/* $NetBSD: uvm_aobj.c,v 1.157 2023/02/24 11:03:13 riastradh Exp $ */
/*
* Copyright (c) 1998 Chuck Silvers, 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.
*
* from: Id: uvm_aobj.c,v 1.1.2.5 1998/02/06 05:14:38 chs Exp
*/
/*
* uvm_aobj.c: anonymous memory uvm_object pager
*
* author: Chuck Silvers <chuq@chuq.com>
* started: Jan-1998
*
* - design mostly from Chuck Cranor
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_aobj.c,v 1.157 2023/02/24 11:03:13 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "opt_uvmhist.h"
#endif
#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_page_array.h>
/*
* An anonymous UVM object (aobj) manages anonymous-memory. In addition to
* keeping the list of resident pages, it may also keep a list of allocated
* swap blocks. Depending on the size of the object, this list is either
* stored in an array (small objects) or in a hash table (large objects).
*
* Lock order
*
* uao_list_lock ->
* uvm_object::vmobjlock
*/
/*
* Note: for hash tables, we break the address space of the aobj into blocks
* of UAO_SWHASH_CLUSTER_SIZE pages, which shall be a power of two.
*/
#define UAO_SWHASH_CLUSTER_SHIFT 4
#define UAO_SWHASH_CLUSTER_SIZE (1 << UAO_SWHASH_CLUSTER_SHIFT)
/* Get the "tag" for this page index. */
#define UAO_SWHASH_ELT_TAG(idx) ((idx) >> UAO_SWHASH_CLUSTER_SHIFT)
#define UAO_SWHASH_ELT_PAGESLOT_IDX(idx) \
((idx) & (UAO_SWHASH_CLUSTER_SIZE - 1))
/* Given an ELT and a page index, find the swap slot. */
#define UAO_SWHASH_ELT_PAGESLOT(elt, idx) \
((elt)->slots[UAO_SWHASH_ELT_PAGESLOT_IDX(idx)])
/* Given an ELT, return its pageidx base. */
#define UAO_SWHASH_ELT_PAGEIDX_BASE(ELT) \
((elt)->tag << UAO_SWHASH_CLUSTER_SHIFT)
/* The hash function. */
#define UAO_SWHASH_HASH(aobj, idx) \
(&(aobj)->u_swhash[(((idx) >> UAO_SWHASH_CLUSTER_SHIFT) \
& (aobj)->u_swhashmask)])
/*
* The threshold which determines whether we will use an array or a
* hash table to store the list of allocated swap blocks.
*/
#define UAO_SWHASH_THRESHOLD (UAO_SWHASH_CLUSTER_SIZE * 4)
#define UAO_USES_SWHASH(aobj) \
((aobj)->u_pages > UAO_SWHASH_THRESHOLD)
/* The number of buckets in a hash, with an upper bound. */
#define UAO_SWHASH_MAXBUCKETS 256
#define UAO_SWHASH_BUCKETS(aobj) \
(MIN((aobj)->u_pages >> UAO_SWHASH_CLUSTER_SHIFT, UAO_SWHASH_MAXBUCKETS))
/*
* uao_swhash_elt: when a hash table is being used, this structure defines
* the format of an entry in the bucket list.
*/
struct uao_swhash_elt {
LIST_ENTRY(uao_swhash_elt) list; /* the hash list */
voff_t tag; /* our 'tag' */
int count; /* our number of active slots */
int slots[UAO_SWHASH_CLUSTER_SIZE]; /* the slots */
};
/*
* uao_swhash: the swap hash table structure
*/
LIST_HEAD(uao_swhash, uao_swhash_elt);
/*
* uao_swhash_elt_pool: pool of uao_swhash_elt structures.
* Note: pages for this pool must not come from a pageable kernel map.
*/
static struct pool uao_swhash_elt_pool __cacheline_aligned;
/*
* uvm_aobj: the actual anon-backed uvm_object
*
* => the uvm_object is at the top of the structure, this allows
* (struct uvm_aobj *) == (struct uvm_object *)
* => only one of u_swslots and u_swhash is used in any given aobj
*/
struct uvm_aobj {
struct uvm_object u_obj; /* has: lock, pgops, #pages, #refs */
pgoff_t u_pages; /* number of pages in entire object */
int u_flags; /* the flags (see uvm_aobj.h) */
int *u_swslots; /* array of offset->swapslot mappings */
/*
* hashtable of offset->swapslot mappings
* (u_swhash is an array of bucket heads)
*/
struct uao_swhash *u_swhash;
u_long u_swhashmask; /* mask for hashtable */
LIST_ENTRY(uvm_aobj) u_list; /* global list of aobjs */
int u_freelist; /* freelist to allocate pages from */
};
static void uao_free(struct uvm_aobj *);
static int uao_get(struct uvm_object *, voff_t, struct vm_page **,
int *, int, vm_prot_t, int, int);
static int uao_put(struct uvm_object *, voff_t, voff_t, int);
#if defined(VMSWAP)
static struct uao_swhash_elt *uao_find_swhash_elt
(struct uvm_aobj *, int, bool);
static bool uao_pagein(struct uvm_aobj *, int, int);
static bool uao_pagein_page(struct uvm_aobj *, int);
#endif /* defined(VMSWAP) */
static struct vm_page *uao_pagealloc(struct uvm_object *, voff_t, int);
/*
* aobj_pager
*
* note that some functions (e.g. put) are handled elsewhere
*/
const struct uvm_pagerops aobj_pager = {
.pgo_reference = uao_reference,
.pgo_detach = uao_detach,
.pgo_get = uao_get,
.pgo_put = uao_put,
};
/*
* uao_list: global list of active aobjs, locked by uao_list_lock
*/
static LIST_HEAD(aobjlist, uvm_aobj) uao_list __cacheline_aligned;
static kmutex_t uao_list_lock __cacheline_aligned;
/*
* hash table/array related functions
*/
#if defined(VMSWAP)
/*
* uao_find_swhash_elt: find (or create) a hash table entry for a page
* offset.
*
* => the object should be locked by the caller
*/
static struct uao_swhash_elt *
uao_find_swhash_elt(struct uvm_aobj *aobj, int pageidx, bool create)
{
struct uao_swhash *swhash;
struct uao_swhash_elt *elt;
voff_t page_tag;
swhash = UAO_SWHASH_HASH(aobj, pageidx);
page_tag = UAO_SWHASH_ELT_TAG(pageidx);
/*
* now search the bucket for the requested tag
*/
LIST_FOREACH(elt, swhash, list) {
if (elt->tag == page_tag) {
return elt;
}
}
if (!create) {
return NULL;
}
/*
* allocate a new entry for the bucket and init/insert it in
*/
elt = pool_get(&uao_swhash_elt_pool, PR_NOWAIT);
if (elt == NULL) {
return NULL;
}
LIST_INSERT_HEAD(swhash, elt, list);
elt->tag = page_tag;
elt->count = 0;
memset(elt->slots, 0, sizeof(elt->slots));
return elt;
}
/*
* uao_find_swslot: find the swap slot number for an aobj/pageidx
*
* => object must be locked by caller
*/
int
uao_find_swslot(struct uvm_object *uobj, int pageidx)
{
struct uvm_aobj *aobj = (struct uvm_aobj *)uobj;
struct uao_swhash_elt *elt;
KASSERT(UVM_OBJ_IS_AOBJ(uobj));
/*
* if noswap flag is set, then we never return a slot
*/
if (aobj->u_flags & UAO_FLAG_NOSWAP)
return 0;
/*
* if hashing, look in hash table.
*/
if (UAO_USES_SWHASH(aobj)) {
elt = uao_find_swhash_elt(aobj, pageidx, false);
return elt ? UAO_SWHASH_ELT_PAGESLOT(elt, pageidx) : 0;
}
/*
* otherwise, look in the array
*/
return aobj->u_swslots[pageidx];
}
/*
* uao_set_swslot: set the swap slot for a page in an aobj.
*
* => setting a slot to zero frees the slot
* => object must be locked by caller
* => we return the old slot number, or -1 if we failed to allocate
* memory to record the new slot number
*/
int
uao_set_swslot(struct uvm_object *uobj, int pageidx, int slot)
{
struct uvm_aobj *aobj = (struct uvm_aobj *)uobj;
struct uao_swhash_elt *elt;
int oldslot;
UVMHIST_FUNC(__func__);
UVMHIST_CALLARGS(pdhist, "aobj %#jx pageidx %jd slot %jd",
(uintptr_t)aobj, pageidx, slot, 0);
KASSERT(rw_write_held(uobj->vmobjlock) || uobj->uo_refs == 0);
KASSERT(UVM_OBJ_IS_AOBJ(uobj));
/*
* if noswap flag is set, then we can't set a non-zero slot.
*/
if (aobj->u_flags & UAO_FLAG_NOSWAP) {
KASSERTMSG(slot == 0, "uao_set_swslot: no swap object");
return 0;
}
/*
* are we using a hash table? if so, add it in the hash.
*/
if (UAO_USES_SWHASH(aobj)) {
/*
* Avoid allocating an entry just to free it again if
* the page had not swap slot in the first place, and
* we are freeing.
*/
elt = uao_find_swhash_elt(aobj, pageidx, slot != 0);
if (elt == NULL) {
return slot ? -1 : 0;
}
oldslot = UAO_SWHASH_ELT_PAGESLOT(elt, pageidx);
UAO_SWHASH_ELT_PAGESLOT(elt, pageidx) = slot;
/*
* now adjust the elt's reference counter and free it if we've
* dropped it to zero.
*/
if (slot) {
if (oldslot == 0)
elt->count++;
} else {
if (oldslot)
elt->count--;
if (elt->count == 0) {
LIST_REMOVE(elt, list);
pool_put(&uao_swhash_elt_pool, elt);
}
}
} else {
/* we are using an array */
oldslot = aobj->u_swslots[pageidx];
aobj->u_swslots[pageidx] = slot;
}
return oldslot;
}
#endif /* defined(VMSWAP) */
/*
* end of hash/array functions
*/
/*
* uao_free: free all resources held by an aobj, and then free the aobj
*
* => the aobj should be dead
*/
static void
uao_free(struct uvm_aobj *aobj)
{
struct uvm_object *uobj = &aobj->u_obj;
KASSERT(UVM_OBJ_IS_AOBJ(uobj));
KASSERT(rw_write_held(uobj->vmobjlock));
uao_dropswap_range(uobj, 0, 0);
rw_exit(uobj->vmobjlock);
#if defined(VMSWAP)
if (UAO_USES_SWHASH(aobj)) {
/*
* free the hash table itself.
*/
hashdone(aobj->u_swhash, HASH_LIST, aobj->u_swhashmask);
} else {
/*
* free the array itself.
*/
kmem_free(aobj->u_swslots, aobj->u_pages * sizeof(int));
}
#endif /* defined(VMSWAP) */
/*
* finally free the aobj itself
*/
uvm_obj_destroy(uobj, true);
kmem_free(aobj, sizeof(struct uvm_aobj));
}
/*
* pager functions
*/
/*
* uao_create: create an aobj of the given size and return its uvm_object.
*
* => for normal use, flags are always zero
* => for the kernel object, the flags are:
* UAO_FLAG_KERNOBJ - allocate the kernel object (can only happen once)
* UAO_FLAG_KERNSWAP - enable swapping of kernel object (" ")
*/
struct uvm_object *
uao_create(voff_t size, int flags)
{
static struct uvm_aobj kernel_object_store;
static krwlock_t bootstrap_kernel_object_lock;
static int kobj_alloced __diagused = 0;
pgoff_t pages = round_page((uint64_t)size) >> PAGE_SHIFT;
struct uvm_aobj *aobj;
int refs;
/*
* Allocate a new aobj, unless kernel object is requested.
*/
if (flags & UAO_FLAG_KERNOBJ) {
KASSERT(!kobj_alloced);
aobj = &kernel_object_store;
aobj->u_pages = pages;
aobj->u_flags = UAO_FLAG_NOSWAP;
refs = UVM_OBJ_KERN;
kobj_alloced = UAO_FLAG_KERNOBJ;
} else if (flags & UAO_FLAG_KERNSWAP) {
KASSERT(kobj_alloced == UAO_FLAG_KERNOBJ);
aobj = &kernel_object_store;
kobj_alloced = UAO_FLAG_KERNSWAP;
refs = 0xdeadbeaf; /* XXX: gcc */
} else {
aobj = kmem_alloc(sizeof(struct uvm_aobj), KM_SLEEP);
aobj->u_pages = pages;
aobj->u_flags = 0;
refs = 1;
}
/*
* no freelist by default
*/
aobj->u_freelist = VM_NFREELIST;
/*
* allocate hash/array if necessary
*
* note: in the KERNSWAP case no need to worry about locking since
* we are still booting we should be the only thread around.
*/
const int kernswap = (flags & UAO_FLAG_KERNSWAP) != 0;
if (flags == 0 || kernswap) {
#if defined(VMSWAP)
/* allocate hash table or array depending on object size */
if (UAO_USES_SWHASH(aobj)) {
aobj->u_swhash = hashinit(UAO_SWHASH_BUCKETS(aobj),
HASH_LIST, true, &aobj->u_swhashmask);
} else {
aobj->u_swslots = kmem_zalloc(pages * sizeof(int),
KM_SLEEP);
}
#endif /* defined(VMSWAP) */
/*
* Replace kernel_object's temporary static lock with
* a regular rw_obj. We cannot use uvm_obj_setlock()
* because that would try to free the old lock.
*/
if (kernswap) {
aobj->u_obj.vmobjlock = rw_obj_alloc();
rw_destroy(&bootstrap_kernel_object_lock);
}
if (flags) {
aobj->u_flags &= ~UAO_FLAG_NOSWAP; /* clear noswap */
return &aobj->u_obj;
}
}
/*
* Initialise UVM object.
*/
const bool kernobj = (flags & UAO_FLAG_KERNOBJ) != 0;
uvm_obj_init(&aobj->u_obj, &aobj_pager, !kernobj, refs);
if (__predict_false(kernobj)) {
/* Use a temporary static lock for kernel_object. */
rw_init(&bootstrap_kernel_object_lock);
uvm_obj_setlock(&aobj->u_obj, &bootstrap_kernel_object_lock);
}
/*
* now that aobj is ready, add it to the global list
*/
mutex_enter(&uao_list_lock);
LIST_INSERT_HEAD(&uao_list, aobj, u_list);
mutex_exit(&uao_list_lock);
return(&aobj->u_obj);
}
/*
* uao_set_pgfl: allocate pages only from the specified freelist.
*
* => must be called before any pages are allocated for the object.
* => reset by setting it to VM_NFREELIST, meaning any freelist.
*/
void
uao_set_pgfl(struct uvm_object *uobj, int freelist)
{
struct uvm_aobj *aobj = (struct uvm_aobj *)uobj;
KASSERTMSG((0 <= freelist), "invalid freelist %d", freelist);
KASSERTMSG((freelist <= VM_NFREELIST), "invalid freelist %d",
freelist);
aobj->u_freelist = freelist;
}
/*
* uao_pagealloc: allocate a page for aobj.
*/
static inline struct vm_page *
uao_pagealloc(struct uvm_object *uobj, voff_t offset, int flags)
{
struct uvm_aobj *aobj = (struct uvm_aobj *)uobj;
if (__predict_true(aobj->u_freelist == VM_NFREELIST))
return uvm_pagealloc(uobj, offset, NULL, flags);
else
return uvm_pagealloc_strat(uobj, offset, NULL, flags,
UVM_PGA_STRAT_ONLY, aobj->u_freelist);
}
/*
* uao_init: set up aobj pager subsystem
*
* => called at boot time from uvm_pager_init()
*/
void
uao_init(void)
{
static int uao_initialized;
if (uao_initialized)
return;
uao_initialized = true;
LIST_INIT(&uao_list);
mutex_init(&uao_list_lock, MUTEX_DEFAULT, IPL_NONE);
pool_init(&uao_swhash_elt_pool, sizeof(struct uao_swhash_elt),
0, 0, 0, "uaoeltpl", NULL, IPL_VM);
}
/*
* uao_reference: hold a reference to an anonymous UVM object.
*/
void
uao_reference(struct uvm_object *uobj)
{
/* Kernel object is persistent. */
if (UVM_OBJ_IS_KERN_OBJECT(uobj)) {
return;
}
atomic_inc_uint(&uobj->uo_refs);
}
/*
* uao_detach: drop a reference to an anonymous UVM object.
*/
void
uao_detach(struct uvm_object *uobj)
{
struct uvm_aobj *aobj = (struct uvm_aobj *)uobj;
struct uvm_page_array a;
struct vm_page *pg;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);
/*
* Detaching from kernel object is a NOP.
*/
if (UVM_OBJ_IS_KERN_OBJECT(uobj))
return;
/*
* Drop the reference. If it was the last one, destroy the object.
*/
KASSERT(uobj->uo_refs > 0);
UVMHIST_LOG(maphist," (uobj=%#jx) ref=%jd",
(uintptr_t)uobj, uobj->uo_refs, 0, 0);
membar_release();
if (atomic_dec_uint_nv(&uobj->uo_refs) > 0) {
UVMHIST_LOG(maphist, "<- done (rc>0)", 0,0,0,0);
return;
}
membar_acquire();
/*
* Remove the aobj from the global list.
*/
mutex_enter(&uao_list_lock);
LIST_REMOVE(aobj, u_list);
mutex_exit(&uao_list_lock);
/*
* Free all the pages left in the aobj. For each page, when the
* page is no longer busy (and thus after any disk I/O that it is
* involved in is complete), release any swap resources and free
* the page itself.
*/
uvm_page_array_init(&a, uobj, 0);
rw_enter(uobj->vmobjlock, RW_WRITER);
while ((pg = uvm_page_array_fill_and_peek(&a, 0, 0)) != NULL) {
uvm_page_array_advance(&a);
pmap_page_protect(pg, VM_PROT_NONE);
if (pg->flags & PG_BUSY) {
uvm_pagewait(pg, uobj->vmobjlock, "uao_det");
uvm_page_array_clear(&a);
rw_enter(uobj->vmobjlock, RW_WRITER);
continue;
}
uao_dropswap(&aobj->u_obj, pg->offset >> PAGE_SHIFT);
uvm_pagefree(pg);
}
uvm_page_array_fini(&a);
/*
* Finally, free the anonymous UVM object itself.
*/
uao_free(aobj);
}
/*
* uao_put: flush pages out of a uvm object
*
* => object should be locked by caller. we may _unlock_ the object
* if (and only if) we need to clean a page (PGO_CLEANIT).
* XXXJRT Currently, however, we don't. In the case of cleaning
* XXXJRT a page, we simply just deactivate it. Should probably
* XXXJRT handle this better, in the future (although "flushing"
* XXXJRT anonymous memory isn't terribly important).
* => if PGO_CLEANIT is not set, then we will neither unlock the object
* or block.
* => if PGO_ALLPAGE is set, then all pages in the object are valid targets
* for flushing.
* => we return 0 unless we encountered some sort of I/O error
* XXXJRT currently never happens, as we never directly initiate
* XXXJRT I/O
*/
static int
uao_put(struct uvm_object *uobj, voff_t start, voff_t stop, int flags)
{
struct uvm_aobj *aobj = (struct uvm_aobj *)uobj;
struct uvm_page_array a;
struct vm_page *pg;
voff_t curoff;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);
KASSERT(UVM_OBJ_IS_AOBJ(uobj));
KASSERT(rw_write_held(uobj->vmobjlock));
if (flags & PGO_ALLPAGES) {
start = 0;
stop = aobj->u_pages << PAGE_SHIFT;
} else {
start = trunc_page(start);
if (stop == 0) {
stop = aobj->u_pages << PAGE_SHIFT;
} else {
stop = round_page(stop);
}
if (stop > (uint64_t)(aobj->u_pages << PAGE_SHIFT)) {
printf("uao_put: strange, got an out of range "
"flush %#jx > %#jx (fixed)\n",
(uintmax_t)stop,
(uintmax_t)(aobj->u_pages << PAGE_SHIFT));
stop = aobj->u_pages << PAGE_SHIFT;
}
}
UVMHIST_LOG(maphist,
" flush start=%#jx, stop=%#jx, flags=%#jx",
start, stop, flags, 0);
/*
* Don't need to do any work here if we're not freeing
* or deactivating pages.
*/
if ((flags & (PGO_DEACTIVATE|PGO_FREE)) == 0) {
rw_exit(uobj->vmobjlock);
return 0;
}
/* locked: uobj */
uvm_page_array_init(&a, uobj, 0);
curoff = start;
while ((pg = uvm_page_array_fill_and_peek(&a, curoff, 0)) != NULL) {
if (pg->offset >= stop) {
break;
}
/*
* wait and try again if the page is busy.
*/
if (pg->flags & PG_BUSY) {
uvm_pagewait(pg, uobj->vmobjlock, "uao_put");
uvm_page_array_clear(&a);
rw_enter(uobj->vmobjlock, RW_WRITER);
continue;
}
uvm_page_array_advance(&a);
curoff = pg->offset + PAGE_SIZE;
switch (flags & (PGO_CLEANIT|PGO_FREE|PGO_DEACTIVATE)) {
/*
* XXX In these first 3 cases, we always just
* XXX deactivate the page. We may want to
* XXX handle the different cases more specifically
* XXX in the future.
*/
case PGO_CLEANIT|PGO_FREE:
case PGO_CLEANIT|PGO_DEACTIVATE:
case PGO_DEACTIVATE:
deactivate_it:
uvm_pagelock(pg);
uvm_pagedeactivate(pg);
uvm_pageunlock(pg);
break;
case PGO_FREE:
/*
* If there are multiple references to
* the object, just deactivate the page.
*/
if (uobj->uo_refs > 1)
goto deactivate_it;
/*
* free the swap slot and the page.
*/
pmap_page_protect(pg, VM_PROT_NONE);
/*
* freeing swapslot here is not strictly necessary.
* however, leaving it here doesn't save much
* because we need to update swap accounting anyway.
*/
uao_dropswap(uobj, pg->offset >> PAGE_SHIFT);
uvm_pagefree(pg);
break;
default:
panic("%s: impossible", __func__);
}
}
rw_exit(uobj->vmobjlock);
uvm_page_array_fini(&a);
return 0;
}
/*
* uao_get: fetch me a page
*
* we have three cases:
* 1: page is resident -> just return the page.
* 2: page is zero-fill -> allocate a new page and zero it.
* 3: page is swapped out -> fetch the page from swap.
*
* case 1 can be handled with PGO_LOCKED, cases 2 and 3 cannot.
* so, if the "center" page hits case 2/3 then we will need to return EBUSY.
*
* => prefer map unlocked (not required)
* => object must be locked! we will _unlock_ it before starting any I/O.
* => flags: PGO_LOCKED: fault data structures are locked
* => NOTE: offset is the offset of pps[0], _NOT_ pps[centeridx]
* => NOTE: caller must check for released pages!!
*/
static int
uao_get(struct uvm_object *uobj, voff_t offset, struct vm_page **pps,
int *npagesp, int centeridx, vm_prot_t access_type, int advice, int flags)
{
voff_t current_offset;
struct vm_page *ptmp;
int lcv, gotpages, maxpages, swslot, pageidx;
bool overwrite = ((flags & PGO_OVERWRITE) != 0);
struct uvm_page_array a;
UVMHIST_FUNC(__func__);
UVMHIST_CALLARGS(pdhist, "aobj=%#jx offset=%jd, flags=%#jx",
(uintptr_t)uobj, offset, flags,0);
/*
* the object must be locked. it can only be a read lock when
* processing a read fault with PGO_LOCKED.
*/
KASSERT(UVM_OBJ_IS_AOBJ(uobj));
KASSERT(rw_lock_held(uobj->vmobjlock));
KASSERT(rw_write_held(uobj->vmobjlock) ||
((flags & PGO_LOCKED) != 0 && (access_type & VM_PROT_WRITE) == 0));
/*
* get number of pages
*/
maxpages = *npagesp;
/*
* step 1: handled the case where fault data structures are locked.
*/
if (flags & PGO_LOCKED) {
/*
* step 1a: get pages that are already resident. only do
* this if the data structures are locked (i.e. the first
* time through).
*/
uvm_page_array_init(&a, uobj, 0);
gotpages = 0; /* # of pages we got so far */
for (lcv = 0; lcv < maxpages; lcv++) {
ptmp = uvm_page_array_fill_and_peek(&a,
offset + (lcv << PAGE_SHIFT), maxpages);
if (ptmp == NULL) {
break;
}
KASSERT(ptmp->offset >= offset);
lcv = (ptmp->offset - offset) >> PAGE_SHIFT;
if (lcv >= maxpages) {
break;
}
uvm_page_array_advance(&a);
/*
* to be useful must get a non-busy page
*/
if ((ptmp->flags & PG_BUSY) != 0) {
continue;
}
/*
* useful page: plug it in our result array
*/
KASSERT(uvm_pagegetdirty(ptmp) !=
UVM_PAGE_STATUS_CLEAN);
pps[lcv] = ptmp;
gotpages++;
}
uvm_page_array_fini(&a);
/*
* step 1b: now we've either done everything needed or we
* to unlock and do some waiting or I/O.
*/
UVMHIST_LOG(pdhist, "<- done (done=%jd)",
(pps[centeridx] != NULL), 0,0,0);
*npagesp = gotpages;
return pps[centeridx] != NULL ? 0 : EBUSY;
}
/*
* step 2: get non-resident or busy pages.
* object is locked. data structures are unlocked.
*/
if ((flags & PGO_SYNCIO) == 0) {
goto done;
}
uvm_page_array_init(&a, uobj, 0);
for (lcv = 0, current_offset = offset ; lcv < maxpages ;) {
/*
* we have yet to locate the current page (pps[lcv]). we
* first look for a page that is already at the current offset.
* if we find a page, we check to see if it is busy or
* released. if that is the case, then we sleep on the page
* until it is no longer busy or released and repeat the lookup.
* if the page we found is neither busy nor released, then we
* busy it (so we own it) and plug it into pps[lcv]. we are
* ready to move on to the next page.
*/
ptmp = uvm_page_array_fill_and_peek(&a, current_offset,
maxpages - lcv);
if (ptmp != NULL && ptmp->offset == current_offset) {
/* page is there, see if we need to wait on it */
if ((ptmp->flags & PG_BUSY) != 0) {
UVMHIST_LOG(pdhist,
"sleeping, ptmp->flags %#jx\n",
ptmp->flags,0,0,0);
uvm_pagewait(ptmp, uobj->vmobjlock, "uao_get");
rw_enter(uobj->vmobjlock, RW_WRITER);
uvm_page_array_clear(&a);
continue;
}
/*
* if we get here then the page is resident and
* unbusy. we busy it now (so we own it). if
* overwriting, mark the page dirty up front as
* it will be zapped via an unmanaged mapping.
*/
KASSERT(uvm_pagegetdirty(ptmp) !=
UVM_PAGE_STATUS_CLEAN);
if (overwrite) {
uvm_pagemarkdirty(ptmp, UVM_PAGE_STATUS_DIRTY);
}
/* we own it, caller must un-busy */
ptmp->flags |= PG_BUSY;
UVM_PAGE_OWN(ptmp, "uao_get2");
pps[lcv++] = ptmp;
current_offset += PAGE_SIZE;
uvm_page_array_advance(&a);
continue;
} else {
KASSERT(ptmp == NULL || ptmp->offset > current_offset);
}
/*
* not resident. allocate a new busy/fake/clean page in the
* object. if it's in swap we need to do I/O to fill in the
* data, otherwise the page needs to be cleared: if it's not
* destined to be overwritten, then zero it here and now.
*/
pageidx = current_offset >> PAGE_SHIFT;
swslot = uao_find_swslot(uobj, pageidx);
ptmp = uao_pagealloc(uobj, current_offset,
swslot != 0 || overwrite ? 0 : UVM_PGA_ZERO);
/* out of RAM? */
if (ptmp == NULL) {
rw_exit(uobj->vmobjlock);
UVMHIST_LOG(pdhist, "sleeping, ptmp == NULL",0,0,0,0);
uvm_wait("uao_getpage");
rw_enter(uobj->vmobjlock, RW_WRITER);
uvm_page_array_clear(&a);
continue;
}
/*
* if swslot == 0, page hasn't existed before and is zeroed.
* otherwise we have a "fake/busy/clean" page that we just
* allocated. do the needed "i/o", reading from swap.
*/
if (swslot != 0) {
#if defined(VMSWAP)
int error;
UVMHIST_LOG(pdhist, "pagein from swslot %jd",
swslot, 0,0,0);
/*
* page in the swapped-out page.
* unlock object for i/o, relock when done.
*/
uvm_page_array_clear(&a);
rw_exit(uobj->vmobjlock);
error = uvm_swap_get(ptmp, swslot, PGO_SYNCIO);
rw_enter(uobj->vmobjlock, RW_WRITER);
/*
* I/O done. check for errors.
*/
if (error != 0) {
UVMHIST_LOG(pdhist, "<- done (error=%jd)",
error,0,0,0);
/*
* remove the swap slot from the aobj
* and mark the aobj as having no real slot.
* don't free the swap slot, thus preventing
* it from being used again.
*/
swslot = uao_set_swslot(uobj, pageidx,
SWSLOT_BAD);
if (swslot > 0) {
uvm_swap_markbad(swslot, 1);
}
uvm_pagefree(ptmp);
rw_exit(uobj->vmobjlock);
UVMHIST_LOG(pdhist, "<- done (error)",
error,lcv,0,0);
if (lcv != 0) {
uvm_page_unbusy(pps, lcv);
}
memset(pps, 0, maxpages * sizeof(pps[0]));
uvm_page_array_fini(&a);
return error;
}
#else /* defined(VMSWAP) */
panic("%s: pagein", __func__);
#endif /* defined(VMSWAP) */
}
/*
* note that we will allow the page being writably-mapped
* (!PG_RDONLY) regardless of access_type. if overwrite,
* the page can be modified through an unmanaged mapping
* so mark it dirty up front.
*/
if (overwrite) {
uvm_pagemarkdirty(ptmp, UVM_PAGE_STATUS_DIRTY);
} else {
uvm_pagemarkdirty(ptmp, UVM_PAGE_STATUS_UNKNOWN);
}
/*
* we got the page! clear the fake flag (indicates valid
* data now in page) and plug into our result array. note
* that page is still busy.
*
* it is the callers job to:
* => check if the page is released
* => unbusy the page
* => activate the page
*/
KASSERT(uvm_pagegetdirty(ptmp) != UVM_PAGE_STATUS_CLEAN);
KASSERT((ptmp->flags & PG_FAKE) != 0);
KASSERT(ptmp->offset == current_offset);
ptmp->flags &= ~PG_FAKE;
pps[lcv++] = ptmp;
current_offset += PAGE_SIZE;
}
uvm_page_array_fini(&a);
/*
* finally, unlock object and return.
*/
done:
rw_exit(uobj->vmobjlock);
UVMHIST_LOG(pdhist, "<- done (OK)",0,0,0,0);
return 0;
}
#if defined(VMSWAP)
/*
* uao_dropswap: release any swap resources from this aobj page.
*
* => aobj must be locked or have a reference count of 0.
*/
void
uao_dropswap(struct uvm_object *uobj, int pageidx)
{
int slot;
KASSERT(UVM_OBJ_IS_AOBJ(uobj));
slot = uao_set_swslot(uobj, pageidx, 0);
if (slot) {
uvm_swap_free(slot, 1);
}
}
/*
* page in every page in every aobj that is paged-out to a range of swslots.
*
* => nothing should be locked.
* => returns true if pagein was aborted due to lack of memory.
*/
bool
uao_swap_off(int startslot, int endslot)
{
struct uvm_aobj *aobj;
/*
* Walk the list of all anonymous UVM objects. Grab the first.
*/
mutex_enter(&uao_list_lock);
if ((aobj = LIST_FIRST(&uao_list)) == NULL) {
mutex_exit(&uao_list_lock);
return false;
}
uao_reference(&aobj->u_obj);
do {
struct uvm_aobj *nextaobj;
bool rv;
/*
* Prefetch the next object and immediately hold a reference
* on it, so neither the current nor the next entry could
* disappear while we are iterating.
*/
if ((nextaobj = LIST_NEXT(aobj, u_list)) != NULL) {
uao_reference(&nextaobj->u_obj);
}
mutex_exit(&uao_list_lock);
/*
* Page in all pages in the swap slot range.
*/
rw_enter(aobj->u_obj.vmobjlock, RW_WRITER);
rv = uao_pagein(aobj, startslot, endslot);
rw_exit(aobj->u_obj.vmobjlock);
/* Drop the reference of the current object. */
uao_detach(&aobj->u_obj);
if (rv) {
if (nextaobj) {
uao_detach(&nextaobj->u_obj);
}
return rv;
}
aobj = nextaobj;
mutex_enter(&uao_list_lock);
} while (aobj);
mutex_exit(&uao_list_lock);
return false;
}
/*
* page in any pages from aobj in the given range.
*
* => aobj must be locked and is returned locked.
* => returns true if pagein was aborted due to lack of memory.
*/
static bool
uao_pagein(struct uvm_aobj *aobj, int startslot, int endslot)
{
bool rv;
if (UAO_USES_SWHASH(aobj)) {
struct uao_swhash_elt *elt;
int buck;
restart:
for (buck = aobj->u_swhashmask; buck >= 0; buck--) {
for (elt = LIST_FIRST(&aobj->u_swhash[buck]);
elt != NULL;
elt = LIST_NEXT(elt, list)) {
int i;
for (i = 0; i < UAO_SWHASH_CLUSTER_SIZE; i++) {
int slot = elt->slots[i];
/*
* if the slot isn't in range, skip it.
*/
if (slot < startslot ||
slot >= endslot) {
continue;
}
/*
* process the page,
* the start over on this object
* since the swhash elt
* may have been freed.
*/
rv = uao_pagein_page(aobj,
UAO_SWHASH_ELT_PAGEIDX_BASE(elt) + i);
if (rv) {
return rv;
}
goto restart;
}
}
}
} else {
int i;
for (i = 0; i < aobj->u_pages; i++) {
int slot = aobj->u_swslots[i];
/*
* if the slot isn't in range, skip it
*/
if (slot < startslot || slot >= endslot) {
continue;
}
/*
* process the page.
*/
rv = uao_pagein_page(aobj, i);
if (rv) {
return rv;
}
}
}
return false;
}
/*
* uao_pagein_page: page in a single page from an anonymous UVM object.
*
* => Returns true if pagein was aborted due to lack of memory.
* => Object must be locked and is returned locked.
*/
static bool
uao_pagein_page(struct uvm_aobj *aobj, int pageidx)
{
struct uvm_object *uobj = &aobj->u_obj;
struct vm_page *pg;
int rv, npages;
pg = NULL;
npages = 1;
KASSERT(rw_write_held(uobj->vmobjlock));
rv = uao_get(uobj, (voff_t)pageidx << PAGE_SHIFT, &pg, &npages,
0, VM_PROT_READ | VM_PROT_WRITE, 0, PGO_SYNCIO);
/*
* relock and finish up.
*/
rw_enter(uobj->vmobjlock, RW_WRITER);
switch (rv) {
case 0:
break;
case EIO:
case ERESTART:
/*
* nothing more to do on errors.
* ERESTART can only mean that the anon was freed,
* so again there's nothing to do.
*/
return false;
default:
return true;
}
/*
* ok, we've got the page now.
* mark it as dirty, clear its swslot and un-busy it.
*/
uao_dropswap(&aobj->u_obj, pageidx);
/*
* make sure it's on a page queue.
*/
uvm_pagelock(pg);
uvm_pageenqueue(pg);
uvm_pagewakeup(pg);
uvm_pageunlock(pg);
pg->flags &= ~(PG_BUSY|PG_FAKE);
uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY);
UVM_PAGE_OWN(pg, NULL);
return false;
}
/*
* uao_dropswap_range: drop swapslots in the range.
*
* => aobj must be locked and is returned locked.
* => start is inclusive. end is exclusive.
*/
void
uao_dropswap_range(struct uvm_object *uobj, voff_t start, voff_t end)
{
struct uvm_aobj *aobj = (struct uvm_aobj *)uobj;
int swpgonlydelta = 0;
KASSERT(UVM_OBJ_IS_AOBJ(uobj));
KASSERT(rw_write_held(uobj->vmobjlock));
if (end == 0) {
end = INT64_MAX;
}
if (UAO_USES_SWHASH(aobj)) {
int i, hashbuckets = aobj->u_swhashmask + 1;
voff_t taghi;
voff_t taglo;
taglo = UAO_SWHASH_ELT_TAG(start);
taghi = UAO_SWHASH_ELT_TAG(end);
for (i = 0; i < hashbuckets; i++) {
struct uao_swhash_elt *elt, *next;
for (elt = LIST_FIRST(&aobj->u_swhash[i]);
elt != NULL;
elt = next) {
int startidx, endidx;
int j;
next = LIST_NEXT(elt, list);
if (elt->tag < taglo || taghi < elt->tag) {
continue;
}
if (elt->tag == taglo) {
startidx =
UAO_SWHASH_ELT_PAGESLOT_IDX(start);
} else {
startidx = 0;
}
if (elt->tag == taghi) {
endidx =
UAO_SWHASH_ELT_PAGESLOT_IDX(end);
} else {
endidx = UAO_SWHASH_CLUSTER_SIZE;
}
for (j = startidx; j < endidx; j++) {
int slot = elt->slots[j];
KASSERT(uvm_pagelookup(&aobj->u_obj,
(UAO_SWHASH_ELT_PAGEIDX_BASE(elt)
+ j) << PAGE_SHIFT) == NULL);
if (slot > 0) {
uvm_swap_free(slot, 1);
swpgonlydelta++;
KASSERT(elt->count > 0);
elt->slots[j] = 0;
elt->count--;
}
}
if (elt->count == 0) {
LIST_REMOVE(elt, list);
pool_put(&uao_swhash_elt_pool, elt);
}
}
}
} else {
int i;
if (aobj->u_pages < end) {
end = aobj->u_pages;
}
for (i = start; i < end; i++) {
int slot = aobj->u_swslots[i];
if (slot > 0) {
uvm_swap_free(slot, 1);
swpgonlydelta++;
}
}
}
/*
* adjust the counter of pages only in swap for all
* the swap slots we've freed.
*/
if (swpgonlydelta > 0) {
KASSERT(uvmexp.swpgonly >= swpgonlydelta);
atomic_add_int(&uvmexp.swpgonly, -swpgonlydelta);
}
}
#endif /* defined(VMSWAP) */