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freebsd-skq/sys/vm/swap_pager.c
Doug Moore 7b9bcad939 A style-related change, r349791, made unclear the meaning of a 
comment. Rewrite that comment to improve its clarity.

Reported by: cem
Reviewed by: alc, cem
Approved by: kib, markj (mentors, implicit)
Differential Revision: https://reviews.freebsd.org/D20871
2019-07-07 06:57:04 +00:00

3005 lines
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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/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 u_long swap_reserved;
static u_long swap_total;
static int sysctl_page_shift(SYSCTL_HANDLER_ARGS);
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");
/* 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));
}
int
swap_reserve(vm_ooffset_t incr)
{
return (swap_reserve_by_cred(incr, curthread->td_ucred));
}
int
swap_reserve_by_cred(vm_ooffset_t incr, struct ucred *cred)
{
u_long r, s, prev, pincr;
int res, error;
static int curfail;
static struct timeval lastfail;
struct uidinfo *uip;
uip = cred->cr_ruidinfo;
KASSERT((incr & PAGE_MASK) == 0, ("%s: incr: %ju & PAGE_MASK", __func__,
(uintmax_t)incr));
#ifdef RACCT
if (racct_enable) {
PROC_LOCK(curproc);
error = racct_add(curproc, RACCT_SWAP, incr);
PROC_UNLOCK(curproc);
if (error != 0)
return (0);
}
#endif
pincr = atop(incr);
res = 0;
prev = atomic_fetchadd_long(&swap_reserved, pincr);
r = prev + pincr;
if (overcommit & SWAP_RESERVE_ALLOW_NONWIRED) {
s = vm_cnt.v_page_count - vm_cnt.v_free_reserved -
vm_wire_count();
} else
s = 0;
s += swap_total;
if ((overcommit & SWAP_RESERVE_FORCE_ON) == 0 || r <= s ||
(error = priv_check(curthread, PRIV_VM_SWAP_NOQUOTA)) == 0) {
res = 1;
} else {
prev = atomic_fetchadd_long(&swap_reserved, -pincr);
if (prev < pincr)
panic("swap_reserved < incr on overcommit fail");
}
if (res) {
prev = atomic_fetchadd_long(&uip->ui_vmsize, pincr);
if ((overcommit & SWAP_RESERVE_RLIMIT_ON) != 0 &&
prev + pincr > lim_cur(curthread, RLIMIT_SWAP) &&
priv_check(curthread, PRIV_VM_SWAP_NORLIMIT)) {
res = 0;
prev = atomic_fetchadd_long(&uip->ui_vmsize, -pincr);
if (prev < pincr)
panic("uip->ui_vmsize < incr on overcommit fail");
}
}
if (!res && ppsratecheck(&lastfail, &curfail, 1)) {
printf("uid %d, pid %d: swap reservation for %jd bytes failed\n",
uip->ui_uid, curproc->p_pid, incr);
}
#ifdef RACCT
if (racct_enable && !res) {
PROC_LOCK(curproc);
racct_sub(curproc, RACCT_SWAP, incr);
PROC_UNLOCK(curproc);
}
#endif
return (res);
}
void
swap_reserve_force(vm_ooffset_t incr)
{
struct uidinfo *uip;
u_long pincr;
KASSERT((incr & PAGE_MASK) == 0, ("%s: incr: %ju & PAGE_MASK", __func__,
(uintmax_t)incr));
PROC_LOCK(curproc);
#ifdef RACCT
if (racct_enable)
racct_add_force(curproc, RACCT_SWAP, incr);
#endif
pincr = atop(incr);
atomic_add_long(&swap_reserved, pincr);
uip = curproc->p_ucred->cr_ruidinfo;
atomic_add_long(&uip->ui_vmsize, pincr);
PROC_UNLOCK(curproc);
}
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 prev, pdecr;
struct uidinfo *uip;
uip = cred->cr_ruidinfo;
KASSERT((decr & PAGE_MASK) == 0, ("%s: decr: %ju & PAGE_MASK", __func__,
(uintmax_t)decr));
pdecr = atop(decr);
prev = atomic_fetchadd_long(&swap_reserved, -pdecr);
if (prev < pdecr)
panic("swap_reserved < decr");
prev = atomic_fetchadd_long(&uip->ui_vmsize, -pdecr);
if (prev < pdecr)
printf("negative vmsize for uid = %d\n", uip->ui_uid);
#ifdef RACCT
if (racct_enable)
racct_sub_cred(cred, RACCT_SWAP, decr);
#endif
}
#define SWM_POP 0x01 /* pop out */
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);
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 */
};
/*
* 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 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, int limit);
/*
* 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_free_all(vm_object_t);
static daddr_t swp_pager_meta_ctl(vm_object_t, vm_pindex_t, int);
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, UMA_ZONE_VM);
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, UMA_ZONE_VM);
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);
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->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->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, and at
* least a minimum 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, int limit)
{
daddr_t blk;
struct swdevt *sp;
int mpages, npages;
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 <= limit)
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, NULL))
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, 1);
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);
}
/*
* 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() or if paging is still in
* progress on the source.
*
* 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_pindex_t i;
daddr_t dstaddr, n_free, s_free, srcaddr;
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->handle != NULL) {
vm_object_pip_add(srcobject, 1);
VM_OBJECT_WUNLOCK(srcobject);
vm_object_pip_add(dstobject, 1);
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_pip_wakeup(dstobject);
VM_OBJECT_WLOCK(srcobject);
vm_object_pip_wakeup(srcobject);
}
/*
* Transfer source to destination.
*/
swp_pager_init_freerange(&s_free, &n_free);
for (i = 0; i < dstobject->size; ++i) {
srcaddr = swp_pager_meta_ctl(srcobject, i + offset, SWM_POP);
if (srcaddr == SWAPBLK_NONE)
continue;
dstaddr = swp_pager_meta_ctl(dstobject, i, 0);
if (dstaddr != SWAPBLK_NONE) {
/*
* Destination has valid swapblk or it is represented
* by a resident page. We destroy the source block.
*/
swp_pager_update_freerange(&s_free, &n_free, srcaddr);
continue;
}
/*
* Destination has no swapblk and is not resident,
* copy source.
*
* swp_pager_meta_build() can sleep.
*/
vm_object_pip_add(srcobject, 1);
VM_OBJECT_WUNLOCK(srcobject);
vm_object_pip_add(dstobject, 1);
dstaddr = swp_pager_meta_build(dstobject, i, srcaddr);
KASSERT(dstaddr == SWAPBLK_NONE,
("Unexpected destination swapblk"));
vm_object_pip_wakeup(dstobject);
VM_OBJECT_WLOCK(srcobject);
vm_object_pip_wakeup(srcobject);
}
swp_pager_freeswapspace(s_free, n_free);
/*
* 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);
/*
* do we have good backing store at the requested index ?
*/
blk0 = swp_pager_meta_ctl(object, pindex, 0);
if (blk0 == SWAPBLK_NONE) {
if (before)
*before = 0;
if (after)
*after = 0;
return (FALSE);
}
/*
* find backwards-looking contiguous good backing store
*/
if (before != NULL) {
for (i = 1; i < SWB_NPAGES; i++) {
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) {
for (i = 1; i < SWB_NPAGES; i++) {
blk = swp_pager_meta_ctl(object, pindex + i, 0);
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 must be locked.
*/
static void
swap_pager_unswapped(vm_page_t m)
{
daddr_t srcaddr;
srcaddr = swp_pager_meta_ctl(m->object, m->pindex, SWM_POP);
if (srcaddr != SWAPBLK_NONE)
swp_pager_freeswapspace(srcaddr, 1);
}
/*
* 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(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;
reqcount = count;
/*
* Determine the final number of read-behind pages and
* allocate them BEFORE releasing the object lock. Otherwise,
* there can be a problematic race with vm_object_split().
* Specifically, vm_object_split() might first transfer pages
* that precede ma[0] in the current object to a new object,
* and then this function incorrectly recreates those pages as
* read-behind pages in the current object.
*/
if (!swap_pager_haspage(object, ma[0]->pindex, &maxbehind, &maxahead))
return (VM_PAGER_FAIL);
/*
* Clip the readahead and readbehind ranges to exclude resident pages.
*/
if (rahead != NULL) {
KASSERT(reqcount - 1 <= maxahead,
("page count %d extends beyond swap block", reqcount));
*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_ctl(object, pindex, 0);
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);
/* 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);
while ((ma[0]->oflags & VPO_SWAPINPROG) != 0) {
ma[0]->oflags |= VPO_SWAPSLEEP;
VM_CNT_INC(v_intrans);
if (VM_OBJECT_SLEEP(object, &object->paging_in_progress, 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);
}
}
/*
* 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.
*/
}
/*
* 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);
VM_OBJECT_WUNLOCK(object);
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);
VM_OBJECT_WLOCK(object);
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 whos 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)
{
int i, n;
boolean_t sync;
daddr_t addr, n_free, s_free;
swp_pager_init_freerange(&s_free, &n_free);
if (count && ma[0]->object != object) {
panic("swap_pager_putpages: object mismatch %p/%p",
object,
ma[0]->object
);
}
/*
* Step 1
*
* Turn object into OBJT_SWAP
* check for bogus sysops
* force sync if not 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);
n = 0;
if (curproc != pageproc)
sync = TRUE;
else
sync = (flags & VM_PAGER_PUT_SYNC) != 0;
/*
* Step 2
*
* Assign swap blocks and issue I/O. We reallocate swap on the fly.
* The page is left dirty until the pageout operation completes
* successfully.
*/
for (i = 0; i < count; i += n) {
int j;
struct buf *bp;
daddr_t blk;
/* Maximum I/O size is limited by maximum swap block size. */
n = min(count - i, nsw_cluster_max);
/* Get a block of swap of size up to size n. */
blk = swp_pager_getswapspace(&n, 4);
if (blk == SWAPBLK_NONE) {
for (j = 0; j < n; ++j)
rtvals[i+j] = VM_PAGER_FAIL;
continue;
}
/*
* All I/O parameters have been satisfied, build the I/O
* request and assign the swap space.
*/
if (sync != TRUE) {
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);
}
bp = uma_zalloc(swwbuf_zone, M_WAITOK);
if (sync != TRUE)
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;
VM_OBJECT_WLOCK(object);
for (j = 0; j < n; ++j) {
vm_page_t mreq = ma[i+j];
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;
bp->b_pages[j] = mreq;
}
VM_OBJECT_WUNLOCK(object);
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 (sync == FALSE) {
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);
}
VM_OBJECT_WLOCK(object);
swp_pager_freeswapspace(s_free, n_free);
}
/*
* 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->paging_in_progress);
}
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.
*/
m->valid = 0;
} 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);
vm_page_lock(m);
vm_page_activate(m);
vm_page_unlock(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));
m->valid = VM_PAGE_BITS_ALL;
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_lock(m);
vm_page_deactivate_noreuse(m);
vm_page_unlock(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);
#ifdef INVARIANTS
vm_page_lock(m);
if (!vm_page_wired(m) && m->queue == PQ_NONE)
panic("page %p is neither wired nor queued", m);
vm_page_unlock(m);
#endif
vm_page_xunbusy(m);
swap_pager_unswapped(m);
}
static void
swp_pager_force_launder(vm_page_t m)
{
vm_page_dirty(m);
vm_page_lock(m);
vm_page_launder(m);
vm_page_unlock(m);
vm_page_xunbusy(m);
swap_pager_unswapped(m);
}
/*
* SWP_PAGER_FORCE_PAGEIN() - force swap blocks to be paged in
*
* This routine dissociates pages starting at the given index within an
* object from their backing store, paging them in if they do not reside
* in memory. Pages that are paged in are marked dirty and placed in the
* laundry queue. Pages are marked dirty because they no longer have
* backing store. They are placed in the laundry queue because they have
* not been accessed recently. Otherwise, they would already reside in
* memory.
*/
static void
swp_pager_force_pagein(vm_object_t object, vm_pindex_t pindex, int npages)
{
vm_page_t ma[npages];
int i, j;
KASSERT(npages > 0, ("%s: No pages", __func__));
KASSERT(npages <= MAXPHYS / PAGE_SIZE,
("%s: Too many pages: %d", __func__, npages));
vm_object_pip_add(object, npages);
vm_page_grab_pages(object, pindex, VM_ALLOC_NORMAL, ma, npages);
for (i = j = 0;; i++) {
/* Count nonresident pages, to page-in all at once. */
if (i < npages && ma[i]->valid != VM_PAGE_BITS_ALL)
continue;
if (j < i) {
/* Page-in nonresident pages. Mark for laundering. */
if (swap_pager_getpages(object, &ma[j], i - j, NULL,
NULL) != VM_PAGER_OK)
panic("%s: read from swap failed", __func__);
do {
swp_pager_force_launder(ma[j]);
} while (++j < i);
}
if (i == npages)
break;
/* Mark dirty a resident page. */
swp_pager_force_dirty(ma[j++]);
}
vm_object_pip_wakeupn(object, npages);
}
/*
* 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_pindex_t pi, s_pindex;
daddr_t blk, n_blks, s_blk;
int i;
n_blks = 0;
for (pi = 0; (sb = SWAP_PCTRIE_LOOKUP_GE(
&object->un_pager.swp.swp_blks, pi)) != NULL; ) {
for (i = 0; i < SWAP_META_PAGES; i++) {
blk = sb->d[i];
if (!swp_pager_isondev(blk, sp))
blk = SWAPBLK_NONE;
/*
* If there are no blocks/pages accumulated, start a new
* accumulation here.
*/
if (n_blks == 0) {
if (blk != SWAPBLK_NONE) {
s_blk = blk;
s_pindex = sb->p + i;
n_blks = 1;
}
continue;
}
/*
* If the accumulation can be extended without breaking
* the sequence of consecutive blocks and pages that
* swp_pager_force_pagein() depends on, do so.
*/
if (n_blks < MAXPHYS / PAGE_SIZE &&
s_blk + n_blks == blk &&
s_pindex + n_blks == sb->p + i) {
++n_blks;
continue;
}
/*
* The sequence of consecutive blocks and pages cannot
* be extended, so page them all in here. Then,
* because doing so involves releasing and reacquiring
* a lock that protects the swap block pctrie, do not
* rely on the current swap block. Break this loop and
* re-fetch the same pindex from the pctrie again.
*/
swp_pager_force_pagein(object, s_pindex, n_blks);
n_blks = 0;
break;
}
if (i == SWAP_META_PAGES)
pi = sb->p + SWAP_META_PAGES;
}
if (n_blks > 0)
swp_pager_force_pagein(object, s_pindex, n_blks);
}
/*
* 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_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;
KASSERT(object->handle == NULL, ("default pager with 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_swblk_empty(sb, 0, SWAP_META_PAGES)) {
SWAP_PCTRIE_REMOVE(&object->un_pager.swp.swp_blks, rdpi);
uma_zfree(swblk_zone, sb);
}
return (prev_swapblk);
}
/*
* 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)
{
struct swblk *sb;
daddr_t n_free, s_free;
vm_pindex_t last;
int i, limit, start;
VM_OBJECT_ASSERT_WLOCKED(object);
if (object->type != OBJT_SWAP || count == 0)
return;
swp_pager_init_freerange(&s_free, &n_free);
last = pindex + count;
for (;;) {
sb = SWAP_PCTRIE_LOOKUP_GE(&object->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;
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(&object->un_pager.swp.swp_blks,
sb->p);
uma_zfree(swblk_zone, sb);
}
}
swp_pager_freeswapspace(s_free, n_free);
}
/*
* 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.
*
* SWM_POP remove from meta data but do not free it
*/
static daddr_t
swp_pager_meta_ctl(vm_object_t object, vm_pindex_t pindex, int flags)
{
struct swblk *sb;
daddr_t r1;
if ((flags & SWM_POP) != 0)
VM_OBJECT_ASSERT_WLOCKED(object);
else
VM_OBJECT_ASSERT_LOCKED(object);
/*
* The meta data only exists if the object is OBJT_SWAP
* and even then might not be allocated yet.
*/
if (object->type != OBJT_SWAP)
return (SWAPBLK_NONE);
sb = SWAP_PCTRIE_LOOKUP(&object->un_pager.swp.swp_blks,
rounddown(pindex, SWAP_META_PAGES));
if (sb == NULL)
return (SWAPBLK_NONE);
r1 = sb->d[pindex % SWAP_META_PAGES];
if (r1 == SWAPBLK_NONE)
return (SWAPBLK_NONE);
if ((flags & SWM_POP) != 0) {
sb->d[pindex % SWAP_META_PAGES] = SWAPBLK_NONE;
if (swp_pager_swblk_empty(sb, 0, SWAP_META_PAGES)) {
SWAP_PCTRIE_REMOVE(&object->un_pager.swp.swp_blks,
rounddown(pindex, SWAP_META_PAGES));
uma_zfree(swblk_zone, sb);
}
}
return (r1);
}
/*
* 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(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)
{
unsigned long maxpages, npages;
npages = swap_total;
/* absolute maximum we can handle assuming 100% efficiency */
maxpages = uma_zone_get_max(swblk_zone) * SWAP_META_PAGES;
/* recommend using no more than half that amount */
if (npages > maxpages / 2) {
printf("warning: total configured swap (%lu pages) "
"exceeds maximum recommended amount (%lu pages).\n",
npages, 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;
swblk_t dvbase;
u_long 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);
/*
* 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 swap size to maximum of %luMB per unit\n",
mblocks / 1024 / 1024 * PAGE_SIZE);
nblks = mblocks;
}
sp = malloc(sizeof *sp, M_VMPGDATA, M_WAITOK | M_ZERO);
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;
sp->sw_blist = blist_create(nblks, M_WAITOK);
/*
* 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 - 2;
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, 0);
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, NULL))
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)
{
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);
}
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, NULL))
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;
for (cur = map->header.next; cur != &map->header; cur = cur->next) {
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 || (vp->v_iflag & VI_DOOMED) != 0) {
error = ENOENT;
} else {
g_topology_lock();
error = swapongeom_locked(vp->v_rdev, vp);
g_topology_unlock();
}
VOP_UNLOCK(vp, 0);
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, 0);
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);
}
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