NetBSD-5.0.2/sys/uvm/uvm_amap.c
/* $NetBSD: uvm_amap.c,v 1.84.20.1 2009/02/02 19:24:04 snj Exp $ */
/*
*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
* All rights reserved.
*
* 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 Charles D. Cranor and
* Washington University.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/
/*
* uvm_amap.c: amap operations
*/
/*
* this file contains functions that perform operations on amaps. see
* uvm_amap.h for a brief explanation of the role of amaps in uvm.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_amap.c,v 1.84.20.1 2009/02/02 19:24:04 snj Exp $");
#include "opt_uvmhist.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/kmem.h>
#include <sys/pool.h>
#include <sys/atomic.h>
#include <uvm/uvm.h>
#include <uvm/uvm_swap.h>
/*
* cache for allocation of vm_map structures. note that in order to
* avoid an endless loop, the amap cache's allocator cannot allocate
* memory from an amap (it currently goes through the kernel uobj, so
* we are ok).
*/
static struct pool_cache uvm_amap_cache;
static kmutex_t amap_list_lock;
static LIST_HEAD(, vm_amap) amap_list;
/*
* local functions
*/
static inline void
amap_list_insert(struct vm_amap *amap)
{
mutex_enter(&amap_list_lock);
LIST_INSERT_HEAD(&amap_list, amap, am_list);
mutex_exit(&amap_list_lock);
}
static inline void
amap_list_remove(struct vm_amap *amap)
{
mutex_enter(&amap_list_lock);
LIST_REMOVE(amap, am_list);
mutex_exit(&amap_list_lock);
}
static int
amap_roundup_slots(int slots)
{
return kmem_roundup_size(slots * sizeof(int)) / sizeof(int);
}
#ifdef UVM_AMAP_PPREF
/*
* what is ppref? ppref is an _optional_ amap feature which is used
* to keep track of reference counts on a per-page basis. it is enabled
* when UVM_AMAP_PPREF is defined.
*
* when enabled, an array of ints is allocated for the pprefs. this
* array is allocated only when a partial reference is added to the
* map (either by unmapping part of the amap, or gaining a reference
* to only a part of an amap). if the malloc of the array fails
* (M_NOWAIT), then we set the array pointer to PPREF_NONE to indicate
* that we tried to do ppref's but couldn't alloc the array so just
* give up (after all, this is an optional feature!).
*
* the array is divided into page sized "chunks." for chunks of length 1,
* the chunk reference count plus one is stored in that chunk's slot.
* for chunks of length > 1 the first slot contains (the reference count
* plus one) * -1. [the negative value indicates that the length is
* greater than one.] the second slot of the chunk contains the length
* of the chunk. here is an example:
*
* actual REFS: 2 2 2 2 3 1 1 0 0 0 4 4 0 1 1 1
* ppref: -3 4 x x 4 -2 2 -1 3 x -5 2 1 -2 3 x
* <----------><-><----><-------><----><-><------->
* (x = don't care)
*
* this allows us to allow one int to contain the ref count for the whole
* chunk. note that the "plus one" part is needed because a reference
* count of zero is neither positive or negative (need a way to tell
* if we've got one zero or a bunch of them).
*
* here are some in-line functions to help us.
*/
/*
* pp_getreflen: get the reference and length for a specific offset
*
* => ppref's amap must be locked
*/
static inline void
pp_getreflen(int *ppref, int offset, int *refp, int *lenp)
{
if (ppref[offset] > 0) { /* chunk size must be 1 */
*refp = ppref[offset] - 1; /* don't forget to adjust */
*lenp = 1;
} else {
*refp = (ppref[offset] * -1) - 1;
*lenp = ppref[offset+1];
}
}
/*
* pp_setreflen: set the reference and length for a specific offset
*
* => ppref's amap must be locked
*/
static inline void
pp_setreflen(int *ppref, int offset, int ref, int len)
{
if (len == 0)
return;
if (len == 1) {
ppref[offset] = ref + 1;
} else {
ppref[offset] = (ref + 1) * -1;
ppref[offset+1] = len;
}
}
#endif /* UVM_AMAP_PPREF */
/*
* amap_alloc1: internal function that allocates an amap, but does not
* init the overlay.
*
* => lock on returned amap is init'd
*/
static inline struct vm_amap *
amap_alloc1(int slots, int padslots, int waitf)
{
struct vm_amap *amap;
int totalslots;
km_flag_t kmflags;
amap = pool_cache_get(&uvm_amap_cache,
((waitf & UVM_FLAG_NOWAIT) != 0) ? PR_NOWAIT : PR_WAITOK);
if (amap == NULL)
return(NULL);
kmflags = ((waitf & UVM_FLAG_NOWAIT) != 0) ? KM_NOSLEEP : KM_SLEEP;
totalslots = amap_roundup_slots(slots + padslots);
mutex_init(&amap->am_l, MUTEX_DEFAULT, IPL_NONE);
amap->am_ref = 1;
amap->am_flags = 0;
#ifdef UVM_AMAP_PPREF
amap->am_ppref = NULL;
#endif
amap->am_maxslot = totalslots;
amap->am_nslot = slots;
amap->am_nused = 0;
amap->am_slots = kmem_alloc(totalslots * sizeof(int), kmflags);
if (amap->am_slots == NULL)
goto fail1;
amap->am_bckptr = kmem_alloc(totalslots * sizeof(int), kmflags);
if (amap->am_bckptr == NULL)
goto fail2;
amap->am_anon = kmem_alloc(totalslots * sizeof(struct vm_anon *),
kmflags);
if (amap->am_anon == NULL)
goto fail3;
return(amap);
fail3:
kmem_free(amap->am_bckptr, totalslots * sizeof(int));
fail2:
kmem_free(amap->am_slots, totalslots * sizeof(int));
fail1:
mutex_destroy(&amap->am_l);
pool_cache_put(&uvm_amap_cache, amap);
/*
* XXX hack to tell the pagedaemon how many pages we need,
* since we can need more than it would normally free.
*/
if ((waitf & UVM_FLAG_NOWAIT) != 0) {
extern u_int uvm_extrapages;
atomic_add_int(&uvm_extrapages,
((sizeof(int) * 2 + sizeof(struct vm_anon *)) *
totalslots) >> PAGE_SHIFT);
}
return (NULL);
}
/*
* amap_alloc: allocate an amap to manage "sz" bytes of anonymous VM
*
* => caller should ensure sz is a multiple of PAGE_SIZE
* => reference count to new amap is set to one
* => new amap is returned unlocked
*/
struct vm_amap *
amap_alloc(vaddr_t sz, vaddr_t padsz, int waitf)
{
struct vm_amap *amap;
int slots, padslots;
UVMHIST_FUNC("amap_alloc"); UVMHIST_CALLED(maphist);
AMAP_B2SLOT(slots, sz);
AMAP_B2SLOT(padslots, padsz);
amap = amap_alloc1(slots, padslots, waitf);
if (amap) {
memset(amap->am_anon, 0,
amap->am_maxslot * sizeof(struct vm_anon *));
amap_list_insert(amap);
}
UVMHIST_LOG(maphist,"<- done, amap = 0x%x, sz=%d", amap, sz, 0, 0);
return(amap);
}
/*
* uvm_amap_init: initialize the amap system.
*/
void
uvm_amap_init(void)
{
mutex_init(&amap_list_lock, MUTEX_DEFAULT, IPL_NONE);
pool_cache_bootstrap(&uvm_amap_cache, sizeof(struct vm_amap), 0, 0, 0,
"amappl", NULL, IPL_NONE, NULL, NULL, NULL);
}
/*
* amap_free: free an amap
*
* => the amap must be unlocked
* => the amap should have a zero reference count and be empty
*/
void
amap_free(struct vm_amap *amap)
{
int slots;
UVMHIST_FUNC("amap_free"); UVMHIST_CALLED(maphist);
KASSERT(amap->am_ref == 0 && amap->am_nused == 0);
KASSERT((amap->am_flags & AMAP_SWAPOFF) == 0);
KASSERT(!mutex_owned(&amap->am_l));
slots = amap->am_maxslot;
kmem_free(amap->am_slots, slots * sizeof(*amap->am_slots));
kmem_free(amap->am_bckptr, slots * sizeof(*amap->am_bckptr));
kmem_free(amap->am_anon, slots * sizeof(*amap->am_anon));
#ifdef UVM_AMAP_PPREF
if (amap->am_ppref && amap->am_ppref != PPREF_NONE)
kmem_free(amap->am_ppref, slots * sizeof(*amap->am_ppref));
#endif
mutex_destroy(&amap->am_l);
pool_cache_put(&uvm_amap_cache, amap);
UVMHIST_LOG(maphist,"<- done, freed amap = 0x%x", amap, 0, 0, 0);
}
/*
* amap_extend: extend the size of an amap (if needed)
*
* => called from uvm_map when we want to extend an amap to cover
* a new mapping (rather than allocate a new one)
* => amap should be unlocked (we will lock it)
* => to safely extend an amap it should have a reference count of
* one (thus it can't be shared)
*/
int
amap_extend(struct vm_map_entry *entry, vsize_t addsize, int flags)
{
struct vm_amap *amap = entry->aref.ar_amap;
int slotoff = entry->aref.ar_pageoff;
int slotmapped, slotadd, slotneed, slotadded, slotalloc;
int slotadj, slotspace;
int oldnslots;
#ifdef UVM_AMAP_PPREF
int *newppref, *oldppref;
#endif
int i, *newsl, *newbck, *oldsl, *oldbck;
struct vm_anon **newover, **oldover;
const km_flag_t kmflags =
(flags & AMAP_EXTEND_NOWAIT) ? KM_NOSLEEP : KM_SLEEP;
UVMHIST_FUNC("amap_extend"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist, " (entry=0x%x, addsize=0x%x, flags=0x%x)",
entry, addsize, flags, 0);
/*
* first, determine how many slots we need in the amap. don't
* forget that ar_pageoff could be non-zero: this means that
* there are some unused slots before us in the amap.
*/
amap_lock(amap);
KASSERT(amap_refs(amap) == 1); /* amap can't be shared */
AMAP_B2SLOT(slotmapped, entry->end - entry->start); /* slots mapped */
AMAP_B2SLOT(slotadd, addsize); /* slots to add */
if (flags & AMAP_EXTEND_FORWARDS) {
slotneed = slotoff + slotmapped + slotadd;
slotadj = 0;
slotspace = 0;
}
else {
slotneed = slotadd + slotmapped;
slotadj = slotadd - slotoff;
slotspace = amap->am_maxslot - slotmapped;
}
/*
* case 1: we already have enough slots in the map and thus
* only need to bump the reference counts on the slots we are
* adding.
*/
if (flags & AMAP_EXTEND_FORWARDS) {
if (amap->am_nslot >= slotneed) {
#ifdef UVM_AMAP_PPREF
if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
amap_pp_adjref(amap, slotoff + slotmapped,
slotadd, 1);
}
#endif
amap_unlock(amap);
UVMHIST_LOG(maphist,
"<- done (case 1f), amap = 0x%x, sltneed=%d",
amap, slotneed, 0, 0);
return 0;
}
} else {
if (slotadj <= 0) {
slotoff -= slotadd;
entry->aref.ar_pageoff = slotoff;
#ifdef UVM_AMAP_PPREF
if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
amap_pp_adjref(amap, slotoff, slotadd, 1);
}
#endif
amap_unlock(amap);
UVMHIST_LOG(maphist,
"<- done (case 1b), amap = 0x%x, sltneed=%d",
amap, slotneed, 0, 0);
return 0;
}
}
/*
* case 2: we pre-allocated slots for use and we just need to
* bump nslot up to take account for these slots.
*/
if (amap->am_maxslot >= slotneed) {
if (flags & AMAP_EXTEND_FORWARDS) {
#ifdef UVM_AMAP_PPREF
if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
if ((slotoff + slotmapped) < amap->am_nslot)
amap_pp_adjref(amap,
slotoff + slotmapped,
(amap->am_nslot -
(slotoff + slotmapped)), 1);
pp_setreflen(amap->am_ppref, amap->am_nslot, 1,
slotneed - amap->am_nslot);
}
#endif
amap->am_nslot = slotneed;
amap_unlock(amap);
/*
* no need to zero am_anon since that was done at
* alloc time and we never shrink an allocation.
*/
UVMHIST_LOG(maphist,"<- done (case 2f), amap = 0x%x, "
"slotneed=%d", amap, slotneed, 0, 0);
return 0;
} else {
#ifdef UVM_AMAP_PPREF
if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
/*
* Slide up the ref counts on the pages that
* are actually in use.
*/
memmove(amap->am_ppref + slotspace,
amap->am_ppref + slotoff,
slotmapped * sizeof(int));
/*
* Mark the (adjusted) gap at the front as
* referenced/not referenced.
*/
pp_setreflen(amap->am_ppref,
0, 0, slotspace - slotadd);
pp_setreflen(amap->am_ppref,
slotspace - slotadd, 1, slotadd);
}
#endif
/*
* Slide the anon pointers up and clear out
* the space we just made.
*/
memmove(amap->am_anon + slotspace,
amap->am_anon + slotoff,
slotmapped * sizeof(struct vm_anon*));
memset(amap->am_anon + slotoff, 0,
(slotspace - slotoff) * sizeof(struct vm_anon *));
/*
* Slide the backpointers up, but don't bother
* wiping out the old slots.
*/
memmove(amap->am_bckptr + slotspace,
amap->am_bckptr + slotoff,
slotmapped * sizeof(int));
/*
* Adjust all the useful active slot numbers.
*/
for (i = 0; i < amap->am_nused; i++)
amap->am_slots[i] += (slotspace - slotoff);
/*
* We just filled all the empty space in the
* front of the amap by activating a few new
* slots.
*/
amap->am_nslot = amap->am_maxslot;
entry->aref.ar_pageoff = slotspace - slotadd;
amap_unlock(amap);
UVMHIST_LOG(maphist,"<- done (case 2b), amap = 0x%x, "
"slotneed=%d", amap, slotneed, 0, 0);
return 0;
}
}
/*
* case 3: we need to malloc a new amap and copy all the amap
* data over from old amap to the new one.
*
* note that the use of a kernel realloc() probably would not
* help here, since we wish to abort cleanly if one of the
* three (or four) mallocs fails.
*/
amap_unlock(amap); /* unlock in case we sleep in malloc */
if (slotneed >= UVM_AMAP_LARGE) {
return E2BIG;
}
slotalloc = amap_roundup_slots(slotneed);
#ifdef UVM_AMAP_PPREF
newppref = NULL;
if (amap->am_ppref && amap->am_ppref != PPREF_NONE)
newppref = kmem_alloc(slotalloc * sizeof(*newppref), kmflags);
#endif
newsl = kmem_alloc(slotalloc * sizeof(*newsl), kmflags);
newbck = kmem_alloc(slotalloc * sizeof(*newbck), kmflags);
newover = kmem_alloc(slotalloc * sizeof(*newover), kmflags);
if (newsl == NULL || newbck == NULL || newover == NULL) {
#ifdef UVM_AMAP_PPREF
if (newppref != NULL) {
kmem_free(newppref, slotalloc * sizeof(*newppref));
}
#endif
if (newsl != NULL) {
kmem_free(newsl, slotalloc * sizeof(*newsl));
}
if (newbck != NULL) {
kmem_free(newbck, slotalloc * sizeof(*newbck));
}
if (newover != NULL) {
kmem_free(newover, slotalloc * sizeof(*newover));
}
return ENOMEM;
}
amap_lock(amap);
KASSERT(amap->am_maxslot < slotneed);
/*
* now copy everything over to new malloc'd areas...
*/
slotadded = slotalloc - amap->am_nslot;
if (!(flags & AMAP_EXTEND_FORWARDS))
slotspace = slotalloc - slotmapped;
/* do am_slots */
oldsl = amap->am_slots;
if (flags & AMAP_EXTEND_FORWARDS)
memcpy(newsl, oldsl, sizeof(int) * amap->am_nused);
else
for (i = 0; i < amap->am_nused; i++)
newsl[i] = oldsl[i] + slotspace - slotoff;
amap->am_slots = newsl;
/* do am_anon */
oldover = amap->am_anon;
if (flags & AMAP_EXTEND_FORWARDS) {
memcpy(newover, oldover,
sizeof(struct vm_anon *) * amap->am_nslot);
memset(newover + amap->am_nslot, 0,
sizeof(struct vm_anon *) * slotadded);
} else {
memcpy(newover + slotspace, oldover + slotoff,
sizeof(struct vm_anon *) * slotmapped);
memset(newover, 0,
sizeof(struct vm_anon *) * slotspace);
}
amap->am_anon = newover;
/* do am_bckptr */
oldbck = amap->am_bckptr;
if (flags & AMAP_EXTEND_FORWARDS)
memcpy(newbck, oldbck, sizeof(int) * amap->am_nslot);
else
memcpy(newbck + slotspace, oldbck + slotoff,
sizeof(int) * slotmapped);
amap->am_bckptr = newbck;
#ifdef UVM_AMAP_PPREF
/* do ppref */
oldppref = amap->am_ppref;
if (newppref) {
if (flags & AMAP_EXTEND_FORWARDS) {
memcpy(newppref, oldppref,
sizeof(int) * amap->am_nslot);
memset(newppref + amap->am_nslot, 0,
sizeof(int) * slotadded);
} else {
memcpy(newppref + slotspace, oldppref + slotoff,
sizeof(int) * slotmapped);
}
amap->am_ppref = newppref;
if ((flags & AMAP_EXTEND_FORWARDS) &&
(slotoff + slotmapped) < amap->am_nslot)
amap_pp_adjref(amap, slotoff + slotmapped,
(amap->am_nslot - (slotoff + slotmapped)), 1);
if (flags & AMAP_EXTEND_FORWARDS)
pp_setreflen(newppref, amap->am_nslot, 1,
slotneed - amap->am_nslot);
else {
pp_setreflen(newppref, 0, 0,
slotalloc - slotneed);
pp_setreflen(newppref, slotalloc - slotneed, 1,
slotneed - slotmapped);
}
} else {
if (amap->am_ppref)
amap->am_ppref = PPREF_NONE;
}
#endif
/* update master values */
if (flags & AMAP_EXTEND_FORWARDS)
amap->am_nslot = slotneed;
else {
entry->aref.ar_pageoff = slotspace - slotadd;
amap->am_nslot = slotalloc;
}
oldnslots = amap->am_maxslot;
amap->am_maxslot = slotalloc;
amap_unlock(amap);
kmem_free(oldsl, oldnslots * sizeof(*oldsl));
kmem_free(oldbck, oldnslots * sizeof(*oldbck));
kmem_free(oldover, oldnslots * sizeof(*oldover));
#ifdef UVM_AMAP_PPREF
if (oldppref && oldppref != PPREF_NONE)
kmem_free(oldppref, oldnslots * sizeof(*oldppref));
#endif
UVMHIST_LOG(maphist,"<- done (case 3), amap = 0x%x, slotneed=%d",
amap, slotneed, 0, 0);
return 0;
}
/*
* amap_share_protect: change protection of anons in a shared amap
*
* for shared amaps, given the current data structure layout, it is
* not possible for us to directly locate all maps referencing the
* shared anon (to change the protection). in order to protect data
* in shared maps we use pmap_page_protect(). [this is useful for IPC
* mechanisms like map entry passing that may want to write-protect
* all mappings of a shared amap.] we traverse am_anon or am_slots
* depending on the current state of the amap.
*
* => entry's map and amap must be locked by the caller
*/
void
amap_share_protect(struct vm_map_entry *entry, vm_prot_t prot)
{
struct vm_amap *amap = entry->aref.ar_amap;
int slots, lcv, slot, stop;
KASSERT(mutex_owned(&amap->am_l));
AMAP_B2SLOT(slots, (entry->end - entry->start));
stop = entry->aref.ar_pageoff + slots;
if (slots < amap->am_nused) {
/* cheaper to traverse am_anon */
for (lcv = entry->aref.ar_pageoff ; lcv < stop ; lcv++) {
if (amap->am_anon[lcv] == NULL)
continue;
if (amap->am_anon[lcv]->an_page != NULL)
pmap_page_protect(amap->am_anon[lcv]->an_page,
prot);
}
return;
}
/* cheaper to traverse am_slots */
for (lcv = 0 ; lcv < amap->am_nused ; lcv++) {
slot = amap->am_slots[lcv];
if (slot < entry->aref.ar_pageoff || slot >= stop)
continue;
if (amap->am_anon[slot]->an_page != NULL)
pmap_page_protect(amap->am_anon[slot]->an_page, prot);
}
}
/*
* amap_wipeout: wipeout all anon's in an amap; then free the amap!
*
* => called from amap_unref when the final reference to an amap is
* discarded (i.e. when reference count drops to 0)
* => the amap should be locked (by the caller)
*/
void
amap_wipeout(struct vm_amap *amap)
{
int lcv, slot;
struct vm_anon *anon;
UVMHIST_FUNC("amap_wipeout"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist,"(amap=0x%x)", amap, 0,0,0);
KASSERT(amap->am_ref == 0);
if (__predict_false((amap->am_flags & AMAP_SWAPOFF) != 0)) {
/*
* amap_swap_off will call us again.
*/
amap_unlock(amap);
return;
}
amap_list_remove(amap);
amap_unlock(amap);
for (lcv = 0 ; lcv < amap->am_nused ; lcv++) {
int refs;
slot = amap->am_slots[lcv];
anon = amap->am_anon[slot];
if (anon == NULL || anon->an_ref == 0)
panic("amap_wipeout: corrupt amap");
mutex_enter(&anon->an_lock);
UVMHIST_LOG(maphist," processing anon 0x%x, ref=%d", anon,
anon->an_ref, 0, 0);
refs = --anon->an_ref;
mutex_exit(&anon->an_lock);
if (refs == 0) {
/*
* we had the last reference to a vm_anon. free it.
*/
uvm_anfree(anon);
}
if (curlwp->l_cpu->ci_schedstate.spc_flags & SPCF_SHOULDYIELD)
preempt();
}
/*
* now we free the map
*/
amap->am_nused = 0;
amap_free(amap); /* will unlock and free amap */
UVMHIST_LOG(maphist,"<- done!", 0,0,0,0);
}
/*
* amap_copy: ensure that a map entry's "needs_copy" flag is false
* by copying the amap if necessary.
*
* => an entry with a null amap pointer will get a new (blank) one.
* => the map that the map entry belongs to must be locked by caller.
* => the amap currently attached to "entry" (if any) must be unlocked.
* => if canchunk is true, then we may clip the entry into a chunk
* => "startva" and "endva" are used only if canchunk is true. they are
* used to limit chunking (e.g. if you have a large space that you
* know you are going to need to allocate amaps for, there is no point
* in allowing that to be chunked)
*/
void
amap_copy(struct vm_map *map, struct vm_map_entry *entry, int flags,
vaddr_t startva, vaddr_t endva)
{
struct vm_amap *amap, *srcamap;
int slots, lcv;
vaddr_t chunksize;
const int waitf = (flags & AMAP_COPY_NOWAIT) ? UVM_FLAG_NOWAIT : 0;
const bool canchunk = (flags & AMAP_COPY_NOCHUNK) == 0;
UVMHIST_FUNC("amap_copy"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist, " (map=%p, entry=%p, flags=%d)",
map, entry, flags, 0);
KASSERT(map != kernel_map); /* we use nointr pool */
/*
* is there a map to copy? if not, create one from scratch.
*/
if (entry->aref.ar_amap == NULL) {
/*
* check to see if we have a large amap that we can
* chunk. we align startva/endva to chunk-sized
* boundaries and then clip to them.
*/
if (canchunk && atop(entry->end - entry->start) >=
UVM_AMAP_LARGE) {
/* convert slots to bytes */
chunksize = UVM_AMAP_CHUNK << PAGE_SHIFT;
startva = (startva / chunksize) * chunksize;
endva = roundup(endva, chunksize);
UVMHIST_LOG(maphist, " chunk amap ==> clip 0x%x->0x%x"
"to 0x%x->0x%x", entry->start, entry->end, startva,
endva);
UVM_MAP_CLIP_START(map, entry, startva, NULL);
/* watch out for endva wrap-around! */
if (endva >= startva)
UVM_MAP_CLIP_END(map, entry, endva, NULL);
}
if ((flags & AMAP_COPY_NOMERGE) == 0 &&
uvm_mapent_trymerge(map, entry, UVM_MERGE_COPYING)) {
return;
}
UVMHIST_LOG(maphist, "<- done [creating new amap 0x%x->0x%x]",
entry->start, entry->end, 0, 0);
entry->aref.ar_pageoff = 0;
entry->aref.ar_amap = amap_alloc(entry->end - entry->start, 0,
waitf);
if (entry->aref.ar_amap != NULL)
entry->etype &= ~UVM_ET_NEEDSCOPY;
return;
}
/*
* first check and see if we are the only map entry
* referencing the amap we currently have. if so, then we can
* just take it over rather than copying it. note that we are
* reading am_ref with the amap unlocked... the value can only
* be one if we have the only reference to the amap (via our
* locked map). if we are greater than one we fall through to
* the next case (where we double check the value).
*/
if (entry->aref.ar_amap->am_ref == 1) {
entry->etype &= ~UVM_ET_NEEDSCOPY;
UVMHIST_LOG(maphist, "<- done [ref cnt = 1, took it over]",
0, 0, 0, 0);
return;
}
/*
* looks like we need to copy the map.
*/
UVMHIST_LOG(maphist," amap=%p, ref=%d, must copy it",
entry->aref.ar_amap, entry->aref.ar_amap->am_ref, 0, 0);
AMAP_B2SLOT(slots, entry->end - entry->start);
amap = amap_alloc1(slots, 0, waitf);
if (amap == NULL) {
UVMHIST_LOG(maphist, " amap_alloc1 failed", 0,0,0,0);
return;
}
srcamap = entry->aref.ar_amap;
amap_lock(srcamap);
/*
* need to double check reference count now that we've got the
* src amap locked down. the reference count could have
* changed while we were in malloc. if the reference count
* dropped down to one we take over the old map rather than
* copying the amap.
*/
if (srcamap->am_ref == 1) { /* take it over? */
entry->etype &= ~UVM_ET_NEEDSCOPY;
amap->am_ref--; /* drop final reference to map */
amap_free(amap); /* dispose of new (unused) amap */
amap_unlock(srcamap);
return;
}
/*
* we must copy it now.
*/
UVMHIST_LOG(maphist, " copying amap now",0, 0, 0, 0);
for (lcv = 0 ; lcv < slots; lcv++) {
amap->am_anon[lcv] =
srcamap->am_anon[entry->aref.ar_pageoff + lcv];
if (amap->am_anon[lcv] == NULL)
continue;
mutex_enter(&amap->am_anon[lcv]->an_lock);
amap->am_anon[lcv]->an_ref++;
mutex_exit(&amap->am_anon[lcv]->an_lock);
amap->am_bckptr[lcv] = amap->am_nused;
amap->am_slots[amap->am_nused] = lcv;
amap->am_nused++;
}
memset(&amap->am_anon[lcv], 0,
(amap->am_maxslot - lcv) * sizeof(struct vm_anon *));
/*
* drop our reference to the old amap (srcamap) and unlock.
* we know that the reference count on srcamap is greater than
* one (we checked above), so there is no way we could drop
* the count to zero. [and no need to worry about freeing it]
*/
srcamap->am_ref--;
if (srcamap->am_ref == 1 && (srcamap->am_flags & AMAP_SHARED) != 0)
srcamap->am_flags &= ~AMAP_SHARED; /* clear shared flag */
#ifdef UVM_AMAP_PPREF
if (srcamap->am_ppref && srcamap->am_ppref != PPREF_NONE) {
amap_pp_adjref(srcamap, entry->aref.ar_pageoff,
(entry->end - entry->start) >> PAGE_SHIFT, -1);
}
#endif
amap_unlock(srcamap);
amap_list_insert(amap);
/*
* install new amap.
*/
entry->aref.ar_pageoff = 0;
entry->aref.ar_amap = amap;
entry->etype &= ~UVM_ET_NEEDSCOPY;
UVMHIST_LOG(maphist, "<- done",0, 0, 0, 0);
}
/*
* amap_cow_now: resolve all copy-on-write faults in an amap now for fork(2)
*
* called during fork(2) when the parent process has a wired map
* entry. in that case we want to avoid write-protecting pages
* in the parent's map (e.g. like what you'd do for a COW page)
* so we resolve the COW here.
*
* => assume parent's entry was wired, thus all pages are resident.
* => assume pages that are loaned out (loan_count) are already mapped
* read-only in all maps, and thus no need for us to worry about them
* => assume both parent and child vm_map's are locked
* => caller passes child's map/entry in to us
* => if we run out of memory we will unlock the amap and sleep _with_ the
* parent and child vm_map's locked(!). we have to do this since
* we are in the middle of a fork(2) and we can't let the parent
* map change until we are done copying all the map entrys.
* => XXXCDC: out of memory should cause fork to fail, but there is
* currently no easy way to do this (needs fix)
* => page queues must be unlocked (we may lock them)
*/
void
amap_cow_now(struct vm_map *map, struct vm_map_entry *entry)
{
struct vm_amap *amap = entry->aref.ar_amap;
int lcv, slot;
struct vm_anon *anon, *nanon;
struct vm_page *pg, *npg;
/*
* note that if we unlock the amap then we must ReStart the "lcv" for
* loop because some other process could reorder the anon's in the
* am_anon[] array on us while the lock is dropped.
*/
ReStart:
amap_lock(amap);
for (lcv = 0 ; lcv < amap->am_nused ; lcv++) {
/*
* get the page
*/
slot = amap->am_slots[lcv];
anon = amap->am_anon[slot];
mutex_enter(&anon->an_lock);
/*
* If the anon has only one ref, we must have already copied it.
* This can happen if we needed to sleep waiting for memory
* in a previous run through this loop. The new page might
* even have been paged out, since the new page is not wired.
*/
if (anon->an_ref == 1) {
KASSERT(anon->an_page != NULL || anon->an_swslot != 0);
mutex_exit(&anon->an_lock);
continue;
}
/*
* The old page must be resident since the parent is wired.
*/
pg = anon->an_page;
KASSERT(pg != NULL);
KASSERT(pg->wire_count > 0);
/*
* If the page is loaned then it must already be mapped
* read-only and we don't need to copy it.
*/
if (pg->loan_count != 0) {
mutex_exit(&anon->an_lock);
continue;
}
KASSERT(pg->uanon == anon && pg->uobject == NULL);
/*
* if the page is busy then we have to unlock, wait for
* it and then restart.
*/
if (pg->flags & PG_BUSY) {
pg->flags |= PG_WANTED;
amap_unlock(amap);
UVM_UNLOCK_AND_WAIT(pg, &anon->an_lock, false,
"cownow", 0);
goto ReStart;
}
/*
* ok, time to do a copy-on-write to a new anon
*/
nanon = uvm_analloc();
if (nanon) {
npg = uvm_pagealloc(NULL, 0, nanon, 0);
} else
npg = NULL; /* XXX: quiet gcc warning */
if (nanon == NULL || npg == NULL) {
/*
* XXXCDC: we should cause fork to fail, but we can't.
*/
if (nanon) {
nanon->an_ref--;
mutex_exit(&nanon->an_lock);
uvm_anfree(nanon);
}
mutex_exit(&anon->an_lock);
amap_unlock(amap);
uvm_wait("cownowpage");
goto ReStart;
}
/*
* got it... now we can copy the data and replace anon
* with our new one...
*/
uvm_pagecopy(pg, npg); /* old -> new */
anon->an_ref--; /* can't drop to zero */
amap->am_anon[slot] = nanon; /* replace */
/*
* drop PG_BUSY on new page ... since we have had its owner
* locked the whole time it can't be PG_RELEASED or PG_WANTED.
*/
mutex_enter(&uvm_pageqlock);
uvm_pageactivate(npg);
mutex_exit(&uvm_pageqlock);
npg->flags &= ~(PG_BUSY|PG_FAKE);
UVM_PAGE_OWN(npg, NULL);
mutex_exit(&nanon->an_lock);
mutex_exit(&anon->an_lock);
}
amap_unlock(amap);
}
/*
* amap_splitref: split a single reference into two separate references
*
* => called from uvm_map's clip routines
* => origref's map should be locked
* => origref->ar_amap should be unlocked (we will lock)
*/
void
amap_splitref(struct vm_aref *origref, struct vm_aref *splitref, vaddr_t offset)
{
int leftslots;
struct vm_amap *amap;
KASSERT(splitref->ar_amap == origref->ar_amap);
AMAP_B2SLOT(leftslots, offset);
if (leftslots == 0)
panic("amap_splitref: split at zero offset");
amap = origref->ar_amap;
amap_lock(amap);
/*
* now: amap is locked and we have a valid am_mapped array.
*/
if (amap->am_nslot - origref->ar_pageoff - leftslots <= 0)
panic("amap_splitref: map size check failed");
#ifdef UVM_AMAP_PPREF
/*
* establish ppref before we add a duplicate reference to the amap
*/
if (amap->am_ppref == NULL)
amap_pp_establish(amap, origref->ar_pageoff);
#endif
amap->am_ref++; /* not a share reference */
splitref->ar_pageoff = origref->ar_pageoff + leftslots;
amap_unlock(amap);
}
#ifdef UVM_AMAP_PPREF
/*
* amap_pp_establish: add a ppref array to an amap, if possible
*
* => amap locked by caller
*/
void
amap_pp_establish(struct vm_amap *amap, vaddr_t offset)
{
amap->am_ppref = kmem_alloc(amap->am_maxslot * sizeof(*amap->am_ppref),
KM_NOSLEEP);
/*
* if we fail then we just won't use ppref for this amap
*/
if (amap->am_ppref == NULL) {
amap->am_ppref = PPREF_NONE; /* not using it */
return;
}
memset(amap->am_ppref, 0, sizeof(int) * amap->am_maxslot);
pp_setreflen(amap->am_ppref, 0, 0, offset);
pp_setreflen(amap->am_ppref, offset, amap->am_ref,
amap->am_nslot - offset);
return;
}
/*
* amap_pp_adjref: adjust reference count to a part of an amap using the
* per-page reference count array.
*
* => map and amap locked by caller
* => caller must check that ppref != PPREF_NONE before calling
*/
void
amap_pp_adjref(struct vm_amap *amap, int curslot, vsize_t slotlen, int adjval)
{
int stopslot, *ppref, lcv, prevlcv;
int ref, len, prevref, prevlen;
stopslot = curslot + slotlen;
ppref = amap->am_ppref;
prevlcv = 0;
/*
* first advance to the correct place in the ppref array,
* fragment if needed.
*/
for (lcv = 0 ; lcv < curslot ; lcv += len) {
pp_getreflen(ppref, lcv, &ref, &len);
if (lcv + len > curslot) { /* goes past start? */
pp_setreflen(ppref, lcv, ref, curslot - lcv);
pp_setreflen(ppref, curslot, ref, len - (curslot -lcv));
len = curslot - lcv; /* new length of entry @ lcv */
}
prevlcv = lcv;
}
if (lcv != 0)
pp_getreflen(ppref, prevlcv, &prevref, &prevlen);
else {
/* Ensure that the "prevref == ref" test below always
* fails, since we're starting from the beginning of
* the ppref array; that is, there is no previous
* chunk.
*/
prevref = -1;
prevlen = 0;
}
/*
* now adjust reference counts in range. merge the first
* changed entry with the last unchanged entry if possible.
*/
if (lcv != curslot)
panic("amap_pp_adjref: overshot target");
for (/* lcv already set */; lcv < stopslot ; lcv += len) {
pp_getreflen(ppref, lcv, &ref, &len);
if (lcv + len > stopslot) { /* goes past end? */
pp_setreflen(ppref, lcv, ref, stopslot - lcv);
pp_setreflen(ppref, stopslot, ref,
len - (stopslot - lcv));
len = stopslot - lcv;
}
ref += adjval;
if (ref < 0)
panic("amap_pp_adjref: negative reference count");
if (lcv == prevlcv + prevlen && ref == prevref) {
pp_setreflen(ppref, prevlcv, ref, prevlen + len);
} else {
pp_setreflen(ppref, lcv, ref, len);
}
if (ref == 0)
amap_wiperange(amap, lcv, len);
}
}
/*
* amap_wiperange: wipe out a range of an amap
* [different from amap_wipeout because the amap is kept intact]
*
* => both map and amap must be locked by caller.
*/
void
amap_wiperange(struct vm_amap *amap, int slotoff, int slots)
{
int byanon, lcv, stop, curslot, ptr, slotend;
struct vm_anon *anon;
/*
* we can either traverse the amap by am_anon or by am_slots depending
* on which is cheaper. decide now.
*/
if (slots < amap->am_nused) {
byanon = true;
lcv = slotoff;
stop = slotoff + slots;
slotend = 0;
} else {
byanon = false;
lcv = 0;
stop = amap->am_nused;
slotend = slotoff + slots;
}
while (lcv < stop) {
int refs;
if (byanon) {
curslot = lcv++; /* lcv advances here */
if (amap->am_anon[curslot] == NULL)
continue;
} else {
curslot = amap->am_slots[lcv];
if (curslot < slotoff || curslot >= slotend) {
lcv++; /* lcv advances here */
continue;
}
stop--; /* drop stop, since anon will be removed */
}
anon = amap->am_anon[curslot];
/*
* remove it from the amap
*/
amap->am_anon[curslot] = NULL;
ptr = amap->am_bckptr[curslot];
if (ptr != (amap->am_nused - 1)) {
amap->am_slots[ptr] =
amap->am_slots[amap->am_nused - 1];
amap->am_bckptr[amap->am_slots[ptr]] =
ptr; /* back ptr. */
}
amap->am_nused--;
/*
* drop anon reference count
*/
mutex_enter(&anon->an_lock);
refs = --anon->an_ref;
mutex_exit(&anon->an_lock);
if (refs == 0) {
/*
* we just eliminated the last reference to an anon.
* free it.
*/
uvm_anfree(anon);
}
}
}
#endif
#if defined(VMSWAP)
/*
* amap_swap_off: pagein anonymous pages in amaps and drop swap slots.
*
* => called with swap_syscall_lock held.
* => note that we don't always traverse all anons.
* eg. amaps being wiped out, released anons.
* => return true if failed.
*/
bool
amap_swap_off(int startslot, int endslot)
{
struct vm_amap *am;
struct vm_amap *am_next;
struct vm_amap marker_prev;
struct vm_amap marker_next;
struct lwp *l = curlwp;
bool rv = false;
#if defined(DIAGNOSTIC)
memset(&marker_prev, 0, sizeof(marker_prev));
memset(&marker_next, 0, sizeof(marker_next));
#endif /* defined(DIAGNOSTIC) */
uvm_lwp_hold(l);
mutex_enter(&amap_list_lock);
for (am = LIST_FIRST(&amap_list); am != NULL && !rv; am = am_next) {
int i;
LIST_INSERT_BEFORE(am, &marker_prev, am_list);
LIST_INSERT_AFTER(am, &marker_next, am_list);
if (!amap_lock_try(am)) {
mutex_exit(&amap_list_lock);
preempt();
mutex_enter(&amap_list_lock);
am_next = LIST_NEXT(&marker_prev, am_list);
if (am_next == &marker_next) {
am_next = LIST_NEXT(am_next, am_list);
} else {
KASSERT(LIST_NEXT(am_next, am_list) ==
&marker_next);
}
LIST_REMOVE(&marker_prev, am_list);
LIST_REMOVE(&marker_next, am_list);
continue;
}
mutex_exit(&amap_list_lock);
if (am->am_nused <= 0) {
amap_unlock(am);
goto next;
}
for (i = 0; i < am->am_nused; i++) {
int slot;
int swslot;
struct vm_anon *anon;
slot = am->am_slots[i];
anon = am->am_anon[slot];
mutex_enter(&anon->an_lock);
swslot = anon->an_swslot;
if (swslot < startslot || endslot <= swslot) {
mutex_exit(&anon->an_lock);
continue;
}
am->am_flags |= AMAP_SWAPOFF;
amap_unlock(am);
rv = uvm_anon_pagein(anon);
amap_lock(am);
am->am_flags &= ~AMAP_SWAPOFF;
if (amap_refs(am) == 0) {
amap_wipeout(am);
am = NULL;
break;
}
if (rv) {
break;
}
i = 0;
}
if (am) {
amap_unlock(am);
}
next:
mutex_enter(&amap_list_lock);
KASSERT(LIST_NEXT(&marker_prev, am_list) == &marker_next ||
LIST_NEXT(LIST_NEXT(&marker_prev, am_list), am_list) ==
&marker_next);
am_next = LIST_NEXT(&marker_next, am_list);
LIST_REMOVE(&marker_prev, am_list);
LIST_REMOVE(&marker_next, am_list);
}
mutex_exit(&amap_list_lock);
uvm_lwp_rele(l);
return rv;
}
#endif /* defined(VMSWAP) */
/*
* amap_lookup: look up a page in an amap
*
* => amap should be locked by caller.
*/
struct vm_anon *
amap_lookup(struct vm_aref *aref, vaddr_t offset)
{
int slot;
struct vm_amap *amap = aref->ar_amap;
UVMHIST_FUNC("amap_lookup"); UVMHIST_CALLED(maphist);
KASSERT(mutex_owned(&amap->am_l));
AMAP_B2SLOT(slot, offset);
slot += aref->ar_pageoff;
if (slot >= amap->am_nslot)
panic("amap_lookup: offset out of range");
UVMHIST_LOG(maphist, "<- done (amap=0x%x, offset=0x%x, result=0x%x)",
amap, offset, amap->am_anon[slot], 0);
return(amap->am_anon[slot]);
}
/*
* amap_lookups: look up a range of pages in an amap
*
* => amap should be locked by caller.
* => XXXCDC: this interface is biased toward array-based amaps. fix.
*/
void
amap_lookups(struct vm_aref *aref, vaddr_t offset, struct vm_anon **anons,
int npages)
{
int slot;
struct vm_amap *amap = aref->ar_amap;
UVMHIST_FUNC("amap_lookups"); UVMHIST_CALLED(maphist);
KASSERT(mutex_owned(&amap->am_l));
AMAP_B2SLOT(slot, offset);
slot += aref->ar_pageoff;
UVMHIST_LOG(maphist, " slot=%d, npages=%d, nslot=%d", slot, npages,
amap->am_nslot, 0);
if ((slot + (npages - 1)) >= amap->am_nslot)
panic("amap_lookups: offset out of range");
memcpy(anons, &amap->am_anon[slot], npages * sizeof(struct vm_anon *));
UVMHIST_LOG(maphist, "<- done", 0, 0, 0, 0);
return;
}
/*
* amap_add: add (or replace) a page to an amap
*
* => caller must lock amap.
* => if (replace) caller must lock anon because we might have to call
* pmap_page_protect on the anon's page.
*/
void
amap_add(struct vm_aref *aref, vaddr_t offset, struct vm_anon *anon,
bool replace)
{
int slot;
struct vm_amap *amap = aref->ar_amap;
UVMHIST_FUNC("amap_add"); UVMHIST_CALLED(maphist);
KASSERT(mutex_owned(&amap->am_l));
AMAP_B2SLOT(slot, offset);
slot += aref->ar_pageoff;
if (slot >= amap->am_nslot)
panic("amap_add: offset out of range");
if (replace) {
if (amap->am_anon[slot] == NULL)
panic("amap_add: replacing null anon");
if (amap->am_anon[slot]->an_page != NULL &&
(amap->am_flags & AMAP_SHARED) != 0) {
pmap_page_protect(amap->am_anon[slot]->an_page,
VM_PROT_NONE);
/*
* XXX: suppose page is supposed to be wired somewhere?
*/
}
} else { /* !replace */
if (amap->am_anon[slot] != NULL)
panic("amap_add: slot in use");
amap->am_bckptr[slot] = amap->am_nused;
amap->am_slots[amap->am_nused] = slot;
amap->am_nused++;
}
amap->am_anon[slot] = anon;
UVMHIST_LOG(maphist,
"<- done (amap=0x%x, offset=0x%x, anon=0x%x, rep=%d)",
amap, offset, anon, replace);
}
/*
* amap_unadd: remove a page from an amap
*
* => caller must lock amap
*/
void
amap_unadd(struct vm_aref *aref, vaddr_t offset)
{
int ptr, slot;
struct vm_amap *amap = aref->ar_amap;
UVMHIST_FUNC("amap_unadd"); UVMHIST_CALLED(maphist);
KASSERT(mutex_owned(&amap->am_l));
AMAP_B2SLOT(slot, offset);
slot += aref->ar_pageoff;
if (slot >= amap->am_nslot)
panic("amap_unadd: offset out of range");
if (amap->am_anon[slot] == NULL)
panic("amap_unadd: nothing there");
amap->am_anon[slot] = NULL;
ptr = amap->am_bckptr[slot];
if (ptr != (amap->am_nused - 1)) { /* swap to keep slots contig? */
amap->am_slots[ptr] = amap->am_slots[amap->am_nused - 1];
amap->am_bckptr[amap->am_slots[ptr]] = ptr; /* back link */
}
amap->am_nused--;
UVMHIST_LOG(maphist, "<- done (amap=0x%x, slot=0x%x)", amap, slot,0, 0);
}
/*
* amap_ref: gain a reference to an amap
*
* => amap must not be locked (we will lock)
* => "offset" and "len" are in units of pages
* => called at fork time to gain the child's reference
*/
void
amap_ref(struct vm_amap *amap, vaddr_t offset, vsize_t len, int flags)
{
UVMHIST_FUNC("amap_ref"); UVMHIST_CALLED(maphist);
amap_lock(amap);
if (flags & AMAP_SHARED)
amap->am_flags |= AMAP_SHARED;
#ifdef UVM_AMAP_PPREF
if (amap->am_ppref == NULL && (flags & AMAP_REFALL) == 0 &&
len != amap->am_nslot)
amap_pp_establish(amap, offset);
#endif
amap->am_ref++;
#ifdef UVM_AMAP_PPREF
if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
if (flags & AMAP_REFALL)
amap_pp_adjref(amap, 0, amap->am_nslot, 1);
else
amap_pp_adjref(amap, offset, len, 1);
}
#endif
amap_unlock(amap);
UVMHIST_LOG(maphist,"<- done! amap=0x%x", amap, 0, 0, 0);
}
/*
* amap_unref: remove a reference to an amap
*
* => caller must remove all pmap-level references to this amap before
* dropping the reference
* => called from uvm_unmap_detach [only] ... note that entry is no
* longer part of a map and thus has no need for locking
* => amap must be unlocked (we will lock it).
*/
void
amap_unref(struct vm_amap *amap, vaddr_t offset, vsize_t len, bool all)
{
UVMHIST_FUNC("amap_unref"); UVMHIST_CALLED(maphist);
/*
* lock it
*/
amap_lock(amap);
UVMHIST_LOG(maphist," amap=0x%x refs=%d, nused=%d",
amap, amap->am_ref, amap->am_nused, 0);
KASSERT(amap_refs(amap) > 0);
/*
* if we are the last reference, free the amap and return.
*/
amap->am_ref--;
if (amap_refs(amap) == 0) {
amap_wipeout(amap); /* drops final ref and frees */
UVMHIST_LOG(maphist,"<- done (was last ref)!", 0, 0, 0, 0);
return; /* no need to unlock */
}
/*
* otherwise just drop the reference count(s)
*/
if (amap_refs(amap) == 1 && (amap->am_flags & AMAP_SHARED) != 0)
amap->am_flags &= ~AMAP_SHARED; /* clear shared flag */
#ifdef UVM_AMAP_PPREF
if (amap->am_ppref == NULL && all == 0 && len != amap->am_nslot)
amap_pp_establish(amap, offset);
if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
if (all)
amap_pp_adjref(amap, 0, amap->am_nslot, -1);
else
amap_pp_adjref(amap, offset, len, -1);
}
#endif
amap_unlock(amap);
UVMHIST_LOG(maphist,"<- done!", 0, 0, 0, 0);
}