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uvm_amap.c
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uvm_amap.c
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/* $NetBSD: uvm_amap.c,v 1.105.2.2 2012/04/09 18:13:11 riz 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.
*
* 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 1.105.2.2 2012/04/09 18:13:11 riz Exp $");
#include "opt_uvmhist.h"
#include <sys/param.h>
#include <sys/systm.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 allocation of the array fails
* (KM_NOSLEEP), 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: allocate an amap, but do not initialise the overlay.
*
* => Note: lock is not set.
*/
static struct vm_amap *
amap_alloc1(int slots, int padslots, int flags)
{
const bool nowait = (flags & UVM_FLAG_NOWAIT) != 0;
const km_flag_t kmflags = nowait ? KM_NOSLEEP : KM_SLEEP;
struct vm_amap *amap;
int totalslots;
amap = pool_cache_get(&uvm_amap_cache, nowait ? PR_NOWAIT : PR_WAITOK);
if (amap == NULL) {
return NULL;
}
totalslots = amap_roundup_slots(slots + padslots);
amap->am_lock = NULL;
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;
/*
* Note: since allocations are likely big, we expect to reduce the
* memory fragmentation by allocating them in separate blocks.
*/
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:
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 (nowait) {
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->am_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE);
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);
if (amap->am_lock != NULL) {
KASSERT(!mutex_owned(amap->am_lock));
mutex_obj_free(amap->am_lock);
}
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
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, *tofree;
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;
}
tofree = NULL;
/*
* 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, &tofree);
}
#endif
uvm_anon_freelst(amap, tofree);
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,
&tofree);
}
#endif
uvm_anon_freelst(amap, tofree);
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,
&tofree);
pp_setreflen(amap->am_ppref, amap->am_nslot, 1,
slotneed - amap->am_nslot);
}
#endif
amap->am_nslot = slotneed;
uvm_anon_freelst(amap, tofree);
/*
* 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 allocate a new amap and copy all the amap
* data over from old amap to the new one. Drop the lock before
* performing allocation.
*
* Note: since allocations are likely big, we expect to reduce the
* memory fragmentation by allocating them in separate blocks.
*/
amap_unlock(amap);
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) {
/* Will be handled later if fails. */
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);
/*
* Copy everything over to new allocated 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,
&tofree);
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;
uvm_anon_freelst(amap, tofree);
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;
u_int slots, lcv, slot, stop;
struct vm_anon *anon;
KASSERT(mutex_owned(amap->am_lock));
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++) {
anon = amap->am_anon[lcv];
if (anon == NULL) {
continue;
}
if (anon->an_page) {
pmap_page_protect(anon->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;
}
anon = amap->am_anon[slot];
if (anon->an_page) {
pmap_page_protect(anon->an_page, prot);
}
}
}
/*
* amap_wipeout: wipeout all anon's in an amap; then free the amap!
*
* => Called from amap_unref(), when reference count drops to zero.
* => amap must be locked.
*/
void
amap_wipeout(struct vm_amap *amap)
{
struct vm_anon *tofree = NULL;
u_int lcv;
UVMHIST_FUNC("amap_wipeout"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist,"(amap=0x%x)", amap, 0,0,0);
KASSERT(mutex_owned(amap->am_lock));
KASSERT(amap->am_ref == 0);
if (__predict_false(amap->am_flags & AMAP_SWAPOFF)) {
/*
* Note: amap_swap_off() will call us again.
*/
amap_unlock(amap);
return;
}
amap_list_remove(amap);
for (lcv = 0 ; lcv < amap->am_nused ; lcv++) {
struct vm_anon *anon;
u_int slot;
slot = amap->am_slots[lcv];
anon = amap->am_anon[slot];
KASSERT(anon != NULL && anon->an_ref != 0);
KASSERT(anon->an_lock == amap->am_lock);
UVMHIST_LOG(maphist," processing anon 0x%x, ref=%d", anon,
anon->an_ref, 0, 0);
/*
* Drop the reference. Defer freeing.
*/
if (--anon->an_ref == 0) {
anon->an_link = tofree;
tofree = anon;
}
if (curlwp->l_cpu->ci_schedstate.spc_flags & SPCF_SHOULDYIELD) {
preempt();
}
}
/*
* Finally, destroy the amap.
*/
amap->am_nused = 0;
uvm_anon_freelst(amap, tofree);
amap_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)
{
const int waitf = (flags & AMAP_COPY_NOWAIT) ? UVM_FLAG_NOWAIT : 0;
struct vm_amap *amap, *srcamap;
struct vm_anon *tofree;
u_int slots, lcv;
vsize_t len;
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 */
srcamap = entry->aref.ar_amap;
len = entry->end - entry->start;
/*
* Is there an amap to copy? If not, create one.
*/
if (srcamap == NULL) {
const bool canchunk = (flags & AMAP_COPY_NOCHUNK) == 0;
/*
* 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(len) >= UVM_AMAP_LARGE) {
vsize_t chunksize;
/* 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);
/* Watch out for endva wrap-around! */
if (endva >= startva) {
UVM_MAP_CLIP_END(map, entry, endva);
}
}
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);
/*
* Allocate an initialised amap and install it.
* Note: we must update the length after clipping.
*/
len = entry->end - entry->start;
entry->aref.ar_pageoff = 0;
entry->aref.ar_amap = amap_alloc(len, 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
* he amap we currently have. If so, then just take it over instead
* of copying it. Note that we are reading am_ref without lock held
* as the value value can only be one if we have the only reference
* to the amap (via our locked map). If the value is greater than
* one, then allocate amap and re-check the value.
*/
if (srcamap->am_ref == 1) {
entry->etype &= ~UVM_ET_NEEDSCOPY;
UVMHIST_LOG(maphist, "<- done [ref cnt = 1, took it over]",
0, 0, 0, 0);
return;
}
UVMHIST_LOG(maphist," amap=%p, ref=%d, must copy it",
srcamap, srcamap->am_ref, 0, 0);
/*
* Allocate a new amap (note: not initialised, no lock set, etc).
*/
AMAP_B2SLOT(slots, len);
amap = amap_alloc1(slots, 0, waitf);
if (amap == NULL) {
UVMHIST_LOG(maphist, " amap_alloc1 failed", 0,0,0,0);
return;
}
amap_lock(srcamap);
/*
* Re-check the reference count with the lock held. If it has
* dropped to one - we can take over the existing map.
*/
if (srcamap->am_ref == 1) {
/* Just take over the existing amap. */
entry->etype &= ~UVM_ET_NEEDSCOPY;
amap_unlock(srcamap);
/* Destroy the new (unused) amap. */
amap->am_ref--;
amap_free(amap);
return;
}
/*
* Copy the slots. Zero the padded part.
*/
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;
KASSERT(amap->am_anon[lcv]->an_lock == srcamap->am_lock);
KASSERT(amap->am_anon[lcv]->an_ref > 0);
KASSERT(amap->am_nused < amap->am_maxslot);
amap->am_anon[lcv]->an_ref++;
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.
* Since the reference count on srcamap is greater than one,
* (we checked above), it cannot drop to zero while it is locked.
*/
srcamap->am_ref--;
KASSERT(srcamap->am_ref > 0);
if (srcamap->am_ref == 1 && (srcamap->am_flags & AMAP_SHARED) != 0) {
srcamap->am_flags &= ~AMAP_SHARED;
}
tofree = NULL;
#ifdef UVM_AMAP_PPREF
if (srcamap->am_ppref && srcamap->am_ppref != PPREF_NONE) {
amap_pp_adjref(srcamap, entry->aref.ar_pageoff,
len >> PAGE_SHIFT, -1, &tofree);
}
#endif
/*
* If we referenced any anons, then share the source amap's lock.
* Otherwise, we have nothing in common, so allocate a new one.
*/
KASSERT(amap->am_lock == NULL);
if (amap->am_nused != 0) {
amap->am_lock = srcamap->am_lock;
mutex_obj_hold(amap->am_lock);
}
uvm_anon_freelst(srcamap, tofree);
if (amap->am_lock == NULL) {
amap->am_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE);
}
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;
struct vm_anon *anon, *nanon;
struct vm_page *pg, *npg;
u_int lcv, slot;
/*
* 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++) {
slot = amap->am_slots[lcv];
anon = amap->am_anon[slot];
KASSERT(anon->an_lock == amap->am_lock);
/*
* If anon has only one reference - 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 is not wired.
*/
if (anon->an_ref == 1) {
KASSERT(anon->an_page != NULL || anon->an_swslot != 0);
continue;
}