWAP, incr);
PROC_UNLOCK(curproc);
if (error != 0)
return (false);
}
#endif
pincr = atop(incr);
prev = atomic_fetchadd_long(&swap_reserved, pincr);
r = prev + pincr;
s = swap_total;
oc = atomic_load_int(&overcommit);
if (r > s && (oc & SWAP_RESERVE_ALLOW_NONWIRED) != 0) {
s += vm_cnt.v_page_count - vm_cnt.v_free_reserved -
vm_wire_count();
}
if ((oc & SWAP_RESERVE_FORCE_ON) != 0 && r > s &&
priv_check(curthread, PRIV_VM_SWAP_NOQUOTA) != 0) {
prev = atomic_fetchadd_long(&swap_reserved, -pincr);
KASSERT(prev >= pincr, ("swap_reserved < incr on overcommit fail"));
goto out_error;
}
if (!swap_reserve_by_cred_rlimit(pincr, cred, oc)) {
prev = atomic_fetchadd_long(&swap_reserved, -pincr);
KASSERT(prev >= pincr, ("swap_reserved < incr on overcommit fail"));
goto out_error;
}
return (true);
out_error:
if (ppsratecheck(&lastfail, &curfail, 1)) {
printf("uid %d, pid %d: swap reservation for %jd bytes failed\n",
cred->cr_ruidinfo->ui_uid, curproc->p_pid, incr);
}
#ifdef RACCT
if (RACCT_ENABLED()) {
PROC_LOCK(curproc);
racct_sub(curproc, RACCT_SWAP, incr);
PROC_UNLOCK(curproc);
}
#endif
return (false);
}
void
swap_reserve_force(vm_ooffset_t incr)
{
u_long pincr;
KASSERT((incr & PAGE_MASK) == 0, ("%s: incr: %ju & PAGE_MASK", __func__,
(uintmax_t)incr));
#ifdef RACCT
if (RACCT_ENABLED()) {
PROC_LOCK(curproc);
racct_add_force(curproc, RACCT_SWAP, incr);
PROC_UNLOCK(curproc);
}
#endif
pincr = atop(incr);
atomic_add_long(&swap_reserved, pincr);
swap_reserve_force_rlimit(pincr, curthread->td_ucred);
}
void
swap_release(vm_ooffset_t decr)
{
struct ucred *cred;
PROC_LOCK(curproc);
cred = curproc->p_ucred;
swap_release_by_cred(decr, cred);
PROC_UNLOCK(curproc);
}
void
swap_release_by_cred(vm_ooffset_t decr, struct ucred *cred)
{
u_long pdecr;
#ifdef INVARIANTS
u_long prev;
#endif
KASSERT((decr & PAGE_MASK) == 0, ("%s: decr: %ju & PAGE_MASK", __func__,
(uintmax_t)decr));
pdecr = atop(decr);
#ifdef INVARIANTS
prev = atomic_fetchadd_long(&swap_reserved, -pdecr);
KASSERT(prev >= pdecr, ("swap_reserved < decr"));
#else
atomic_subtract_long(&swap_reserved, pdecr);
#endif
swap_release_by_cred_rlimit(pdecr, cred);
#ifdef RACCT
if (racct_enable)
racct_sub_cred(cred, RACCT_SWAP, decr);
#endif
}
static int swap_pager_full = 2; /* swap space exhaustion (task killing) */
static int swap_pager_almost_full = 1; /* swap space exhaustion (w/hysteresis)*/
static struct mtx swbuf_mtx; /* to sync nsw_wcount_async */
static int nsw_wcount_async; /* limit async write buffers */
static int nsw_wcount_async_max;/* assigned maximum */
static int nsw_cluster_max; /* maximum VOP I/O allowed */
static int sysctl_swap_async_max(SYSCTL_HANDLER_ARGS);
SYSCTL_PROC(_vm, OID_AUTO, swap_async_max, CTLTYPE_INT | CTLFLAG_RW |
CTLFLAG_MPSAFE, NULL, 0, sysctl_swap_async_max, "I",
"Maximum running async swap ops");
static int sysctl_swap_fragmentation(SYSCTL_HANDLER_ARGS);
SYSCTL_PROC(_vm, OID_AUTO, swap_fragmentation, CTLTYPE_STRING | CTLFLAG_RD |
CTLFLAG_MPSAFE, NULL, 0, sysctl_swap_fragmentation, "A",
"Swap Fragmentation Info");
static struct sx sw_alloc_sx;
/*
* "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 pagerlst swap_pager_object_list[NOBJLISTS];
static uma_zone_t swwbuf_zone;
static uma_zone_t swrbuf_zone;
static uma_zone_t swblk_zone;
static uma_zone_t swpctrie_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, struct ucred *);
static void swap_pager_dealloc(vm_object_t object);
static int swap_pager_getpages(vm_object_t, vm_page_t *, int, int *,
int *);
static int swap_pager_getpages_async(vm_object_t, vm_page_t *, int, int *,
int *, pgo_getpages_iodone_t, void *);
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);
static void swap_pager_update_writecount(vm_object_t object,
vm_offset_t start, vm_offset_t end);
static void swap_pager_release_writecount(vm_object_t object,
vm_offset_t start, vm_offset_t end);
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_getpages_async = swap_pager_getpages_async, /* pagein (async) */
.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 */
.pgo_update_writecount = swap_pager_update_writecount,
.pgo_release_writecount = swap_pager_release_writecount,
};
/*
* swap_*() routines are externally accessible. swp_*() routines are
* internal.
*/
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, &nsw_cluster_max, 0,
"Maximum size of a swap block in pages");
static void swp_sizecheck(void);
static void swp_pager_async_iodone(struct buf *bp);
static bool swp_pager_swblk_empty(struct swblk *sb, int start, int limit);
static void swp_pager_free_empty_swblk(vm_object_t, struct swblk *sb);
static int swapongeom(struct vnode *);
static int swaponvp(struct thread *, struct vnode *, u_long);
static int swapoff_one(struct swdevt *sp, struct ucred *cred);
/*
* Swap bitmap functions
*/
static void swp_pager_freeswapspace(daddr_t blk, daddr_t npages);
static daddr_t swp_pager_getswapspace(int *npages);
/*
* Metadata functions
*/
static daddr_t swp_pager_meta_build(vm_object_t, vm_pindex_t, daddr_t);
static void swp_pager_meta_free(vm_object_t, vm_pindex_t, vm_pindex_t);
static void swp_pager_meta_transfer(vm_object_t src, vm_object_t dst,
vm_pindex_t pindex, vm_pindex_t count);
static void swp_pager_meta_free_all(vm_object_t);
static daddr_t swp_pager_meta_lookup(vm_object_t, vm_pindex_t);
static void
swp_pager_init_freerange(daddr_t *start, daddr_t *num)
{
*start = SWAPBLK_NONE;
*num = 0;
}
static void
swp_pager_update_freerange(daddr_t *start, daddr_t *num, daddr_t addr)
{
if (*start + *num == addr) {
(*num)++;
} else {
swp_pager_freeswapspace(*start, *num);
*start = addr;
*num = 1;
}
}
static void *
swblk_trie_alloc(struct pctrie *ptree)
{
return (uma_zalloc(swpctrie_zone, M_NOWAIT | (curproc == pageproc ?
M_USE_RESERVE : 0)));
}
static void
swblk_trie_free(struct pctrie *ptree, void *node)
{
uma_zfree(swpctrie_zone, node);
}
PCTRIE_DEFINE(SWAP, swblk, p, swblk_trie_alloc, swblk_trie_free);
/*
* 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.
*/
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;
}
}
/*
* 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_dev_mtx, "swapdev", NULL, MTX_DEF);
sx_init(&sw_alloc_sx, "swspsx");
sx_init(&swdev_syscall_lock, "swsysc");
}
/*
* 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)
{
unsigned long 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, which has maxphys / PAGE_SIZE entries, 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);
nsw_wcount_async = 4;
nsw_wcount_async_max = nsw_wcount_async;
mtx_init(&swbuf_mtx, "async swbuf mutex", NULL, MTX_DEF);
swwbuf_zone = pbuf_zsecond_create("swwbuf", nswbuf / 4);
swrbuf_zone = pbuf_zsecond_create("swrbuf", nswbuf / 2);
/*
* Initialize our zone, taking the user's requested size or
* estimating the number we need based on the number of pages
* in the system.
*/
n = maxswzone != 0 ? maxswzone / sizeof(struct swblk) :
vm_cnt.v_page_count / 2;
swpctrie_zone = uma_zcreate("swpctrie", pctrie_node_size(), NULL, NULL,
pctrie_zone_init, NULL, UMA_ALIGN_PTR, 0);
if (swpctrie_zone == NULL)
panic("failed to create swap pctrie zone.");
swblk_zone = uma_zcreate("swblk", sizeof(struct swblk), NULL, NULL,
NULL, NULL, _Alignof(struct swblk) - 1, 0);
if (swblk_zone == NULL)
panic("failed to create swap blk zone.");
n2 = n;
do {
if (uma_zone_reserve_kva(swblk_zone, n))
break;
/*
* if the allocation failed, try a zone two thirds the
* size of the previous attempt.
*/
n -= ((n + 2) / 3);
} while (n > 0);
/*
* Often uma_zone_reserve_kva() cannot reserve exactly the
* requested size. Account for the difference when
* calculating swap_maxpages.
*/
n = uma_zone_get_max(swblk_zone);
if (n < n2)
printf("Swap blk zone entries changed from %lu to %lu.\n",
n2, n);
/* absolute maximum we can handle assuming 100% efficiency */
swap_maxpages = n * SWAP_META_PAGES;
swzone = n * sizeof(struct swblk);
if (!uma_zone_reserve_kva(swpctrie_zone, n))
printf("Cannot reserve swap pctrie zone, "
"reduce kern.maxswzone.\n");
}
static vm_object_t
swap_pager_alloc_init(void *handle, struct ucred *cred, vm_ooffset_t size,
vm_ooffset_t offset)
{
vm_object_t object;
if (cred != NULL) {
if (!swap_reserve_by_cred(size, cred))
return (NULL);
crhold(cred);
}
/*
* The un_pager.swp.swp_blks trie is initialized by
* vm_object_allocate() to ensure the correct order of
* visibility to other threads.
*/
object = vm_object_allocate(OBJT_SWAP, OFF_TO_IDX(offset +
PAGE_MASK + size));
object->un_pager.swp.writemappings = 0;
object->handle = handle;
if (cred != NULL) {
object->cred = cred;
object->charge = size;
}
return (object);
}
/*
* 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.
*
* This routine must ensure that no live duplicate is created for
* the named object request, which is protected against by
* holding the sw_alloc_sx lock in case handle != NULL.
*/
static vm_object_t
swap_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
vm_ooffset_t offset, struct ucred *cred)
{
vm_object_t object;
if (handle != NULL) {
/*
* 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) {
object = swap_pager_alloc_init(handle, cred, size,
offset);
if (object != NULL) {
TAILQ_INSERT_TAIL(NOBJLIST(object->handle),
object, pager_object_list);
}
}
sx_xunlock(&sw_alloc_sx);
} else {
object = swap_pager_alloc_init(handle, cred, size, offset);
}
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.
*
* The object must be locked.
*/
static void
swap_pager_dealloc(vm_object_t object)
{
VM_OBJECT_ASSERT_WLOCKED(object);
KASSERT((object->flags & OBJ_DEAD) != 0, ("dealloc of reachable obj"));
/*
* Remove from list right away so lookups will fail if we block for
* pageout completion.
*/
if ((object->flags & OBJ_ANON) == 0 && object->handle != NULL) {
VM_OBJECT_WUNLOCK(object);
sx_xlock(&sw_alloc_sx);
TAILQ_REMOVE(NOBJLIST(object->handle), object,
pager_object_list);
sx_xunlock(&sw_alloc_sx);
VM_OBJECT_WLOCK(object);
}
vm_object_pip_wait(object, "swpdea");
/*
* Free all remaining metadata. We only bother to free it from
* the swap meta data. We do not attempt to free swapblk's still
* associated with vm_page_t's for this object. We do not care
* if paging is still in progress on some objects.
*/
swp_pager_meta_free_all(object);
object->handle = NULL;
object->type = OBJT_DEAD;
}
/************************************************************************
* SWAP PAGER BITMAP ROUTINES *
************************************************************************/
/*
* SWP_PAGER_GETSWAPSPACE() - allocate raw swap space
*
* Allocate swap for up to 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.
*
* This routine may not sleep.
*
* We allocate in round-robin fashion from the configured devices.
*/
static daddr_t
swp_pager_getswapspace(int *io_npages)
{
daddr_t blk;
struct swdevt *sp;
int mpages, npages;
KASSERT(*io_npages >= 1,
("%s: npages not positive", __func__));
blk = SWAPBLK_NONE;
mpages = *io_npages;
npages = imin(BLIST_MAX_ALLOC, mpages);
mtx_lock(&sw_dev_mtx);
sp = swdevhd;
while (!TAILQ_EMPTY(&swtailq)) {
if (sp == NULL)
sp = TAILQ_FIRST(&swtailq);
if ((sp->sw_flags & SW_CLOSING) == 0)
blk = blist_alloc(sp->sw_blist, &npages, mpages);
if (blk != SWAPBLK_NONE)
break;
sp = TAILQ_NEXT(sp, sw_list);
if (swdevhd == sp) {
if (npages == 1)
break;
mpages = npages - 1;
npages >>= 1;
}
}
if (blk != SWAPBLK_NONE) {
*io_npages = npages;
blk += sp->sw_first;
sp->sw_used += npages;
swap_pager_avail -= npages;
swp_sizecheck();
swdevhd = TAILQ_NEXT(sp, sw_list);
} else {
if (swap_pager_full != 2) {
printf("swp_pager_getswapspace(%d): failed\n",
*io_npages);
swap_pager_full = 2;
swap_pager_almost_full = 1;
}
swdevhd = NULL;
}
mtx_unlock(&sw_dev_mtx);
return (blk);
}
static bool
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 (swp_pager_isondev(bp->b_blkno, sp)) {
mtx_unlock(&sw_dev_mtx);
if ((sp->sw_flags & SW_UNMAPPED) != 0 &&
unmapped_buf_allowed) {
bp->b_data = unmapped_buf;
bp->b_offset = 0;
} else {
pmap_qenter((vm_offset_t)bp->b_data,
&bp->b_pages[0], bp->b_bcount / PAGE_SIZE);
}
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.
*
* This routine may not sleep.
*/
static void
swp_pager_freeswapspace(daddr_t blk, daddr_t npages)
{
struct swdevt *sp;
if (npages == 0)
return;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (swp_pager_isondev(blk, sp)) {
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");
}
/*
* SYSCTL_SWAP_FRAGMENTATION() - produce raw swap space stats
*/
static int
sysctl_swap_fragmentation(SYSCTL_HANDLER_ARGS)
{
struct sbuf sbuf;
struct swdevt *sp;
const char *devname;
int error;
error = sysctl_wire_old_buffer(req, 0);
if (error != 0)
return (error);
sbuf_new_for_sysctl(&sbuf, NULL, 128, req);
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (vn_isdisk(sp->sw_vp))
devname = devtoname(sp->sw_vp->v_rdev);
else
devname = "[file]";
sbuf_printf(&sbuf, "\nFree space on device %s:\n", devname);
blist_stats(sp->sw_blist, &sbuf);
}
mtx_unlock(&sw_dev_mtx);
error = sbuf_finish(&sbuf);
sbuf_delete(&sbuf);
return (error);
}
/*
* 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.
*
* The object must be locked.
*/
void
swap_pager_freespace(vm_object_t object, vm_pindex_t start, vm_size_t size)
{
swp_pager_meta_free(object, start, size);
}
/*
* SWAP_PAGER_RESERVE() - reserve swap blocks in object
*
* Assigns swap blocks to the specified range within the object. The
* swap blocks are not zeroed. 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)
{
daddr_t addr, blk, n_free, s_free;
int i, j, n;
swp_pager_init_freerange(&s_free, &n_free);
VM_OBJECT_WLOCK(object);
for (i = 0; i < size; i += n) {
n = size - i;
blk = swp_pager_getswapspace(&n);
if (blk == SWAPBLK_NONE) {
swp_pager_meta_free(object, start, i);
VM_OBJECT_WUNLOCK(object);
return (-1);
}
for (j = 0; j < n; ++j) {
addr = swp_pager_meta_build(object,
start + i + j, blk + j);
if (addr != SWAPBLK_NONE)
swp_pager_update_freerange(&s_free, &n_free,
addr);
}
}
swp_pager_freeswapspace(s_free, n_free);
VM_OBJECT_WUNLOCK(object);
return (0);
}
static bool
swp_pager_xfer_source(vm_object_t srcobject, vm_object_t dstobject,
vm_pindex_t pindex, daddr_t addr)
{
daddr_t dstaddr;
KASSERT(srcobject->type == OBJT_SWAP,
("%s: Srcobject not swappable", __func__));
if (dstobject->type == OBJT_SWAP &&
swp_pager_meta_lookup(dstobject, pindex) != SWAPBLK_NONE) {
/* Caller should destroy the source block. */
return (false);
}
/*
* Destination has no swapblk and is not resident, transfer source.
* swp_pager_meta_build() can sleep.
*/
VM_OBJECT_WUNLOCK(srcobject);
dstaddr = swp_pager_meta_build(dstobject, pindex, addr);
KASSERT(dstaddr == SWAPBLK_NONE,
("Unexpected destination swapblk"));
VM_OBJECT_WLOCK(srcobject);
return (true);
}
/*
* 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 sleep. It may sleep allocating metadata
* indirectly through swp_pager_meta_build().
*
* 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.
* Both object locks may temporarily be released.
*/
void
swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject,
vm_pindex_t offset, int destroysource)
{
VM_OBJECT_ASSERT_WLOCKED(srcobject);
VM_OBJECT_ASSERT_WLOCKED(dstobject);
/*
* If destroysource is set, we remove the source object from the
* swap_pager internal queue now.
*/
if (destroysource && (srcobject->flags & OBJ_ANON) == 0 &&
srcobject->handle != NULL) {
VM_OBJECT_WUNLOCK(srcobject);
VM_OBJECT_WUNLOCK(dstobject);
sx_xlock(&sw_alloc_sx);
TAILQ_REMOVE(NOBJLIST(srcobject->handle), srcobject,
pager_object_list);
sx_xunlock(&sw_alloc_sx);
VM_OBJECT_WLOCK(dstobject);
VM_OBJECT_WLOCK(srcobject);
}
/*
* Transfer source to destination.
*/
swp_pager_meta_transfer(srcobject, dstobject, offset, dstobject->size);
/*
* Free left over swap blocks in source.
*
* We have to revert the type to OBJT_DEFAULT so we do not accidentally
* 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;
}
}
/*
* 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.
*/
static boolean_t
swap_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
int *after)
{
daddr_t blk, blk0;
int i;
VM_OBJECT_ASSERT_LOCKED(object);
KASSERT(object->type == OBJT_SWAP,
("%s: object not swappable", __func__));
/*
* do we have good backing store at the requested index ?
*/
blk0 = swp_pager_meta_lookup(object, pindex);
if (blk0 == SWAPBLK_NONE) {
if (before)
*before = 0;
if (after)
*after = 0;
return (FALSE);
}
/*
* find backwards-looking contiguous good backing store
*/
if (before != NULL) {
for (i = 1; i < SWB_NPAGES; i++) {
if (i > pindex)
break;
blk = swp_pager_meta_lookup(object, pindex - i);
if (blk != blk0 - i)
break;
}
*before = i - 1;
}
/*
* find forward-looking contiguous good backing store
*/
if (after != NULL) {
for (i = 1; i < SWB_NPAGES; i++) {
blk = swp_pager_meta_lookup(object, pindex + i);
if (blk != blk0 + i)
break;
}
*after = i - 1;
}
return (TRUE);
}
/*
* SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page
*
* This removes any associated swap backing store, whether valid or
* not, from the page.
*
* This routine is typically called when a page is made dirty, at
* which point any associated swap can be freed. MADV_FREE also
* calls us in a special-case situation
*
* NOTE!!! If the page is clean and the swap was valid, the caller
* should make the page dirty before calling this routine. This routine
* does NOT change the m->dirty status of the page. Also: MADV_FREE
* depends on it.
*
* This routine may not sleep.
*
* The object containing the page may be locked.
*/
static void
swap_pager_unswapped(vm_page_t m)
{
struct swblk *sb;
vm_object_t obj;
/*
* Handle enqueing deferred frees first. If we do not have the
* object lock we wait for the page daemon to clear the space.
*/
obj = m->object;
if (!VM_OBJECT_WOWNED(obj)) {
VM_PAGE_OBJECT_BUSY_ASSERT(m);
/*
* The caller is responsible for synchronization but we
* will harmlessly handle races. This is typically provided
* by only calling unswapped() when a page transitions from
* clean to dirty.
*/
if ((m->a.flags & (PGA_SWAP_SPACE | PGA_SWAP_FREE)) ==
PGA_SWAP_SPACE) {
vm_page_aflag_set(m, PGA_SWAP_FREE);
counter_u64_add(swap_free_deferred, 1);
}
return;
}
if ((m->a.flags & PGA_SWAP_FREE) != 0)
counter_u64_add(swap_free_completed, 1);
vm_page_aflag_clear(m, PGA_SWAP_FREE | PGA_SWAP_SPACE);
/*
* The meta data only exists if the object is OBJT_SWAP
* and even then might not be allocated yet.
*/
KASSERT(m->object->type == OBJT_SWAP,
("Free object not swappable"));
sb = SWAP_PCTRIE_LOOKUP(&m->object->un_pager.swp.swp_blks,
rounddown(m->pindex, SWAP_META_PAGES));
if (sb == NULL)
return;
if (sb->d[m->pindex % SWAP_META_PAGES] == SWAPBLK_NONE)
return;
swp_pager_freeswapspace(sb->d[m->pindex % SWAP_META_PAGES], 1);
sb->d[m->pindex % SWAP_META_PAGES] = SWAPBLK_NONE;
swp_pager_free_empty_swblk(m->object, sb);
}
/*
* swap_pager_getpages() - bring pages in from swap
*
* Attempt to page in the pages in array "ma" of length "count". The
* caller may optionally specify that additional pages preceding and
* succeeding the specified range be paged in. The number of such pages
* is returned in the "rbehind" and "rahead" parameters, and they will
* be in the inactive queue upon return.
*
* The pages in "ma" must be busied and will remain busied upon return.
*/
static int
swap_pager_getpages_locked(vm_object_t object, vm_page_t *ma, int count,
int *rbehind, int *rahead)
{
struct buf *bp;
vm_page_t bm, mpred, msucc, p;
vm_pindex_t pindex;
daddr_t blk;
int i, maxahead, maxbehind, reqcount;
VM_OBJECT_ASSERT_WLOCKED(object);
reqcount = count;
KASSERT(object->type == OBJT_SWAP,
("%s: object not swappable", __func__));
if (!swap_pager_haspage(object, ma[0]->pindex, &maxbehind, &maxahead)) {
VM_OBJECT_WUNLOCK(object);
return (VM_PAGER_FAIL);
}
KASSERT(reqcount - 1 <= maxahead,
("page count %d extends beyond swap block", reqcount));
/*
* Do not transfer any pages other than those that are xbusied
* when running during a split or collapse operation. This
* prevents clustering from re-creating pages which are being
* moved into another object.
*/
if ((object->flags & (OBJ_SPLIT | OBJ_DEAD)) != 0) {
maxahead = reqcount - 1;
maxbehind = 0;
}
/*
* Clip the readahead and readbehind ranges to exclude resident pages.
*/
if (rahead != NULL) {
*rahead = imin(*rahead, maxahead - (reqcount - 1));
pindex = ma[reqcount - 1]->pindex;
msucc = TAILQ_NEXT(ma[reqcount - 1], listq);
if (msucc != NULL && msucc->pindex - pindex - 1 < *rahead)
*rahead = msucc->pindex - pindex - 1;
}
if (rbehind != NULL) {
*rbehind = imin(*rbehind, maxbehind);
pindex = ma[0]->pindex;
mpred = TAILQ_PREV(ma[0], pglist, listq);
if (mpred != NULL && pindex - mpred->pindex - 1 < *rbehind)
*rbehind = pindex - mpred->pindex - 1;
}
bm = ma[0];
for (i = 0; i < count; i++)
ma[i]->oflags |= VPO_SWAPINPROG;
/*
* Allocate readahead and readbehind pages.
*/
if (rbehind != NULL) {
for (i = 1; i <= *rbehind; i++) {
p = vm_page_alloc(object, ma[0]->pindex - i,
VM_ALLOC_NORMAL);
if (p == NULL)
break;
p->oflags |= VPO_SWAPINPROG;
bm = p;
}
*rbehind = i - 1;
}
if (rahead != NULL) {
for (i = 0; i < *rahead; i++) {
p = vm_page_alloc(object,
ma[reqcount - 1]->pindex + i + 1, VM_ALLOC_NORMAL);
if (p == NULL)
break;
p->oflags |= VPO_SWAPINPROG;
}
*rahead = i;
}
if (rbehind != NULL)
count += *rbehind;
if (rahead != NULL)
count += *rahead;
vm_object_pip_add(object, count);
pindex = bm->pindex;
blk = swp_pager_meta_lookup(object, pindex);
KASSERT(blk != SWAPBLK_NONE,
("no swap blocking containing %p(%jx)", object, (uintmax_t)pindex));
VM_OBJECT_WUNLOCK(object);
bp = uma_zalloc(swrbuf_zone, M_WAITOK);
MPASS((bp->b_flags & B_MAXPHYS) != 0);
/* Pages cannot leave the object while busy. */
for (i = 0, p = bm; i < count; i++, p = TAILQ_NEXT(p, listq)) {
MPASS(p->pindex == bm->pindex + i);
bp->b_pages[i] = p;
}
bp->b_flags |= B_PAGING;
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;
bp->b_bcount = PAGE_SIZE * count;
bp->b_bufsize = PAGE_SIZE * count;
bp->b_npages = count;
bp->b_pgbefore = rbehind != NULL ? *rbehind : 0;
bp->b_pgafter = rahead != NULL ? *rahead : 0;
VM_CNT_INC(v_swapin);
VM_CNT_ADD(v_swappgsin, count);
/*
* 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 ma[] 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 pages we want to complete. VPO_SWAPINPROG is always
* cleared on completion. If an I/O error occurs, SWAPBLK_NONE
* is set in the metadata for each page in the request.
*/
VM_OBJECT_WLOCK(object);
/* This could be implemented more efficiently with aflags */
while ((ma[0]->oflags & VPO_SWAPINPROG) != 0) {
ma[0]->oflags |= VPO_SWAPSLEEP;
VM_CNT_INC(v_intrans);
if (VM_OBJECT_SLEEP(object, &object->handle, 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_OBJECT_WUNLOCK(object);
/*
* If we had an unrecoverable read error pages will not be valid.
*/
for (i = 0; i < reqcount; i++)
if (ma[i]->valid != VM_PAGE_BITS_ALL)
return (VM_PAGER_ERROR);
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.
*/
}
static int
swap_pager_getpages(vm_object_t object, vm_page_t *ma, int count,
int *rbehind, int *rahead)
{
VM_OBJECT_WLOCK(object);
return (swap_pager_getpages_locked(object, ma, count, rbehind, rahead));
}
/*
* swap_pager_getpages_async():
*
* Right now this is emulation of asynchronous operation on top of
* swap_pager_getpages().
*/
static int
swap_pager_getpages_async(vm_object_t object, vm_page_t *ma, int count,
int *rbehind, int *rahead, pgo_getpages_iodone_t iodone, void *arg)
{
int r, error;
r = swap_pager_getpages(object, ma, count, rbehind, rahead);
switch (r) {
case VM_PAGER_OK:
error = 0;
break;
case VM_PAGER_ERROR:
error = EIO;
break;
case VM_PAGER_FAIL:
error = EINVAL;
break;
default:
panic("unhandled swap_pager_getpages() error %d", r);
}
(iodone)(arg, ma, count, error);
return (r);
}
/*
* 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 whose rtvals[] entry is not set to VM_PAGER_PEND on return.
* We need to unbusy the rest on I/O completion.
*/
static void
swap_pager_putpages(vm_object_t object, vm_page_t *ma, int count,
int flags, int *rtvals)
{
struct buf *bp;
daddr_t addr, blk, n_free, s_free;
vm_page_t mreq;
int i, j, n;
bool async;
KASSERT(count == 0 || ma[0]->object == object,
("%s: object mismatch %p/%p",
__func__, object, ma[0]->object));
/*
* Step 1
*
* Turn object into OBJT_SWAP. Force sync if not a pageout process.
*/
if (object->type != OBJT_SWAP) {
addr = swp_pager_meta_build(object, 0, SWAPBLK_NONE);
KASSERT(addr == SWAPBLK_NONE,
("unexpected object swap block"));
}
VM_OBJECT_WUNLOCK(object);
async = curproc == pageproc && (flags & VM_PAGER_PUT_SYNC) == 0;
swp_pager_init_freerange(&s_free, &n_free);
/*
* Step 2
*
* Assign swap blocks and issue I/O. We reallocate swap on the fly.
* The page is left dirty until the pageout operation completes
* successfully.
*/
for (i = 0; i < count; i += n) {
/* Maximum I/O size is limited by maximum swap block size. */
n = min(count - i, nsw_cluster_max);
if (async) {
mtx_lock(&swbuf_mtx);
while (nsw_wcount_async == 0)
msleep(&nsw_wcount_async, &swbuf_mtx, PVM,
"swbufa", 0);
nsw_wcount_async--;
mtx_unlock(&swbuf_mtx);
}
/* Get a block of swap of size up to size n. */
VM_OBJECT_WLOCK(object);
blk = swp_pager_getswapspace(&n);
if (blk == SWAPBLK_NONE) {
VM_OBJECT_WUNLOCK(object);
mtx_lock(&swbuf_mtx);
if (++nsw_wcount_async == 1)
wakeup(&nsw_wcount_async);
mtx_unlock(&swbuf_mtx);
for (j = 0; j < n; ++j)
rtvals[i + j] = VM_PAGER_FAIL;
continue;
}
for (j = 0; j < n; ++j) {
mreq = ma[i + j];
vm_page_aflag_clear(mreq, PGA_SWAP_FREE);
addr = swp_pager_meta_build(mreq->object, mreq->pindex,
blk + j);
if (addr != SWAPBLK_NONE)
swp_pager_update_freerange(&s_free, &n_free,
addr);
MPASS(mreq->dirty == VM_PAGE_BITS_ALL);
mreq->oflags |= VPO_SWAPINPROG;
}
VM_OBJECT_WUNLOCK(object);
bp = uma_zalloc(swwbuf_zone, M_WAITOK);
MPASS((bp->b_flags & B_MAXPHYS) != 0);
if (async)
bp->b_flags |= B_ASYNC;
bp->b_flags |= B_PAGING;
bp->b_iocmd = BIO_WRITE;
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;
for (j = 0; j < n; j++)
bp->b_pages[j] = ma[i + j];
bp->b_npages = n;
/*
* Must set dirty range for NFS to work.
*/
bp->b_dirtyoff = 0;
bp->b_dirtyend = bp->b_bcount;
VM_CNT_INC(v_swapout);
VM_CNT_ADD(v_swappgsout, bp->b_npages);
/*
* We unconditionally set rtvals[] to VM_PAGER_PEND so that we
* can call the async completion routine at the end of a
* synchronous I/O operation. Otherwise, our caller would
* perform duplicate unbusy and wakeup operations on the page
* and object, respectively.
*/
for (j = 0; j < n; j++)
rtvals[i + j] = VM_PAGER_PEND;
/*
* asynchronous
*
* NOTE: b_blkno is destroyed by the call to swapdev_strategy.
*/
if (async) {
bp->b_iodone = swp_pager_async_iodone;
BUF_KERNPROC(bp);
swp_pager_strategy(bp);
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.
*/
bwait(bp, PVM, "swwrt");
/*
* Now that we are through with the bp, we can call the
* normal async completion, which frees everything up.
*/
swp_pager_async_iodone(bp);
}
swp_pager_freeswapspace(s_free, n_free);
VM_OBJECT_WLOCK(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.
*
* This routine may not sleep.
*/
static void
swp_pager_async_iodone(struct buf *bp)
{
int i;
vm_object_t object = NULL;
/*
* Report error - unless we ran out of memory, in which case
* we've already logged it in swapgeom_strategy().
*/
if (bp->b_ioflags & BIO_ERROR && bp->b_error != ENOMEM) {
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
);
}
/*
* remove the mapping for kernel virtual
*/
if (buf_mapped(bp))
pmap_qremove((vm_offset_t)bp->b_data, bp->b_npages);
else
bp->b_data = bp->b_kvabase;
if (bp->b_npages) {
object = bp->b_pages[0]->object;
VM_OBJECT_WLOCK(object);
}
/*
* 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];
m->oflags &= ~VPO_SWAPINPROG;
if (m->oflags & VPO_SWAPSLEEP) {
m->oflags &= ~VPO_SWAPSLEEP;
wakeup(&object->handle);
}
/* We always have space after I/O, successful or not. */
vm_page_aflag_set(m, PGA_SWAP_SPACE);
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) {
/*
* NOTE: for reads, m->dirty will probably
* be overridden by the original caller of
* getpages so don't play cute tricks here.
*/
vm_page_invalid(m);
} else {
/*
* If a write error occurs, reactivate page
* so it doesn't clog the inactive list,
* then finish the I/O.
*/
MPASS(m->dirty == VM_PAGE_BITS_ALL);
/* PQ_UNSWAPPABLE? */
vm_page_activate(m);
vm_page_sunbusy(m);
}
} else if (bp->b_iocmd == BIO_READ) {
/*
* 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.
*/
KASSERT(!pmap_page_is_mapped(m),
("swp_pager_async_iodone: page %p is mapped", m));
KASSERT(m->dirty == 0,
("swp_pager_async_iodone: page %p is dirty", m));
vm_page_valid(m);
if (i < bp->b_pgbefore ||
i >= bp->b_npages - bp->b_pgafter)
vm_page_readahead_finish(m);
} else {
/*
* For write success, clear the dirty
* status, then finish the I/O ( which decrements the
* busy count and possibly wakes waiter's up ).
* A page is only written to swap after a period of
* inactivity. Therefore, we do not expect it to be
* reused.
*/
KASSERT(!pmap_page_is_write_mapped(m),
("swp_pager_async_iodone: page %p is not write"
" protected", m));
vm_page_undirty(m);
vm_page_deactivate_noreuse(m);
vm_page_sunbusy(m);
}
}
/*
* 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_WUNLOCK(object);
}
/*
* swapdev_strategy() manually sets b_vp and b_bufobj before calling
* bstrategy(). Set them back to NULL now we're done with it, or we'll
* trigger a KASSERT in relpbuf().
*/
if (bp->b_vp) {
bp->b_vp = NULL;
bp->b_bufobj = NULL;
}
/*
* release the physical I/O buffer
*/
if (bp->b_flags & B_ASYNC) {
mtx_lock(&swbuf_mtx);
if (++nsw_wcount_async == 1)
wakeup(&nsw_wcount_async);
mtx_unlock(&swbuf_mtx);
}
uma_zfree((bp->b_iocmd == BIO_READ) ? swrbuf_zone : swwbuf_zone, bp);
}
int
swap_pager_nswapdev(void)
{
return (nswapdev);
}
static void
swp_pager_force_dirty(vm_page_t m)
{
vm_page_dirty(m);
swap_pager_unswapped(m);
vm_page_launder(m);
}
/*
* swap_pager_swapoff_object:
*
* Page in all of the pages that have been paged out for an object
* to a swap device.
*/
static void
swap_pager_swapoff_object(struct swdevt *sp, vm_object_t object)
{
struct swblk *sb;
vm_page_t m;
vm_pindex_t pi;
daddr_t blk;
int i, nv, rahead, rv;
KASSERT(object->type == OBJT_SWAP,
("%s: Object not swappable", __func__));
for (pi = 0; (sb = SWAP_PCTRIE_LOOKUP_GE(
&object->un_pager.swp.swp_blks, pi)) != NULL; ) {
if ((object->flags & OBJ_DEAD) != 0) {
/*
* Make sure that pending writes finish before
* returning.
*/
vm_object_pip_wait(object, "swpoff");
swp_pager_meta_free_all(object);
break;
}
for (i = 0; i < SWAP_META_PAGES; i++) {
/*
* Count the number of contiguous valid blocks.
*/
for (nv = 0; nv < SWAP_META_PAGES - i; nv++) {
blk = sb->d[i + nv];
if (!swp_pager_isondev(blk, sp) ||
blk == SWAPBLK_NONE)
break;
}
if (nv == 0)
continue;
/*
* Look for a page corresponding to the first
* valid block and ensure that any pending paging
* operations on it are complete. If the page is valid,
* mark it dirty and free the swap block. Try to batch
* this operation since it may cause sp to be freed,
* meaning that we must restart the scan. Avoid busying
* valid pages since we may block forever on kernel
* stack pages.
*/
m = vm_page_lookup(object, sb->p + i);
if (m == NULL) {
m = vm_page_alloc(object, sb->p + i,
VM_ALLOC_NORMAL | VM_ALLOC_WAITFAIL);
if (m == NULL)
break;
} else {
if ((m->oflags & VPO_SWAPINPROG) != 0) {
m->oflags |= VPO_SWAPSLEEP;
VM_OBJECT_SLEEP(object, &object->handle,
PSWP, "swpoff", 0);
break;
}
if (vm_page_all_valid(m)) {
do {
swp_pager_force_dirty(m);
} while (--nv > 0 &&
(m = vm_page_next(m)) != NULL &&
vm_page_all_valid(m) &&
(m->oflags & VPO_SWAPINPROG) == 0);
break;
}
if (!vm_page_busy_acquire(m, VM_ALLOC_WAITFAIL))
break;
}
vm_object_pip_add(object, 1);
rahead = SWAP_META_PAGES;
rv = swap_pager_getpages_locked(object, &m, 1, NULL,
&rahead);
if (rv != VM_PAGER_OK)
panic("%s: read from swap failed: %d",
__func__, rv);
vm_object_pip_wakeupn(object, 1);
VM_OBJECT_WLOCK(object);
vm_page_xunbusy(m);
/*
* The object lock was dropped so we must restart the
* scan of this swap block. Pages paged in during this
* iteration will be marked dirty in a future iteration.
*/
break;
}
if (i == SWAP_META_PAGES)
pi = sb->p + SWAP_META_PAGES;
}
}
/*
* 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)
{
vm_object_t object;
int retries;
sx_assert(&swdev_syscall_lock, SA_XLOCKED);
retries = 0;
full_rescan:
mtx_lock(&vm_object_list_mtx);
TAILQ_FOREACH(object, &vm_object_list, object_list) {
if (object->type != OBJT_SWAP)
continue;
mtx_unlock(&vm_object_list_mtx);
/* Depends on type-stability. */
VM_OBJECT_WLOCK(object);
/*
* Dead objects are eventually terminated on their own.
*/
if ((object->flags & OBJ_DEAD) != 0)
goto next_obj;
/*
* Sync with fences placed after pctrie
* initialization. We must not access pctrie below
* unless we checked that our object is swap and not
* dead.
*/
atomic_thread_fence_acq();
if (object->type != OBJT_SWAP)
goto next_obj;
swap_pager_swapoff_object(sp, object);
next_obj:
VM_OBJECT_WUNLOCK(object);
mtx_lock(&vm_object_list_mtx);
}
mtx_unlock(&vm_object_list_mtx);
if (sp->sw_used) {
/*
* 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);
}
pause("swpoff", hz / 20);
goto full_rescan;
}
EVENTHANDLER_INVOKE(swapoff, sp);
}
/************************************************************************
* SWAP META DATA *
************************************************************************
*
* These routines manipulate the swap metadata stored in the
* OBJT_SWAP object.
*
* 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_SWBLK_EMPTY() - is a range of blocks free?
*/
static bool
swp_pager_swblk_empty(struct swblk *sb, int start, int limit)
{
int i;
MPASS(0 <= start && start <= limit && limit <= SWAP_META_PAGES);
for (i = start; i < limit; i++) {
if (sb->d[i] != SWAPBLK_NONE)
return (false);
}
return (true);
}
/*
* SWP_PAGER_FREE_EMPTY_SWBLK() - frees if a block is free
*
* Nothing is done if the block is still in use.
*/
static void
swp_pager_free_empty_swblk(vm_object_t object, struct swblk *sb)
{
if (swp_pager_swblk_empty(sb, 0, SWAP_META_PAGES)) {
SWAP_PCTRIE_REMOVE(&object->un_pager.swp.swp_blks, sb->p);
uma_zfree(swblk_zone, sb);
}
}
/*
* 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 returned.
*/
static daddr_t
swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk)
{
static volatile int swblk_zone_exhausted, swpctrie_zone_exhausted;
struct swblk *sb, *sb1;
vm_pindex_t modpi, rdpi;
daddr_t prev_swapblk;
int error, i;
VM_OBJECT_ASSERT_WLOCKED(object);
/*
* Convert default object to swap object if necessary
*/
if (object->type != OBJT_SWAP) {
pctrie_init(&object->un_pager.swp.swp_blks);
/*
* Ensure that swap_pager_swapoff()'s iteration over
* object_list does not see a garbage pctrie.
*/
atomic_thread_fence_rel();
object->type = OBJT_SWAP;
object->un_pager.swp.writemappings = 0;
KASSERT((object->flags & OBJ_ANON) != 0 ||
object->handle == NULL,
("default pager %p with handle %p",
object, object->handle));
}
rdpi = rounddown(pindex, SWAP_META_PAGES);
sb = SWAP_PCTRIE_LOOKUP(&object->un_pager.swp.swp_blks, rdpi);
if (sb == NULL) {
if (swapblk == SWAPBLK_NONE)
return (SWAPBLK_NONE);
for (;;) {
sb = uma_zalloc(swblk_zone, M_NOWAIT | (curproc ==
pageproc ? M_USE_RESERVE : 0));
if (sb != NULL) {
sb->p = rdpi;
for (i = 0; i < SWAP_META_PAGES; i++)
sb->d[i] = SWAPBLK_NONE;
if (atomic_cmpset_int(&swblk_zone_exhausted,
1, 0))
printf("swblk zone ok\n");
break;
}
VM_OBJECT_WUNLOCK(object);
if (uma_zone_exhausted(swblk_zone)) {
if (atomic_cmpset_int(&swblk_zone_exhausted,
0, 1))
printf("swap blk zone exhausted, "
"increase kern.maxswzone\n");
vm_pageout_oom(VM_OOM_SWAPZ);
pause("swzonxb", 10);
} else
uma_zwait(swblk_zone);
VM_OBJECT_WLOCK(object);
sb = SWAP_PCTRIE_LOOKUP(&object->un_pager.swp.swp_blks,
rdpi);
if (sb != NULL)
/*
* Somebody swapped out a nearby page,
* allocating swblk at the rdpi index,
* while we dropped the object lock.
*/
goto allocated;
}
for (;;) {
error = SWAP_PCTRIE_INSERT(
&object->un_pager.swp.swp_blks, sb);
if (error == 0) {
if (atomic_cmpset_int(&swpctrie_zone_exhausted,
1, 0))
printf("swpctrie zone ok\n");
break;
}
VM_OBJECT_WUNLOCK(object);
if (uma_zone_exhausted(swpctrie_zone)) {
if (atomic_cmpset_int(&swpctrie_zone_exhausted,
0, 1))
printf("swap pctrie zone exhausted, "
"increase kern.maxswzone\n");
vm_pageout_oom(VM_OOM_SWAPZ);
pause("swzonxp", 10);
} else
uma_zwait(swpctrie_zone);
VM_OBJECT_WLOCK(object);
sb1 = SWAP_PCTRIE_LOOKUP(&object->un_pager.swp.swp_blks,
rdpi);
if (sb1 != NULL) {
uma_zfree(swblk_zone, sb);
sb = sb1;
goto allocated;
}
}
}
allocated:
MPASS(sb->p == rdpi);
modpi = pindex % SWAP_META_PAGES;
/* Return prior contents of metadata. */
prev_swapblk = sb->d[modpi];
/* Enter block into metadata. */
sb->d[modpi] = swapblk;
/*
* Free the swblk if we end up with the empty page run.
*/
if (swapblk == SWAPBLK_NONE)
swp_pager_free_empty_swblk(object, sb);
return (prev_swapblk);
}
/*
* SWP_PAGER_META_TRANSFER() - free a range of blocks in the srcobject's swap
* metadata, or transfer it into dstobject.
*
* This routine will free swap metadata structures as they are cleaned
* out.
*/
static void
swp_pager_meta_transfer(vm_object_t srcobject, vm_object_t dstobject,
vm_pindex_t pindex, vm_pindex_t count)
{
struct swblk *sb;
daddr_t n_free, s_free;
vm_pindex_t offset, last;
int i, limit, start;
VM_OBJECT_ASSERT_WLOCKED(srcobject);
if (srcobject->type != OBJT_SWAP || count == 0)
return;
swp_pager_init_freerange(&s_free, &n_free);
offset = pindex;
last = pindex + count;
for (;;) {
sb = SWAP_PCTRIE_LOOKUP_GE(&srcobject->un_pager.swp.swp_blks,
rounddown(pindex, SWAP_META_PAGES));
if (sb == NULL || sb->p >= last)
break;
start = pindex > sb->p ? pindex - sb->p : 0;
limit = last - sb->p < SWAP_META_PAGES ? last - sb->p :
SWAP_META_PAGES;
for (i = start; i < limit; i++) {
if (sb->d[i] == SWAPBLK_NONE)
continue;
if (dstobject == NULL ||
!swp_pager_xfer_source(srcobject, dstobject,
sb->p + i - offset, sb->d[i])) {
swp_pager_update_freerange(&s_free, &n_free,
sb->d[i]);
}
sb->d[i] = SWAPBLK_NONE;
}
pindex = sb->p + SWAP_META_PAGES;
if (swp_pager_swblk_empty(sb, 0, start) &&
swp_pager_swblk_empty(sb, limit, SWAP_META_PAGES)) {
SWAP_PCTRIE_REMOVE(&srcobject->un_pager.swp.swp_blks,
sb->p);
uma_zfree(swblk_zone, sb);
}
}
swp_pager_freeswapspace(s_free, n_free);
}
/*
* 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.
*/
static void
swp_pager_meta_free(vm_object_t object, vm_pindex_t pindex, vm_pindex_t count)
{
swp_pager_meta_transfer(object, NULL, pindex, count);
}
/*
* SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object
*
* This routine locates and destroys all swap metadata associated with
* an object.
*/
static void
swp_pager_meta_free_all(vm_object_t object)
{
struct swblk *sb;
daddr_t n_free, s_free;
vm_pindex_t pindex;
int i;
VM_OBJECT_ASSERT_WLOCKED(object);
if (object->type != OBJT_SWAP)
return;
swp_pager_init_freerange(&s_free, &n_free);
for (pindex = 0; (sb = SWAP_PCTRIE_LOOKUP_GE(
&object->un_pager.swp.swp_blks, pindex)) != NULL;) {
pindex = sb->p + SWAP_META_PAGES;
for (i = 0; i < SWAP_META_PAGES; i++) {
if (sb->d[i] == SWAPBLK_NONE)
continue;
swp_pager_update_freerange(&s_free, &n_free, sb->d[i]);
}
SWAP_PCTRIE_REMOVE(&object->un_pager.swp.swp_blks, sb->p);
uma_zfree(swblk_zone, sb);
}
swp_pager_freeswapspace(s_free, n_free);
}
/*
* SWP_PAGER_METACTL() - misc control of swap meta data.
*
* This routine is capable of looking up, or removing swapblk
* assignments in the swap meta data. It returns the swapblk being
* looked-up, popped, or SWAPBLK_NONE if the block was invalid.
*
* 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.
*/
static daddr_t
swp_pager_meta_lookup(vm_object_t object, vm_pindex_t pindex)
{
struct swblk *sb;
VM_OBJECT_ASSERT_LOCKED(object);
/*
* The meta data only exists if the object is OBJT_SWAP
* and even then might not be allocated yet.
*/
KASSERT(object->type == OBJT_SWAP,
("Lookup object not swappable"));
sb = SWAP_PCTRIE_LOOKUP(&object->un_pager.swp.swp_blks,
rounddown(pindex, SWAP_META_PAGES));
if (sb == NULL)
return (SWAPBLK_NONE);
return (sb->d[pindex % SWAP_META_PAGES]);
}
/*
* Returns the least page index which is greater than or equal to the
* parameter pindex and for which there is a swap block allocated.
* Returns object's size if the object's type is not swap or if there
* are no allocated swap blocks for the object after the requested
* pindex.
*/
vm_pindex_t
swap_pager_find_least(vm_object_t object, vm_pindex_t pindex)
{
struct swblk *sb;
int i;
VM_OBJECT_ASSERT_LOCKED(object);
if (object->type != OBJT_SWAP)
return (object->size);
sb = SWAP_PCTRIE_LOOKUP_GE(&object->un_pager.swp.swp_blks,
rounddown(pindex, SWAP_META_PAGES));
if (sb == NULL)
return (object->size);
if (sb->p < pindex) {
for (i = pindex % SWAP_META_PAGES; i < SWAP_META_PAGES; i++) {
if (sb->d[i] != SWAPBLK_NONE)
return (sb->p + i);
}
sb = SWAP_PCTRIE_LOOKUP_GE(&object->un_pager.swp.swp_blks,
roundup(pindex, SWAP_META_PAGES));
if (sb == NULL)
return (object->size);
}
for (i = 0; i < SWAP_META_PAGES; i++) {
if (sb->d[i] != SWAPBLK_NONE)
return (sb->p + i);
}
/*
* We get here if a swblk is present in the trie but it
* doesn't map any blocks.
*/
MPASS(0);
return (object->size);
}
/*
* 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
sys_swapon(struct thread *td, struct swapon_args *uap)
{
struct vattr attr;
struct vnode *vp;
struct nameidata nd;
int error;
error = priv_check(td, PRIV_SWAPON);
if (error)
return (error);
sx_xlock(&swdev_syscall_lock);
/*
* Swap metadata may not fit in the KVM if we have physical
* memory of >1GB.
*/
if (swblk_zone == NULL) {
error = ENOMEM;
goto done;
}
NDINIT(&nd, LOOKUP, ISOPEN | FOLLOW | AUDITVNODE1, UIO_USERSPACE,
uap->name, td);
error = namei(&nd);
if (error)
goto done;
NDFREE(&nd, NDF_ONLY_PNBUF);
vp = nd.ni_vp;
if (vn_isdisk_error(vp, &error)) {
error = swapongeom(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)) == 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:
sx_xunlock(&swdev_syscall_lock);
return (error);
}
/*
* Check that the total amount of swap currently configured does not
* exceed half the theoretical maximum. If it does, print a warning
* message.
*/
static void
swapon_check_swzone(void)
{
/* recommend using no more than half that amount */
if (swap_total > swap_maxpages / 2) {
printf("warning: total configured swap (%lu pages) "
"exceeds maximum recommended amount (%lu pages).\n",
swap_total, swap_maxpages / 2);
printf("warning: increase kern.maxswzone "
"or reduce amount of swap.\n");
}
}
static void
swaponsomething(struct vnode *vp, void *id, u_long nblks,
sw_strategy_t *strategy, sw_close_t *close, dev_t dev, int flags)
{
struct swdevt *sp, *tsp;
daddr_t dvbase;
/*
* 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_blist = blist_create(nblks, M_WAITOK);
sp->sw_vp = vp;
sp->sw_id = id;
sp->sw_dev = dev;
sp->sw_nblks = nblks;
sp->sw_used = 0;
sp->sw_strategy = strategy;
sp->sw_close = close;
sp->sw_flags = flags;
/*
* Do not free the first blocks in order to avoid overwriting
* any bsd label at the front of the partition
*/
blist_free(sp->sw_blist, howmany(BBSIZE, PAGE_SIZE),
nblks - howmany(BBSIZE, PAGE_SIZE));
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 - howmany(BBSIZE, PAGE_SIZE);
swap_total += nblks;
swapon_check_swzone();
swp_sizecheck();
mtx_unlock(&sw_dev_mtx);
EVENTHANDLER_INVOKE(swapon, sp);
}
/*
* 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
sys_swapoff(struct thread *td, struct swapoff_args *uap)
{
struct vnode *vp;
struct nameidata nd;
struct swdevt *sp;
int error;
error = priv_check(td, PRIV_SWAPOFF);
if (error)
return (error);
sx_xlock(&swdev_syscall_lock);
NDINIT(&nd, LOOKUP, FOLLOW | AUDITVNODE1, 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)
break;
}
mtx_unlock(&sw_dev_mtx);
if (sp == NULL) {
error = EINVAL;
goto done;
}
error = swapoff_one(sp, td->td_ucred);
done:
sx_xunlock(&swdev_syscall_lock);
return (error);
}
static int
swapoff_one(struct swdevt *sp, struct ucred *cred)
{
u_long nblks;
#ifdef MAC
int error;
#endif
sx_assert(&swdev_syscall_lock, SA_XLOCKED);
#ifdef MAC
(void) vn_lock(sp->sw_vp, LK_EXCLUSIVE | LK_RETRY);
error = mac_system_check_swapoff(cred, sp->sw_vp);
(void) VOP_UNLOCK(sp->sw_vp);
if (error != 0)
return (error);
#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 (vm_free_count() + swap_pager_avail < nblks + nswap_lowat)
return (ENOMEM);
/*
* Prevent further allocations on this device.
*/
mtx_lock(&sw_dev_mtx);
sp->sw_flags |= SW_CLOSING;
swap_pager_avail -= blist_fill(sp->sw_blist, 0, nblks);
swap_total -= nblks;
mtx_unlock(&sw_dev_mtx);
/*
* Page in the contents of the device and close it.
*/
swap_pager_swapoff(sp);
sp->sw_close(curthread, sp);
mtx_lock(&sw_dev_mtx);
sp->sw_id = NULL;
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);
return (0);
}
void
swapoff_all(void)
{
struct swdevt *sp, *spt;
const char *devname;
int error;
sx_xlock(&swdev_syscall_lock);
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH_SAFE(sp, &swtailq, sw_list, spt) {
mtx_unlock(&sw_dev_mtx);
if (vn_isdisk(sp->sw_vp))
devname = devtoname(sp->sw_vp->v_rdev);
else
devname = "[file]";
error = swapoff_one(sp, thread0.td_ucred);
if (error != 0) {
printf("Cannot remove swap device %s (error=%d), "
"skipping.\n", devname, error);
} else if (bootverbose) {
printf("Swap device %s removed.\n", devname);
}
mtx_lock(&sw_dev_mtx);
}
mtx_unlock(&sw_dev_mtx);
sx_xunlock(&swdev_syscall_lock);
}
void
swap_pager_status(int *total, int *used)
{
*total = swap_total;
*used = swap_total - swap_pager_avail -
nswapdev * howmany(BBSIZE, PAGE_SIZE);
}
int
swap_dev_info(int name, struct xswdev *xs, char *devname, size_t len)
{
struct swdevt *sp;
const char *tmp_devname;
int error, n;
n = 0;
error = ENOENT;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (n != name) {
n++;
continue;
}
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;
if (devname != NULL) {
if (vn_isdisk(sp->sw_vp))
tmp_devname = devtoname(sp->sw_vp->v_rdev);
else
tmp_devname = "[file]";
strncpy(devname, tmp_devname, len);
}
error = 0;
break;
}
mtx_unlock(&sw_dev_mtx);
return (error);
}
#if defined(COMPAT_FREEBSD11)
#define XSWDEV_VERSION_11 1
struct xswdev11 {
u_int xsw_version;
uint32_t xsw_dev;
int xsw_flags;
int xsw_nblks;
int xsw_used;
};
#endif
#if defined(__amd64__) && defined(COMPAT_FREEBSD32)
struct xswdev32 {
u_int xsw_version;
u_int xsw_dev1, xsw_dev2;
int xsw_flags;
int xsw_nblks;
int xsw_used;
};
#endif
static int
sysctl_vm_swap_info(SYSCTL_HANDLER_ARGS)
{
struct xswdev xs;
#if defined(__amd64__) && defined(COMPAT_FREEBSD32)
struct xswdev32 xs32;
#endif
#if defined(COMPAT_FREEBSD11)
struct xswdev11 xs11;
#endif
int error;
if (arg2 != 1) /* name length */
return (EINVAL);
error = swap_dev_info(*(int *)arg1, &xs, NULL, 0);
if (error != 0)
return (error);
#if defined(__amd64__) && defined(COMPAT_FREEBSD32)
if (req->oldlen == sizeof(xs32)) {
xs32.xsw_version = XSWDEV_VERSION;
xs32.xsw_dev1 = xs.xsw_dev;
xs32.xsw_dev2 = xs.xsw_dev >> 32;
xs32.xsw_flags = xs.xsw_flags;
xs32.xsw_nblks = xs.xsw_nblks;
xs32.xsw_used = xs.xsw_used;
error = SYSCTL_OUT(req, &xs32, sizeof(xs32));
return (error);
}
#endif
#if defined(COMPAT_FREEBSD11)
if (req->oldlen == sizeof(xs11)) {
xs11.xsw_version = XSWDEV_VERSION_11;
xs11.xsw_dev = xs.xsw_dev; /* truncation */
xs11.xsw_flags = xs.xsw_flags;
xs11.xsw_nblks = xs.xsw_nblks;
xs11.xsw_used = xs.xsw_used;
error = SYSCTL_OUT(req, &xs11, sizeof(xs11));
return (error);
}
#endif
error = SYSCTL_OUT(req, &xs, sizeof(xs));
return (error);
}
SYSCTL_INT(_vm, OID_AUTO, nswapdev, CTLFLAG_RD, &nswapdev, 0,
"Number of swap devices");
SYSCTL_NODE(_vm, OID_AUTO, swap_info, CTLFLAG_RD | CTLFLAG_MPSAFE,
sysctl_vm_swap_info,
"Swap statistics by device");
/*
* Count the approximate swap usage in pages for a vmspace. The
* shadowed or not yet copied on write swap blocks are not accounted.
* The map must be locked.
*/
long
vmspace_swap_count(struct vmspace *vmspace)
{
vm_map_t map;
vm_map_entry_t cur;
vm_object_t object;
struct swblk *sb;
vm_pindex_t e, pi;
long count;
int i;
map = &vmspace->vm_map;
count = 0;
VM_MAP_ENTRY_FOREACH(cur, map) {
if ((cur->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
continue;
object = cur->object.vm_object;
if (object == NULL || object->type != OBJT_SWAP)
continue;
VM_OBJECT_RLOCK(object);
if (object->type != OBJT_SWAP)
goto unlock;
pi = OFF_TO_IDX(cur->offset);
e = pi + OFF_TO_IDX(cur->end - cur->start);
for (;; pi = sb->p + SWAP_META_PAGES) {
sb = SWAP_PCTRIE_LOOKUP_GE(
&object->un_pager.swp.swp_blks, pi);
if (sb == NULL || sb->p >= e)
break;
for (i = 0; i < SWAP_META_PAGES; i++) {
if (sb->p + i < e &&
sb->d[i] != SWAPBLK_NONE)
count++;
}
}
unlock:
VM_OBJECT_RUNLOCK(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_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);
}
/*
* Add a reference to the g_consumer for an inflight transaction.
*/
static void
swapgeom_acquire(struct g_consumer *cp)
{
mtx_assert(&sw_dev_mtx, MA_OWNED);
cp->index++;
}
/*
* Remove a reference from the g_consumer. Post a close event if all
* references go away, since the function might be called from the
* biodone context.
*/
static void
swapgeom_release(struct g_consumer *cp, struct swdevt *sp)
{
mtx_assert(&sw_dev_mtx, MA_OWNED);
cp->index--;
if (cp->index == 0) {
if (g_post_event(swapgeom_close_ev, cp, M_NOWAIT, NULL) == 0)
sp->sw_id = NULL;
}
}
static void
swapgeom_done(struct bio *bp2)
{
struct swdevt *sp;
struct buf *bp;
struct g_consumer *cp;
bp = bp2->bio_caller2;
cp = bp2->bio_from;
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;
bp->b_caller1 = NULL;
bufdone(bp);
sp = bp2->bio_caller1;
mtx_lock(&sw_dev_mtx);
swapgeom_release(cp, sp);
mtx_unlock(&sw_dev_mtx);
g_destroy_bio(bp2);
}
static void
swapgeom_strategy(struct buf *bp, struct swdevt *sp)
{
struct bio *bio;
struct g_consumer *cp;
mtx_lock(&sw_dev_mtx);
cp = sp->sw_id;
if (cp == NULL) {
mtx_unlock(&sw_dev_mtx);
bp->b_error = ENXIO;
bp->b_ioflags |= BIO_ERROR;
bufdone(bp);
return;
}
swapgeom_acquire(cp);
mtx_unlock(&sw_dev_mtx);
if (bp->b_iocmd == BIO_WRITE)
bio = g_new_bio();
else
bio = g_alloc_bio();
if (bio == NULL) {
mtx_lock(&sw_dev_mtx);
swapgeom_release(cp, sp);
mtx_unlock(&sw_dev_mtx);
bp->b_error = ENOMEM;
bp->b_ioflags |= BIO_ERROR;
printf("swap_pager: cannot allocate bio\n");
bufdone(bp);
return;
}
bp->b_caller1 = bio;
bio->bio_caller1 = sp;
bio->bio_caller2 = bp;
bio->bio_cmd = bp->b_iocmd;
bio->bio_offset = (bp->b_blkno - sp->sw_first) * PAGE_SIZE;
bio->bio_length = bp->b_bcount;
bio->bio_done = swapgeom_done;
if (!buf_mapped(bp)) {
bio->bio_ma = bp->b_pages;
bio->bio_data = unmapped_buf;
bio->bio_ma_offset = (vm_offset_t)bp->b_offset & PAGE_MASK;
bio->bio_ma_n = bp->b_npages;
bio->bio_flags |= BIO_UNMAPPED;
} else {
bio->bio_data = bp->b_data;
bio->bio_ma = NULL;
}
g_io_request(bio, cp);
return;
}
static void
swapgeom_orphan(struct g_consumer *cp)
{
struct swdevt *sp;
int destroy;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (sp->sw_id == cp) {
sp->sw_flags |= SW_CLOSING;
break;
}
}
/*
* Drop reference we were created with. Do directly since we're in a
* special context where we don't have to queue the call to
* swapgeom_close_ev().
*/
cp->index--;
destroy = ((sp != NULL) && (cp->index == 0));
if (destroy)
sp->sw_id = NULL;
mtx_unlock(&sw_dev_mtx);
if (destroy)
swapgeom_close_ev(cp, 0);
}
static void
swapgeom_close(struct thread *td, struct swdevt *sw)
{
struct g_consumer *cp;
mtx_lock(&sw_dev_mtx);
cp = sw->sw_id;
sw->sw_id = NULL;
mtx_unlock(&sw_dev_mtx);
/*
* swapgeom_close() may be called from the biodone context,
* where we cannot perform topology changes. Delegate the
* work to the events thread.
*/
if (cp != NULL)
g_waitfor_event(swapgeom_close_ev, cp, M_WAITOK, NULL);
}
static int
swapongeom_locked(struct cdev *dev, struct vnode *vp)
{
struct g_provider *pp;
struct g_consumer *cp;
static struct g_geom *gp;
struct swdevt *sp;
u_long nblks;
int error;
pp = g_dev_getprovider(dev);
if (pp == NULL)
return (ENODEV);
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);
return (EBUSY);
}
}
mtx_unlock(&sw_dev_mtx);
if (gp == NULL)
gp = g_new_geomf(&g_swap_class, "swap");
cp = g_new_consumer(gp);
cp->index = 1; /* Number of active I/Os, plus one for being active. */
cp->flags |= G_CF_DIRECT_SEND | G_CF_DIRECT_RECEIVE;
g_attach(cp, pp);
/*
* XXX: Every time 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 != 0) {
g_detach(cp);
g_destroy_consumer(cp);
return (error);
}
nblks = pp->mediasize / DEV_BSIZE;
swaponsomething(vp, cp, nblks, swapgeom_strategy,
swapgeom_close, dev2udev(dev),
(pp->flags & G_PF_ACCEPT_UNMAPPED) != 0 ? SW_UNMAPPED : 0);
return (0);
}
static int
swapongeom(struct vnode *vp)
{
int error;
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
if (vp->v_type != VCHR || VN_IS_DOOMED(vp)) {
error = ENOENT;
} else {
g_topology_lock();
error = swapongeom_locked(vp->v_rdev, vp);
g_topology_unlock();
}
VOP_UNLOCK(vp);
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)
{
struct vnode *vp2;
bp->b_blkno = ctodb(bp->b_blkno - sp->sw_first);
vp2 = sp->sw_id;
vhold(vp2);
if (bp->b_iocmd == BIO_WRITE) {
if (bp->b_bufobj)
bufobj_wdrop(bp->b_bufobj);
bufobj_wref(&vp2->v_bufobj);
}
if (bp->b_bufobj != &vp2->v_bufobj)
bp->b_bufobj = &vp2->v_bufobj;
bp->b_vp = vp2;
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);
#ifdef MAC
error = mac_system_check_swapon(td->td_ucred, vp);
if (error == 0)
#endif
error = VOP_OPEN(vp, FREAD | FWRITE, td->td_ucred, td, NULL);
(void) VOP_UNLOCK(vp);
if (error)
return (error);
swaponsomething(vp, vp, nblks, swapdev_strategy, swapdev_close,
NODEV, 0);
return (0);
}
static int
sysctl_swap_async_max(SYSCTL_HANDLER_ARGS)
{
int error, new, n;
new = nsw_wcount_async_max;
error = sysctl_handle_int(oidp, &new, 0, req);
if (error != 0 || req->newptr == NULL)
return (error);
if (new > nswbuf / 2 || new < 1)
return (EINVAL);
mtx_lock(&swbuf_mtx);
while (nsw_wcount_async_max != new) {
/*
* Adjust difference. If the current async count is too low,
* we will need to sqeeze our update slowly in. Sleep with a
* higher priority than getpbuf() to finish faster.
*/
n = new - nsw_wcount_async_max;
if (nsw_wcount_async + n >= 0) {
nsw_wcount_async += n;
nsw_wcount_async_max += n;
wakeup(&nsw_wcount_async);
} else {
nsw_wcount_async_max -= nsw_wcount_async;
nsw_wcount_async = 0;
msleep(&nsw_wcount_async, &swbuf_mtx, PSWP,
"swpsysctl", 0);
}
}
mtx_unlock(&swbuf_mtx);
return (0);
}
static void
swap_pager_update_writecount(vm_object_t object, vm_offset_t start,
vm_offset_t end)
{
VM_OBJECT_WLOCK(object);
KASSERT((object->flags & OBJ_ANON) == 0,
("Splittable object with writecount"));
object->un_pager.swp.writemappings += (vm_ooffset_t)end - start;
VM_OBJECT_WUNLOCK(object);
}
static void
swap_pager_release_writecount(vm_object_t object, vm_offset_t start,
vm_offset_t end)
{
VM_OBJECT_WLOCK(object);
KASSERT((object->flags & OBJ_ANON) == 0,
("Splittable object with writecount"));
object->un_pager.swp.writemappings -= (vm_ooffset_t)end - start;
VM_OBJECT_WUNLOCK(object);
}
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