File: [local] / sys / uvm / uvm_amap.c (download)
Revision 1.1, Tue Mar 4 16:15:20 2008 UTC (16 years, 1 month ago) by nbrk
Branch point for: MAIN
Initial revision
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/* $OpenBSD: uvm_amap.c,v 1.39 2007/06/18 21:51:15 pedro Exp $ */
/* $NetBSD: uvm_amap.c,v 1.27 2000/11/25 06:27:59 chs 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.
*/
#undef UVM_AMAP_INLINE /* enable/disable amap inlines */
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/kernel.h>
#include <sys/pool.h>
#define UVM_AMAP_C /* ensure disabled inlines are in */
#include <uvm/uvm.h>
#include <uvm/uvm_swap.h>
/*
* pool for allocation of vm_map structures. note that the pool has
* its own simplelock for its protection. also note that in order to
* avoid an endless loop, the amap pool's allocator cannot allocate
* memory from an amap (it currently goes through the kernel uobj, so
* we are ok).
*/
struct pool uvm_amap_pool;
LIST_HEAD(, vm_amap) amap_list;
/*
* local functions
*/
static struct vm_amap *amap_alloc1(int, int, int);
static __inline void amap_list_insert(struct vm_amap *);
static __inline void amap_list_remove(struct vm_amap *);
static __inline void
amap_list_insert(struct vm_amap *amap)
{
LIST_INSERT_HEAD(&amap_list, amap, am_list);
}
static __inline void
amap_list_remove(struct vm_amap *amap)
{
LIST_REMOVE(amap, am_list);
}
#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.
*/
static __inline void pp_getreflen(int *, int, int *, int *);
static __inline void pp_setreflen(int *, int, int, int);
/*
* 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 == 1) {
ppref[offset] = ref + 1;
} else {
ppref[offset] = (ref + 1) * -1;
ppref[offset+1] = len;
}
}
#endif
/*
* amap_init: called at boot time to init global amap data structures
*/
void
amap_init(void)
{
/*
* Initialize the vm_amap pool.
*/
pool_init(&uvm_amap_pool, sizeof(struct vm_amap), 0, 0, 0,
"amappl", &pool_allocator_nointr);
pool_sethiwat(&uvm_amap_pool, 4096);
}
/*
* 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;
amap = pool_get(&uvm_amap_pool, (waitf == M_WAITOK) ? PR_WAITOK : 0);
if (amap == NULL)
return(NULL);
totalslots = malloc_roundup((slots + padslots) * sizeof(int)) /
sizeof(int);
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 = malloc(totalslots * sizeof(int), M_UVMAMAP,
waitf);
if (amap->am_slots == NULL)
goto fail1;
amap->am_bckptr = malloc(totalslots * sizeof(int), M_UVMAMAP, waitf);
if (amap->am_bckptr == NULL)
goto fail2;
amap->am_anon = malloc(totalslots * sizeof(struct vm_anon *),
M_UVMAMAP, waitf);
if (amap->am_anon == NULL)
goto fail3;
return(amap);
fail3:
free(amap->am_bckptr, M_UVMAMAP);
fail2:
free(amap->am_slots, M_UVMAMAP);
fail1:
pool_put(&uvm_amap_pool, amap);
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); /* load slots */
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 = %p, sz=%lu", amap, sz, 0, 0);
return(amap);
}
/*
* amap_free: free an amap
*
* => the amap must be locked (mainly for simplelock accounting)
* => the amap should have a zero reference count and be empty
*/
void
amap_free(struct vm_amap *amap)
{
UVMHIST_FUNC("amap_free"); UVMHIST_CALLED(maphist);
KASSERT(amap->am_ref == 0 && amap->am_nused == 0);
KASSERT((amap->am_flags & AMAP_SWAPOFF) == 0);
free(amap->am_slots, M_UVMAMAP);
free(amap->am_bckptr, M_UVMAMAP);
free(amap->am_anon, M_UVMAMAP);
#ifdef UVM_AMAP_PPREF
if (amap->am_ppref && amap->am_ppref != PPREF_NONE)
free(amap->am_ppref, M_UVMAMAP);
#endif
pool_put(&uvm_amap_pool, amap);
UVMHIST_LOG(maphist,"<- done, freed amap = %p", 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)
* => XXXCDC: support padding at this level?
*/
int
amap_extend(struct vm_map_entry *entry, vsize_t addsize)
{
struct vm_amap *amap = entry->aref.ar_amap;
int slotoff = entry->aref.ar_pageoff;
int slotmapped, slotadd, slotneed, slotalloc;
#ifdef UVM_AMAP_PPREF
int *newppref, *oldppref;
#endif
u_int *newsl, *newbck, *oldsl, *oldbck;
struct vm_anon **newover, **oldover;
int slotadded;
UVMHIST_FUNC("amap_extend"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist, " (entry=%p, addsize=%lu)", entry, addsize, 0, 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_B2SLOT(slotmapped, entry->end - entry->start); /* slots mapped */
AMAP_B2SLOT(slotadd, addsize); /* slots to add */
slotneed = slotoff + slotmapped + slotadd;
/*
* 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 (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
UVMHIST_LOG(maphist,"<- done (case 1), amap = %p, sltneed=%ld",
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) {
#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;
/*
* no need to zero am_anon since that was done at
* alloc time and we never shrink an allocation.
*/
UVMHIST_LOG(maphist,"<- done (case 2), amap = %p, slotneed=%ld",
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.
*
* XXXCDC: could we take advantage of a kernel realloc()?
*/
slotalloc = malloc_roundup(slotneed * sizeof(int)) / sizeof(int);
#ifdef UVM_AMAP_PPREF
newppref = NULL;
if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
newppref = malloc(slotalloc *sizeof(int), M_UVMAMAP,
M_WAITOK | M_CANFAIL);
if (newppref == NULL) {
/* give up if malloc fails */
free(amap->am_ppref, M_UVMAMAP);
amap->am_ppref = PPREF_NONE;
}
}
#endif
newsl = malloc(slotalloc * sizeof(int), M_UVMAMAP,
M_WAITOK | M_CANFAIL);
newbck = malloc(slotalloc * sizeof(int), M_UVMAMAP,
M_WAITOK | M_CANFAIL);
newover = malloc(slotalloc * sizeof(struct vm_anon *), M_UVMAMAP,
M_WAITOK | M_CANFAIL);
if (newsl == NULL || newbck == NULL || newover == NULL) {
if (newsl != NULL) {
free(newsl, M_UVMAMAP);
}
if (newbck != NULL) {
free(newbck, M_UVMAMAP);
}
if (newover != NULL) {
free(newover, M_UVMAMAP);
}
return (ENOMEM);
}
KASSERT(amap->am_maxslot < slotneed);
/*
* now copy everything over to new malloc'd areas...
*/
slotadded = slotalloc - amap->am_nslot;
/* do am_slots */
oldsl = amap->am_slots;
memcpy(newsl, oldsl, sizeof(int) * amap->am_nused);
amap->am_slots = newsl;
/* do am_anon */
oldover = amap->am_anon;
memcpy(newover, oldover, sizeof(struct vm_anon *) * amap->am_nslot);
memset(newover + amap->am_nslot, 0, sizeof(struct vm_anon *) *
slotadded);
amap->am_anon = newover;
/* do am_bckptr */
oldbck = amap->am_bckptr;
memcpy(newbck, oldbck, sizeof(int) * amap->am_nslot);
memset(newbck + amap->am_nslot, 0, sizeof(int) * slotadded); /* XXX: needed? */
amap->am_bckptr = newbck;
#ifdef UVM_AMAP_PPREF
/* do ppref */
oldppref = amap->am_ppref;
if (newppref) {
memcpy(newppref, oldppref, sizeof(int) * amap->am_nslot);
memset(newppref + amap->am_nslot, 0, sizeof(int) * slotadded);
amap->am_ppref = newppref;
if ((slotoff + slotmapped) < amap->am_nslot)
amap_pp_adjref(amap, slotoff + slotmapped,
(amap->am_nslot - (slotoff + slotmapped)), 1);
pp_setreflen(newppref, amap->am_nslot, 1,
slotneed - amap->am_nslot);
}
#endif
/* update master values */
amap->am_nslot = slotneed;
amap->am_maxslot = slotalloc;
/* and free */
free(oldsl, M_UVMAMAP);
free(oldbck, M_UVMAMAP);
free(oldover, M_UVMAMAP);
#ifdef UVM_AMAP_PPREF
if (oldppref && oldppref != PPREF_NONE)
free(oldppref, M_UVMAMAP);
#endif
UVMHIST_LOG(maphist,"<- done (case 3), amap = %p, slotneed=%ld",
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;
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);
}
return;
}
/*
* 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 == 1)
* => 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=%p)", 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.
*/
return;
}
amap_list_remove(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");
simple_lock(&anon->an_lock); /* lock anon */
UVMHIST_LOG(maphist," processing anon %p, ref=%ld", anon,
anon->an_ref, 0, 0);
refs = --anon->an_ref;
simple_unlock(&anon->an_lock);
if (refs == 0) {
/*
* we had the last reference to a vm_anon. free it.
*/
uvm_anfree(anon);
}
}
/*
* now we free the map
*/
amap->am_ref = 0; /* ... was one */
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 waitf,
boolean_t canchunk, vaddr_t startva, vaddr_t endva)
{
struct vm_amap *amap, *srcamap;
int slots, lcv;
vaddr_t chunksize;
UVMHIST_FUNC("amap_copy"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist, " (map=%p, entry=%p, waitf=%ld)",
map, entry, waitf, 0);
/*
* 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%lx->0x%lx to 0x%lx->0x%lx",
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);
}
UVMHIST_LOG(maphist, "<- done [creating new amap 0x%lx->0x%lx]",
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=%ld, 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;
/*
* 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 */
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;
simple_lock(&amap->am_anon[lcv]->an_lock);
amap->am_anon[lcv]->an_ref++;
simple_unlock(&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
/*
* install new amap.
*/
entry->aref.ar_pageoff = 0;
entry->aref.ar_amap = amap;
entry->etype &= ~UVM_ET_NEEDSCOPY;
amap_list_insert(amap);
/*
* done!
*/
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 entries.
* => 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:
for (lcv = 0 ; lcv < amap->am_nused ; lcv++) {
/*
* get the page
*/
slot = amap->am_slots[lcv];
anon = amap->am_anon[slot];
simple_lock(&anon->an_lock);
pg = anon->an_page;
/*
* page must be resident since parent is wired
*/
if (pg == NULL)
panic("amap_cow_now: non-resident wired page in anon %p",
anon);
/*
* if the anon ref count is one and the page is not loaned,
* then we are safe (the child has exclusive access to the
* page). if the page is loaned, then it must already be
* mapped read-only.
*
* we only need to get involved when these are not true.
* [note: if loan_count == 0, then the anon must own the page]
*/
if (anon->an_ref > 1 && pg->loan_count == 0) {
/*
* if the page is busy then we have to unlock, wait for
* it and then restart.
*/
if (pg->pg_flags & PG_BUSY) {
atomic_setbits_int(&pg->pg_flags, PG_WANTED);
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) {
/* out of memory */
/*
* XXXCDC: we should cause fork to fail, but
* we can't ...
*/
if (nanon) {
simple_lock(&nanon->an_lock);
uvm_anfree(nanon);
}
simple_unlock(&anon->an_lock);
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 it's
* owner locked the whole time it can't be
* PG_RELEASED | PG_WANTED.
*/
atomic_clearbits_int(&npg->pg_flags, PG_BUSY|PG_FAKE);
UVM_PAGE_OWN(npg, NULL);
uvm_lock_pageq();
uvm_pageactivate(npg);
uvm_unlock_pageq();
}
simple_unlock(&anon->an_lock);
/*
* done with this anon, next ...!
*/
} /* end of 'for' loop */
}
/*
* 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;
AMAP_B2SLOT(leftslots, offset);
if (leftslots == 0)
panic("amap_splitref: split at zero offset");
/*
* now: amap is locked and we have a valid am_mapped array.
*/
if (origref->ar_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 (origref->ar_amap->am_ppref == NULL)
amap_pp_establish(origref->ar_amap);
#endif
splitref->ar_amap = origref->ar_amap;
splitref->ar_amap->am_ref++; /* not a share reference */
splitref->ar_pageoff = origref->ar_pageoff + leftslots;
}
#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)
{
amap->am_ppref = malloc(sizeof(int) * amap->am_maxslot,
M_UVMAMAP, M_NOWAIT);
/*
* 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;
}
/*
* init ppref
*/
memset(amap->am_ppref, 0, sizeof(int) * amap->am_maxslot);
pp_setreflen(amap->am_ppref, 0, amap->am_ref, amap->am_nslot);
}
/*
* 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;
} 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
*/
simple_lock(&anon->an_lock);
refs = --anon->an_ref;
simple_unlock(&anon->an_lock);
if (refs == 0) {
/*
* we just eliminated the last reference to an anon.
* free it.
*/
uvm_anfree(anon);
}
}
}
#endif
/*
* 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.
*/
boolean_t
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;
boolean_t rv = FALSE;
#if defined(DIAGNOSTIC)
memset(&marker_prev, 0, sizeof(marker_prev));
memset(&marker_next, 0, sizeof(marker_next));
#endif /* defined(DIAGNOSTIC) */
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 (am->am_nused <= 0) {
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];
simple_lock(&anon->an_lock);
swslot = anon->an_swslot;
if (swslot < startslot || endslot <= swslot) {
simple_unlock(&anon->an_lock);
continue;
}
am->am_flags |= AMAP_SWAPOFF;
rv = uvm_anon_pagein(anon);
am->am_flags &= ~AMAP_SWAPOFF;
if (amap_refs(am) == 0) {
amap_wipeout(am);
am = NULL;
break;
}
if (rv) {
break;
}
i = 0;
}
next:
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);
}
return rv;
}
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