/*      $OpenBSD: uvm_anon.c,v 1.67 2026/02/11 22:34:40 deraadt Exp $   */
/*      $NetBSD: uvm_anon.c,v 1.10 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.
 *
 * 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_anon.c: uvm anon ops
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/pool.h>
#include <sys/kernel.h>
#include <sys/atomic.h>

#include <uvm/uvm.h>
#include <uvm/uvm_swap.h>

struct pool uvm_anon_pool;

void
uvm_anon_init(void)
{
        pool_init(&uvm_anon_pool, sizeof(struct vm_anon), 0, IPL_MPFLOOR,
            PR_WAITOK, "anonpl", NULL);
        pool_sethiwat(&uvm_anon_pool, atomic_load_sint(&uvmexp.free) / 16);
}

void
uvm_anon_init_percpu(void)
{
#ifdef MULTIPROCESSOR
        pool_cache_init(&uvm_anon_pool);
#endif
}

/*
 * uvm_analloc: allocate a new anon.
 *
 * => anon will have no lock associated.
 */
struct vm_anon *
uvm_analloc(void)
{
        struct vm_anon *anon;

        anon = pool_get(&uvm_anon_pool, PR_NOWAIT);
        if (anon) {
                anon->an_lock = NULL;
                anon->an_ref = 1;
                anon->an_page = NULL;
                anon->an_swslot = 0;
        }
        return anon;
}

/*
 * uvm_anfree: free a single anon structure
 *
 * => anon must be removed from the amap (if anon was in an amap).
 * => amap must be locked, if anon was owned by amap.
 */
void
uvm_anfree(struct vm_anon *anon)
{
        struct vm_page *pg = anon->an_page;

        KASSERT(anon->an_lock == NULL || rw_write_held(anon->an_lock));
        KASSERT(anon->an_ref == 0);

        /*
         * Dispose of the page, if it is resident.
         */
        if (pg != NULL) {
                KASSERT(anon->an_lock != NULL);

                /*
                 * If the page is busy, mark it as PG_RELEASED, so
                 * that uvm_anon_release(9) would release it later.
                 */
                if ((pg->pg_flags & PG_BUSY) != 0) {
                        atomic_setbits_int(&pg->pg_flags, PG_RELEASED);
                        rw_obj_hold(anon->an_lock);
                        return;
                }
                pmap_page_protect(pg, PROT_NONE);
                uvm_pagefree(pg);
        } else {
                if (anon->an_swslot != 0 && anon->an_swslot != SWSLOT_BAD) {
                        /* This page is no longer only in swap. */
                        KASSERT(atomic_load_sint(&uvmexp.swpgonly) > 0);
                        atomic_dec_int(&uvmexp.swpgonly);
                }
        }
        anon->an_lock = NULL;

        /*
         * Free any swap resources, leave a page replacement hint.
         */
        uvm_anon_dropswap(anon);

        KASSERT(anon->an_page == NULL);
        KASSERT(anon->an_swslot == 0);

        pool_put(&uvm_anon_pool, anon);
}

/*
 * uvm_anwait: wait for memory to become available to allocate an anon.
 */
void
uvm_anwait(void)
{
        struct vm_anon *anon;

        /* XXX: Want something like pool_wait()? */
        anon = pool_get(&uvm_anon_pool, PR_WAITOK);
        pool_put(&uvm_anon_pool, anon);
}

/*
 * uvm_anon_pagein: fetch an anon's page.
 *
 * => anon must be locked, and is unlocked upon return.
 * => returns true if pagein was aborted due to lack of memory.
 */

boolean_t
uvm_anon_pagein(struct vm_amap *amap, struct vm_anon *anon)
{
        struct vm_page *pg;
        int rv;

        KASSERT(rw_write_held(anon->an_lock));
        KASSERT(anon->an_lock == amap->am_lock);

        /*
         * Get the page of the anon.
         */
        rv = uvmfault_anonget(NULL, amap, anon);

        switch (rv) {
        case 0:
                /* Success - we have the page. */
                KASSERT(rw_write_held(anon->an_lock));
                break;
        case EACCES:
        case ERESTART:
                /*
                 * Nothing more to do on errors.  ERESTART means that the
                 * anon was freed.
                 */
                return FALSE;
        case ENOLCK:
                /* Should not be possible. */
        default:
#ifdef DIAGNOSTIC
                panic("anon_pagein: uvmfault_anonget -> %d", rv);
#else
                return FALSE;
#endif
        }

        /*
         * Mark the page as dirty and clear its swslot.
         */
        pg = anon->an_page;
        if (anon->an_swslot > 0) {
                uvm_swap_free(anon->an_swslot, 1);
        }
        anon->an_swslot = 0;
        atomic_clearbits_int(&pg->pg_flags, PG_CLEAN);

        /*
         * Deactivate the page (to put it on a page queue).
         */
        uvm_pagedeactivate(pg);
        rw_exit(anon->an_lock);

        return FALSE;
}

/*
 * uvm_anon_dropswap: release any swap resources from this anon.
 *
 * => anon must be locked or have a reference count of 0.
 */
void
uvm_anon_dropswap(struct vm_anon *anon)
{
        KASSERT(anon->an_ref == 0 || rw_lock_held(anon->an_lock));

        if (anon->an_swslot == 0)
                return;

        uvm_swap_free(anon->an_swslot, 1);
        anon->an_swslot = 0;
}


/*
 * uvm_anon_release: release an anon and its page.
 *
 * => anon should not have any references.
 * => anon must be locked.
 */

void
uvm_anon_release(struct vm_anon *anon)
{
        struct vm_page *pg = anon->an_page;
        struct rwlock *lock;

        KASSERT(rw_write_held(anon->an_lock));
        KASSERT(pg != NULL);
        KASSERT((pg->pg_flags & PG_RELEASED) != 0);
        KASSERT((pg->pg_flags & PG_BUSY) != 0);
        KASSERT(pg->uobject == NULL);
        KASSERT(pg->uanon == anon);
        KASSERT(anon->an_ref == 0);

        pmap_page_protect(pg, PROT_NONE);
        uvm_pagefree(pg);
        KASSERT(anon->an_page == NULL);
        lock = anon->an_lock;
        uvm_anon_dropswap(anon);
        pool_put(&uvm_anon_pool, anon);
        rw_exit(lock);
        /* Note: extra reference is held for PG_RELEASED case. */
        rw_obj_free(lock);
}