/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Rick Macklem at The University of Guelph.
 *
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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 nfs_syscalls.c     8.5 (Berkeley) 3/30/95
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/file.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/namei.h>
#include <sys/unistd.h>
#include <sys/kthread.h>
#include <sys/fcntl.h>
#include <sys/lockf.h>
#include <sys/mutex.h>
#include <sys/taskqueue.h>

#include <netinet/in.h>
#include <netinet/tcp.h>

#include <fs/nfs/nfsport.h>
#include <fs/nfsclient/nfsmount.h>
#include <fs/nfsclient/nfs.h>
#include <fs/nfsclient/nfsnode.h>

extern struct mtx       ncl_iod_mutex;
extern struct task      ncl_nfsiodnew_task;

int ncl_numasync;
enum nfsiod_state ncl_iodwant[NFS_MAXASYNCDAEMON];
struct nfsmount *ncl_iodmount[NFS_MAXASYNCDAEMON];

static void     nfssvc_iod(void *);

static int nfs_asyncdaemon[NFS_MAXASYNCDAEMON];

SYSCTL_DECL(_vfs_nfs);

/* Maximum number of seconds a nfsiod kthread will sleep before exiting */
static unsigned int nfs_iodmaxidle = 120;
SYSCTL_UINT(_vfs_nfs, OID_AUTO, iodmaxidle, CTLFLAG_RW, &nfs_iodmaxidle, 0,
    "Max number of seconds an nfsiod kthread will sleep before exiting");

/* Maximum number of nfsiod kthreads */
unsigned int ncl_iodmax = 20;

/* Minimum number of nfsiod kthreads to keep as spares */
static unsigned int nfs_iodmin = 0;

static int nfs_nfsiodnew_sync(void);

static int
sysctl_iodmin(SYSCTL_HANDLER_ARGS)
{
        int error, i;
        int newmin;

        newmin = nfs_iodmin;
        error = sysctl_handle_int(oidp, &newmin, 0, req);
        if (error || (req->newptr == NULL))
                return (error);
        NFSLOCKIOD();
        if (newmin > ncl_iodmax) {
                error = EINVAL;
                goto out;
        }
        nfs_iodmin = newmin;
        if (ncl_numasync >= nfs_iodmin)
                goto out;
        /*
         * If the current number of nfsiod is lower
         * than the new minimum, create some more.
         */
        for (i = nfs_iodmin - ncl_numasync; i > 0; i--)
                nfs_nfsiodnew_sync();
out:
        NFSUNLOCKIOD(); 
        return (0);
}
SYSCTL_PROC(_vfs_nfs, OID_AUTO, iodmin,
    CTLTYPE_UINT | CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE,
    0, sizeof (nfs_iodmin), sysctl_iodmin, "IU",
    "Min number of nfsiod kthreads to keep as spares");

static int
sysctl_iodmax(SYSCTL_HANDLER_ARGS)
{
        int error, i;
        int iod, newmax;

        newmax = ncl_iodmax;
        error = sysctl_handle_int(oidp, &newmax, 0, req);
        if (error || (req->newptr == NULL))
                return (error);
        if (newmax > NFS_MAXASYNCDAEMON)
                return (EINVAL);
        NFSLOCKIOD();
        ncl_iodmax = newmax;
        if (ncl_numasync <= ncl_iodmax)
                goto out;
        /*
         * If there are some asleep nfsiods that should
         * exit, wakeup() them so that they check ncl_iodmax
         * and exit.  Those who are active will exit as
         * soon as they finish I/O.
         */
        iod = ncl_numasync - 1;
        for (i = 0; i < ncl_numasync - ncl_iodmax; i++) {
                if (ncl_iodwant[iod] == NFSIOD_AVAILABLE)
                        wakeup(&ncl_iodwant[iod]);
                iod--;
        }
out:
        NFSUNLOCKIOD();
        return (0);
}
SYSCTL_PROC(_vfs_nfs, OID_AUTO, iodmax,
    CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof (ncl_iodmax),
    sysctl_iodmax, "IU",
    "Max number of nfsiod kthreads");

static int
nfs_nfsiodnew_sync(void)
{
        int error, i;

        NFSASSERTIOD();
        for (i = 0; i < ncl_iodmax; i++) {
                if (nfs_asyncdaemon[i] == 0) {
                        nfs_asyncdaemon[i] = 1;
                        break;
                }
        }
        if (i == ncl_iodmax)
                return (0);
        NFSUNLOCKIOD();
        error = kproc_create(nfssvc_iod, nfs_asyncdaemon + i, NULL,
            RFHIGHPID, 0, "newnfs %d", i);
        NFSLOCKIOD();
        if (error == 0) {
                ncl_numasync++;
                ncl_iodwant[i] = NFSIOD_AVAILABLE;
        } else
                nfs_asyncdaemon[i] = 0;
        return (error);
}

void
ncl_nfsiodnew_tq(__unused void *arg, int pending)
{

        NFSLOCKIOD();
        while (pending > 0) {
                pending--;
                nfs_nfsiodnew_sync();
        }
        NFSUNLOCKIOD();
}

void
ncl_nfsiodnew(void)
{

        NFSASSERTIOD();
        taskqueue_enqueue(taskqueue_thread, &ncl_nfsiodnew_task);
}

static void
nfsiod_setup(void *dummy)
{
        int error;

        TUNABLE_INT_FETCH("vfs.nfs.iodmin", &nfs_iodmin);
        nfscl_init();
        NFSLOCKIOD();
        /* Silently limit the start number of nfsiod's */
        if (nfs_iodmin > NFS_MAXASYNCDAEMON)
                nfs_iodmin = NFS_MAXASYNCDAEMON;

        while (ncl_numasync < nfs_iodmin) {
                error = nfs_nfsiodnew_sync();
                if (error == -1)
                        panic("nfsiod_setup: nfs_nfsiodnew failed");
        }
        NFSUNLOCKIOD();
}
SYSINIT(newnfsiod, SI_SUB_KTHREAD_IDLE, SI_ORDER_ANY, nfsiod_setup, NULL);

static int nfs_defect = 0;
SYSCTL_INT(_vfs_nfs, OID_AUTO, defect, CTLFLAG_RW, &nfs_defect, 0,
    "Allow nfsiods to migrate serving different mounts");

/*
 * Asynchronous I/O daemons for client nfs.
 * They do read-ahead and write-behind operations on the block I/O cache.
 * Returns if we hit the timeout defined by the iodmaxidle sysctl.
 */
static void
nfssvc_iod(void *instance)
{
        struct buf *bp;
        struct nfsmount *nmp;
        int myiod, timo;
        int error = 0;

        NFSLOCKIOD();
        myiod = (int *)instance - nfs_asyncdaemon;
        /*
         * Main loop
         */
        for (;;) {
            while (((nmp = ncl_iodmount[myiod]) == NULL)
                   || !TAILQ_FIRST(&nmp->nm_bufq)) {
                if (myiod >= ncl_iodmax)
                        goto finish;
                if (nmp)
                        nmp->nm_bufqiods--;
                if (ncl_iodwant[myiod] == NFSIOD_NOT_AVAILABLE)
                        ncl_iodwant[myiod] = NFSIOD_AVAILABLE;
                ncl_iodmount[myiod] = NULL;
                /*
                 * Always keep at least nfs_iodmin kthreads.
                 */
                timo = (myiod < nfs_iodmin) ? 0 : nfs_iodmaxidle * hz;
                error = msleep(&ncl_iodwant[myiod], &ncl_iod_mutex, PWAIT | PCATCH,
                    "-", timo);
                if (error) {
                        nmp = ncl_iodmount[myiod];
                        /*
                         * Rechecking the nm_bufq closes a rare race where the 
                         * nfsiod is woken up at the exact time the idle timeout
                         * fires
                         */
                        if (nmp && TAILQ_FIRST(&nmp->nm_bufq))
                                error = 0;
                        break;
                }
            }
            if (error)
                    break;
            while ((bp = TAILQ_FIRST(&nmp->nm_bufq)) != NULL) {
                /* Take one off the front of the list */
                TAILQ_REMOVE(&nmp->nm_bufq, bp, b_freelist);
                nmp->nm_bufqlen--;
                if (nmp->nm_bufqwant && nmp->nm_bufqlen <= ncl_numasync) {
                    nmp->nm_bufqwant = 0;
                    wakeup(&nmp->nm_bufq);
                }
                NFSUNLOCKIOD();
                KASSERT((bp->b_flags & B_DIRECT) == 0,
                    ("nfssvc_iod: B_DIRECT set"));
                if (bp->b_iocmd == BIO_READ)
                        (void) ncl_doio(bp->b_vp, bp, bp->b_rcred,
                            NULL, 0);
                else
                        (void) ncl_doio(bp->b_vp, bp, bp->b_wcred,
                            NULL, 0);
                NFSLOCKIOD();
                /*
                 * Make sure the nmp hasn't been dismounted as soon as
                 * ncl_doio() completes for the last buffer.
                 */
                nmp = ncl_iodmount[myiod];
                if (nmp == NULL)
                        break;

                /*
                 * If there are more than one iod on this mount, then defect
                 * so that the iods can be shared out fairly between the mounts
                 */
                if (nfs_defect && nmp->nm_bufqiods > 1) {
                    NFS_DPF(ASYNCIO,
                            ("nfssvc_iod: iod %d defecting from mount %p\n",
                             myiod, nmp));
                    ncl_iodmount[myiod] = NULL;
                    nmp->nm_bufqiods--;
                    break;
                }
            }
        }
finish:
        nfs_asyncdaemon[myiod] = 0;
        if (nmp)
            nmp->nm_bufqiods--;
        ncl_iodwant[myiod] = NFSIOD_NOT_AVAILABLE;
        ncl_iodmount[myiod] = NULL;
        /* Someone may be waiting for the last nfsiod to terminate. */
        if (--ncl_numasync == 0)
                wakeup(&ncl_numasync);
        NFSUNLOCKIOD();
        if ((error == 0) || (error == EWOULDBLOCK))
                kproc_exit(0);
        /* Abnormal termination */
        kproc_exit(1);
}