/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright 2024 Oxide Computer Company
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/kmem.h>
#include <sys/vnode.h>
#include <sys/vfs_opreg.h>
#include <sys/swap.h>
#include <sys/sysmacros.h>
#include <sys/buf.h>
#include <sys/callb.h>
#include <sys/debug.h>
#include <vm/seg.h>
#include <sys/fs/swapnode.h>
#include <fs/fs_subr.h>
#include <sys/cmn_err.h>
#include <sys/mem_config.h>
#include <sys/atomic.h>

extern const fs_operation_def_t swap_vnodeops_template[];

/*
 * swapfs_minfree is the amount of physical memory (actually remaining
 * availrmem) that we want to keep free for the rest of the system.  This
 * means that swapfs can only grow to availrmem - swapfs_minfree.  This
 * can be set as just constant value or a certain percentage of installed
 * physical memory. It is set in swapinit().
 *
 * Users who want to change the amount of memory that can be used as swap
 * space should do so by setting swapfs_desfree at boot time,
 * not swapfs_minfree.
 */

pgcnt_t swapfs_desfree = 0;
pgcnt_t swapfs_minfree = 0;
pgcnt_t swapfs_reserve = 0;

#ifdef SWAPFS_DEBUG
int swapfs_debug;
#endif /* SWAPFS_DEBUG */


static int swapfs_vpcount;
static kmutex_t swapfs_lock;
static struct async_reqs *sw_ar, *sw_pendlist, *sw_freelist;

static struct vnode **swap_vnodes;      /* ptr's to swap vnodes */

static void swap_init_mem_config(void);

static pgcnt_t initial_swapfs_desfree;
static pgcnt_t initial_swapfs_minfree;
static pgcnt_t initial_swapfs_reserve;

static int swap_sync(struct vfs *vfsp, short flag, struct cred *cr);

static void
swapfs_recalc_save_initial(void)
{
        initial_swapfs_desfree = swapfs_desfree;
        initial_swapfs_minfree = swapfs_minfree;
        initial_swapfs_reserve = swapfs_reserve;
}

static int
swapfs_recalc(pgcnt_t pgs)
{
        pgcnt_t new_swapfs_desfree;
        pgcnt_t new_swapfs_minfree;
        pgcnt_t new_swapfs_reserve;

        new_swapfs_desfree = initial_swapfs_desfree;
        new_swapfs_minfree = initial_swapfs_minfree;
        new_swapfs_reserve = initial_swapfs_reserve;

        if (new_swapfs_desfree == 0)
                new_swapfs_desfree = btopr(7 * 512 * 1024); /* 3-1/2Mb */;

        if (new_swapfs_minfree == 0) {
                /*
                 * Set swapfs_minfree to be an eighth of physical, but
                 * capped at 512 MiB.
                 */
                new_swapfs_minfree = MIN(btopr(512 * 1024 * 1024), pgs >> 3);
        }

        /*
         * priv processes can reserve memory as swap as long as availrmem
         * remains greater than swapfs_minfree; in the case of non-priv
         * processes, memory can be reserved as swap only if availrmem
         * doesn't fall below (swapfs_minfree + swapfs_reserve). Thus,
         * swapfs_reserve amount of memswap is not available to non-priv
         * processes. This protects daemons such as automounter dying
         * as a result of application processes eating away almost entire
         * membased swap. This safeguard becomes useless if apps are run
         * with root access.
         *
         * set swapfs_reserve to a minimum of 4Mb or 1/128 of physmem whichever
         * is greater up to the limit of 128 MB.
         */
        if (new_swapfs_reserve == 0)
                new_swapfs_reserve = MIN(btopr(128 * 1024 * 1024),
                    MAX(btopr(4 * 1024 * 1024), pgs >> 7));

        /* Test basic numeric viability. */
        if (new_swapfs_minfree > pgs)
                return (0);

        /* Equivalent test to anon_resvmem() check. */
        if (availrmem < new_swapfs_minfree) {
                /*
                 * If ism pages are being used, then there must be agreement
                 * between these two policies.
                 */
                if ((availrmem > segspt_minfree) && (segspt_minfree > 0)) {
                        new_swapfs_minfree = segspt_minfree;
                } else {
                        return (0);
                }
        }

        swapfs_desfree = new_swapfs_desfree;
        swapfs_minfree = new_swapfs_minfree;
        swapfs_reserve = new_swapfs_reserve;

        return (1);
}

/*ARGSUSED1*/
int
swapinit(int fstype, char *name)
{
        /* reserve for mp */
        ssize_t sw_freelist_size = klustsize / PAGESIZE * 2;
        int i, error;

        static const fs_operation_def_t swap_vfsops[] = {
                VFSNAME_SYNC, { .vfs_sync = swap_sync },
                NULL, NULL
        };

        SWAPFS_PRINT(SWAP_SUBR, "swapinit\n", 0, 0, 0, 0, 0);
        mutex_init(&swapfs_lock, NULL, MUTEX_DEFAULT, NULL);

        swap_vnodes = kmem_zalloc(MAX_SWAP_VNODES * sizeof (struct vnode *),
            KM_SLEEP);

        swapfs_recalc_save_initial();
        if (!swapfs_recalc(physmem))
                cmn_err(CE_PANIC, "swapfs_minfree(%lu) > physmem(%lu)",
                    swapfs_minfree, physmem);

        /*
         * Arrange for a callback on memory size change.
         */
        swap_init_mem_config();

        sw_ar = (struct async_reqs *)
            kmem_zalloc(sw_freelist_size*sizeof (struct async_reqs), KM_SLEEP);

        error = vfs_setfsops(fstype, swap_vfsops, NULL);
        if (error != 0) {
                cmn_err(CE_WARN, "swapinit: bad vfs ops template");
                return (error);
        }

        error = vn_make_ops(name, swap_vnodeops_template, &swap_vnodeops);
        if (error != 0) {
                (void) vfs_freevfsops_by_type(fstype);
                cmn_err(CE_WARN, "swapinit: bad vnode ops template");
                return (error);
        }
        sw_freelist = sw_ar;
        for (i = 0; i < sw_freelist_size - 1; i++)
                sw_ar[i].a_next = &sw_ar[i + 1];

        return (0);
}

/*
 * Get a swapfs vnode corresponding to the specified identifier.
 */
struct vnode *
swapfs_getvp(ulong_t vidx)
{
        struct vnode *vp;

        vp = swap_vnodes[vidx];
        if (vp) {
                return (vp);
        }

        mutex_enter(&swapfs_lock);
        vp = swap_vnodes[vidx];
        if (vp == NULL) {
                vp = vn_alloc(KM_SLEEP);
                vn_setops(vp, swap_vnodeops);
                vp->v_type = VREG;
                vp->v_flag |= (VISSWAP|VISSWAPFS);
                swap_vnodes[vidx] = vp;
                swapfs_vpcount++;
        }
        mutex_exit(&swapfs_lock);
        return (vp);
}

int swap_lo;

/*ARGSUSED*/
static int
swap_sync(struct vfs *vfsp, short flag, struct cred *cr)
{
        struct vnode *vp;
        int i;

        if (!(flag & SYNC_ALL))
                return (1);

        /*
         * assumes that we are the only one left to access this so that
         * no need to use swapfs_lock (since it's staticly defined)
         */
        for (i = 0; i < MAX_SWAP_VNODES; i++) {
                vp = swap_vnodes[i];
                if (vp) {
                        VN_HOLD(vp);
                        (void) VOP_PUTPAGE(vp, (offset_t)0, 0,
                            (B_ASYNC | B_FREE), kcred, NULL);
                        VN_RELE(vp);
                }
        }
        return (0);
}

extern int sw_pending_size;

/*
 * Take an async request off the pending queue
 */
struct async_reqs *
sw_getreq()
{
        struct async_reqs *arg;

        mutex_enter(&swapfs_lock);
        arg = sw_pendlist;
        if (arg) {
                sw_pendlist = arg->a_next;
                arg->a_next = NULL;
                sw_pending_size -= PAGESIZE;
        }
        ASSERT(sw_pending_size >= 0);
        mutex_exit(&swapfs_lock);
        return (arg);
}

/*
 * Put an async request on the pending queue
 */
void
sw_putreq(struct async_reqs *arg)
{
        /* Hold onto it */
        VN_HOLD(arg->a_vp);

        mutex_enter(&swapfs_lock);
        arg->a_next = sw_pendlist;
        sw_pendlist = arg;
        sw_pending_size += PAGESIZE;
        mutex_exit(&swapfs_lock);
}

/*
 * Put an async request back on the pending queue
 */
void
sw_putbackreq(struct async_reqs *arg)
{
        mutex_enter(&swapfs_lock);
        arg->a_next = sw_pendlist;
        sw_pendlist = arg;
        sw_pending_size += PAGESIZE;
        mutex_exit(&swapfs_lock);
}

/*
 * Take an async request structure off the free list
 */
struct async_reqs *
sw_getfree()
{
        struct async_reqs *arg;

        mutex_enter(&swapfs_lock);
        arg = sw_freelist;
        if (arg) {
                sw_freelist = arg->a_next;
                arg->a_next = NULL;
        }
        mutex_exit(&swapfs_lock);
        return (arg);
}

/*
 * Put an async request structure on the free list
 */
void
sw_putfree(struct async_reqs *arg)
{
        /* Release our hold - should have locked the page by now */
        VN_RELE(arg->a_vp);

        mutex_enter(&swapfs_lock);
        arg->a_next = sw_freelist;
        sw_freelist = arg;
        mutex_exit(&swapfs_lock);
}

static pgcnt_t swapfs_pending_delete;

/*ARGSUSED*/
static void
swap_mem_config_post_add(
        void *arg,
        pgcnt_t delta_swaps)
{
        (void) swapfs_recalc(physmem - swapfs_pending_delete);
}

/*ARGSUSED*/
static int
swap_mem_config_pre_del(
        void *arg,
        pgcnt_t delta_swaps)
{
        pgcnt_t nv;

        nv = atomic_add_long_nv(&swapfs_pending_delete, (spgcnt_t)delta_swaps);
        if (!swapfs_recalc(physmem - nv)) {
                /*
                 * Tidy-up is done by the call to post_del which
                 * is always made.
                 */
                cmn_err(CE_NOTE, "Memory operation refused to ensure system "
                    "doesn't deadlock due to excessive consumption by swapfs.");
                return (EBUSY);
        }
        return (0);
}

/*ARGSUSED*/
static void
swap_mem_config_post_del(
        void *arg,
        pgcnt_t delta_swaps,
        int cancelled)
{
        pgcnt_t nv;

        nv = atomic_add_long_nv(&swapfs_pending_delete, -(spgcnt_t)delta_swaps);
        (void) swapfs_recalc(physmem - nv);
}

static kphysm_setup_vector_t swap_mem_config_vec = {
        KPHYSM_SETUP_VECTOR_VERSION,
        swap_mem_config_post_add,
        swap_mem_config_pre_del,
        swap_mem_config_post_del,
};

static void
swap_init_mem_config(void)
{
        int ret;

        ret = kphysm_setup_func_register(&swap_mem_config_vec, (void *)NULL);
        ASSERT(ret == 0);
}