/*      $NetBSD: nfs_fha.c,v 1.2 2016/12/13 22:41:46 pgoyette Exp $     */
/*-
 * Copyright (c) 2008 Isilon Inc http://www.isilon.com/
 *
 * 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 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 AUTHOR 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.
 */

#include <sys/cdefs.h>
/* __FBSDID("FreeBSD: head/sys/nfs/nfs_fha.c 267479 2014-06-14 12:26:12Z mav "); */
__RCSID("$NetBSD: nfs_fha.c,v 1.2 2016/12/13 22:41:46 pgoyette Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mbuf.h>
#include <sys/sbuf.h>

#include <rpc/rpc.h>
#include <fs/nfs/common/nfs_fha.h>

static MALLOC_DEFINE(M_NFS_FHA, "NFS FHA", "NFS FHA");

/*
 * XXX need to commonize definitions between old and new NFS code.  Define
 * this here so we don't include one nfsproto.h over the other.
 */
#define NFS_PROG                100003

void
fha_init(struct fha_params *softc)
{
        char tmpstr[128];
        int i;

        for (i = 0; i < FHA_HASH_SIZE; i++)
                mtx_init(&softc->fha_hash[i].mtx, "fhalock", NULL, MTX_DEF);

        /*
         * Set the default tuning parameters.
         */
        softc->ctls.enable = FHA_DEF_ENABLE;
        softc->ctls.bin_shift = FHA_DEF_BIN_SHIFT;
        softc->ctls.max_nfsds_per_fh = FHA_DEF_MAX_NFSDS_PER_FH;
        softc->ctls.max_reqs_per_nfsd = FHA_DEF_MAX_REQS_PER_NFSD;

        /*
         * Allow the user to override the defaults at boot time with
         * tunables.
         */
        snprintf(tmpstr, sizeof(tmpstr), "vfs.%s.fha.enable",
            softc->server_name);
        TUNABLE_INT_FETCH(tmpstr, &softc->ctls.enable);
        snprintf(tmpstr, sizeof(tmpstr), "vfs.%s.fha.bin_shift",
            softc->server_name);
        TUNABLE_INT_FETCH(tmpstr, &softc->ctls.bin_shift);
        snprintf(tmpstr, sizeof(tmpstr), "vfs.%s.fha.max_nfsds_per_fh",
            softc->server_name);
        TUNABLE_INT_FETCH(tmpstr, &softc->ctls.max_nfsds_per_fh);
        snprintf(tmpstr, sizeof(tmpstr), "vfs.%s.fha.max_reqs_per_nfsd",
            softc->server_name);
        TUNABLE_INT_FETCH(tmpstr, &softc->ctls.max_reqs_per_nfsd);

        /*
         * Add sysctls so the user can change the tuning parameters at
         * runtime.
         */
        SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
            OID_AUTO, "enable", CTLFLAG_RW,
            &softc->ctls.enable, 0, "Enable NFS File Handle Affinity (FHA)");

        SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
            OID_AUTO, "bin_shift", CTLFLAG_RW,
            &softc->ctls.bin_shift, 0, "For FHA reads, no two requests will "
            "contend if they're 2^(bin_shift) bytes apart");

        SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
            OID_AUTO, "max_nfsds_per_fh", CTLFLAG_RW,
            &softc->ctls.max_nfsds_per_fh, 0, "Maximum nfsd threads that "
            "should be working on requests for the same file handle");

        SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
            OID_AUTO, "max_reqs_per_nfsd", CTLFLAG_RW,
            &softc->ctls.max_reqs_per_nfsd, 0, "Maximum requests that "
            "single nfsd thread should be working on at any time");

        SYSCTL_ADD_OID(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
            OID_AUTO, "fhe_stats", CTLTYPE_STRING | CTLFLAG_RD, 0, 0,
            softc->callbacks.fhe_stats_sysctl, "A", "");

}

void
fha_uninit(struct fha_params *softc)
{
        int i;

        sysctl_ctx_free(&softc->sysctl_ctx);
        for (i = 0; i < FHA_HASH_SIZE; i++)
                mtx_destroy(&softc->fha_hash[i].mtx);
}

/*
 * This just specifies that offsets should obey affinity when within
 * the same 1Mbyte (1<<20) chunk for the file (reads only for now).
 */
static void
fha_extract_info(struct svc_req *req, struct fha_info *i,
    struct fha_callbacks *cb)
{
        struct mbuf *md;
        caddr_t dpos;
        static u_int64_t random_fh = 0;
        int error;
        int v3 = (req->rq_vers == 3);
        rpcproc_t procnum;

        /*
         * We start off with a random fh.  If we get a reasonable
         * procnum, we set the fh.  If there's a concept of offset
         * that we're interested in, we set that.
         */
        i->fh = ++random_fh;
        i->offset = 0;
        i->locktype = LK_EXCLUSIVE;

        /*
         * Extract the procnum and convert to v3 form if necessary,
         * taking care to deal with out-of-range procnums.  Caller will
         * ensure that rq_vers is either 2 or 3.
         */
        procnum = req->rq_proc;
        if (!v3) {
                rpcproc_t tmp_procnum;

                tmp_procnum = cb->get_procnum(procnum);
                if (tmp_procnum == -1)
                        goto out;
                procnum = tmp_procnum;
        }

        /*
         * We do affinity for most.  However, we divide a realm of affinity
         * by file offset so as to allow for concurrent random access.  We
         * only do this for reads today, but this may change when IFS supports
         * efficient concurrent writes.
         */
        if (cb->no_offset(procnum))
                goto out;

        error = cb->realign(&req->rq_args, M_NOWAIT);
        if (error)
                goto out;
        md = req->rq_args;
        dpos = mtod(md, caddr_t);

        /* Grab the filehandle. */
        error = cb->get_fh(&i->fh, v3, &md, &dpos);
        if (error)
                goto out;

        /* Content ourselves with zero offset for all but reads. */
        if (cb->is_read(procnum) || cb->is_write(procnum))
                cb->get_offset(&md, &dpos, v3, i);

out:
        cb->set_locktype(procnum, i);
}

static struct fha_hash_entry *
fha_hash_entry_new(u_int64_t fh)
{
        struct fha_hash_entry *e;

        e = malloc(sizeof(*e), M_NFS_FHA, M_WAITOK);
        e->fh = fh;
        e->num_rw = 0;
        e->num_exclusive = 0;
        e->num_threads = 0;
        LIST_INIT(&e->threads);

        return (e);
}

static void
fha_hash_entry_destroy(struct fha_hash_entry *e)
{

        mtx_assert(e->mtx, MA_OWNED);
        KASSERT(e->num_rw == 0,
            ("%d reqs on destroyed fhe %p", e->num_rw, e));
        KASSERT(e->num_exclusive == 0,
            ("%d exclusive reqs on destroyed fhe %p", e->num_exclusive, e));
        KASSERT(e->num_threads == 0,
            ("%d threads on destroyed fhe %p", e->num_threads, e));
        free(e, M_NFS_FHA);
}

static void
fha_hash_entry_remove(struct fha_hash_entry *e)
{

        mtx_assert(e->mtx, MA_OWNED);
        LIST_REMOVE(e, link);
        fha_hash_entry_destroy(e);
}

static struct fha_hash_entry *
fha_hash_entry_lookup(struct fha_params *softc, u_int64_t fh)
{
        SVCPOOL *pool;
        struct fha_hash_slot *fhs;
        struct fha_hash_entry *fhe, *new_fhe;

        pool = *softc->pool;
        fhs = &softc->fha_hash[fh % FHA_HASH_SIZE];
        new_fhe = fha_hash_entry_new(fh);
        new_fhe->mtx = &fhs->mtx;
        mtx_lock(&fhs->mtx);
        LIST_FOREACH(fhe, &fhs->list, link)
                if (fhe->fh == fh)
                        break;
        if (!fhe) {
                fhe = new_fhe;
                LIST_INSERT_HEAD(&fhs->list, fhe, link);
        } else
                fha_hash_entry_destroy(new_fhe);
        return (fhe);
}

static void
fha_hash_entry_add_thread(struct fha_hash_entry *fhe, SVCTHREAD *thread)
{

        mtx_assert(fhe->mtx, MA_OWNED);
        thread->st_p2 = 0;
        LIST_INSERT_HEAD(&fhe->threads, thread, st_alink);
        fhe->num_threads++;
}

static void
fha_hash_entry_remove_thread(struct fha_hash_entry *fhe, SVCTHREAD *thread)
{

        mtx_assert(fhe->mtx, MA_OWNED);
        KASSERT(thread->st_p2 == 0,
            ("%d reqs on removed thread %p", thread->st_p2, thread));
        LIST_REMOVE(thread, st_alink);
        fhe->num_threads--;
}

/*
 * Account for an ongoing operation associated with this file.
 */
static void
fha_hash_entry_add_op(struct fha_hash_entry *fhe, int locktype, int count)
{

        mtx_assert(fhe->mtx, MA_OWNED);
        if (LK_EXCLUSIVE == locktype)
                fhe->num_exclusive += count;
        else
                fhe->num_rw += count;
}

/*
 * Get the service thread currently associated with the fhe that is
 * appropriate to handle this operation.
 */
static SVCTHREAD *
fha_hash_entry_choose_thread(struct fha_params *softc,
    struct fha_hash_entry *fhe, struct fha_info *i, SVCTHREAD *this_thread)
{
        SVCTHREAD *thread, *min_thread = NULL;
        SVCPOOL *pool;
        int req_count, min_count = 0;
        off_t offset1, offset2;

        pool = *softc->pool;

        LIST_FOREACH(thread, &fhe->threads, st_alink) {
                req_count = thread->st_p2;

                /* If there are any writes in progress, use the first thread. */
                if (fhe->num_exclusive) {
#if 0
                        ITRACE_CURPROC(ITRACE_NFS, ITRACE_INFO,
                            "fha: %p(%d)w", thread, req_count);
#endif
                        return (thread);
                }

                /*
                 * Check for read locality, making sure that we won't
                 * exceed our per-thread load limit in the process.
                 */
                offset1 = i->offset;
                offset2 = thread->st_p3;

                if (((offset1 >= offset2)
                  && ((offset1 - offset2) < (1 << softc->ctls.bin_shift)))
                 || ((offset2 > offset1)
                  && ((offset2 - offset1) < (1 << softc->ctls.bin_shift)))) {
                        if ((softc->ctls.max_reqs_per_nfsd == 0) ||
                            (req_count < softc->ctls.max_reqs_per_nfsd)) {
#if 0
                                ITRACE_CURPROC(ITRACE_NFS, ITRACE_INFO,
                                    "fha: %p(%d)r", thread, req_count);
#endif
                                return (thread);
                        }
                }

                /*
                 * We don't have a locality match, so skip this thread,
                 * but keep track of the most attractive thread in case
                 * we need to come back to it later.
                 */
#if 0
                ITRACE_CURPROC(ITRACE_NFS, ITRACE_INFO,
                    "fha: %p(%d)s off1 %llu off2 %llu", thread,
                    req_count, offset1, offset2);
#endif
                if ((min_thread == NULL) || (req_count < min_count)) {
                        min_count = req_count;
                        min_thread = thread;
                }
        }

        /*
         * We didn't find a good match yet.  See if we can add
         * a new thread to this file handle entry's thread list.
         */
        if ((softc->ctls.max_nfsds_per_fh == 0) ||
            (fhe->num_threads < softc->ctls.max_nfsds_per_fh)) {
                thread = this_thread;
#if 0
                ITRACE_CURPROC(ITRACE_NFS, ITRACE_INFO,
                    "fha: %p(%d)t", thread, thread->st_p2);
#endif
                fha_hash_entry_add_thread(fhe, thread);
        } else {
                /*
                 * We don't want to use any more threads for this file, so
                 * go back to the most attractive nfsd we're already using.
                 */
                thread = min_thread;
        }

        return (thread);
}

/*
 * After getting a request, try to assign it to some thread.  Usually we
 * handle it ourselves.
 */
SVCTHREAD *
fha_assign(SVCTHREAD *this_thread, struct svc_req *req,
    struct fha_params *softc)
{
        SVCTHREAD *thread;
        struct fha_info i;
        struct fha_hash_entry *fhe;
        struct fha_callbacks *cb;

        cb = &softc->callbacks;

        /* Check to see whether we're enabled. */
        if (softc->ctls.enable == 0)
                goto thist;

        /*
         * Only do placement if this is an NFS request.
         */
        if (req->rq_prog != NFS_PROG)
                goto thist;

        if (req->rq_vers != 2 && req->rq_vers != 3)
                goto thist;

        fha_extract_info(req, &i, cb);

        /*
         * We save the offset associated with this request for later
         * nfsd matching.
         */
        fhe = fha_hash_entry_lookup(softc, i.fh);
        req->rq_p1 = fhe;
        req->rq_p2 = i.locktype;
        req->rq_p3 = i.offset;

        /*
         * Choose a thread, taking into consideration locality, thread load,
         * and the number of threads already working on this file.
         */
        thread = fha_hash_entry_choose_thread(softc, fhe, &i, this_thread);
        KASSERT(thread, ("fha_assign: NULL thread!"));
        fha_hash_entry_add_op(fhe, i.locktype, 1);
        thread->st_p2++;
        thread->st_p3 = i.offset;

        /*
         * Grab the pool lock here to not let chosen thread go away before
         * the new request inserted to its queue while we drop fhe lock.
         */
        mtx_lock(&thread->st_lock);
        mtx_unlock(fhe->mtx);

        return (thread);
thist:
        req->rq_p1 = NULL;
        mtx_lock(&this_thread->st_lock);
        return (this_thread);
}

/*
 * Called when we're done with an operation.  The request has already
 * been de-queued.
 */
void
fha_nd_complete(SVCTHREAD *thread, struct svc_req *req)
{
        struct fha_hash_entry *fhe = req->rq_p1;
        struct mtx *mtx;

        /*
         * This may be called for reqs that didn't go through
         * fha_assign (e.g. extra NULL ops used for RPCSEC_GSS.
         */
        if (!fhe)
                return;

        mtx = fhe->mtx;
        mtx_lock(mtx);
        fha_hash_entry_add_op(fhe, req->rq_p2, -1);
        thread->st_p2--;
        KASSERT(thread->st_p2 >= 0, ("Negative request count %d on %p",
            thread->st_p2, thread));
        if (thread->st_p2 == 0) {
                fha_hash_entry_remove_thread(fhe, thread);
                if (0 == fhe->num_rw + fhe->num_exclusive)
                        fha_hash_entry_remove(fhe);
        }
        mtx_unlock(mtx);
}

int
fhe_stats_sysctl(SYSCTL_HANDLER_ARGS, struct fha_params *softc)
{
        int error, i;
        struct sbuf sb;
        struct fha_hash_entry *fhe;
        bool_t first, hfirst;
        SVCTHREAD *thread;
        SVCPOOL *pool;

        sbuf_new(&sb, NULL, 65536, SBUF_FIXEDLEN);

        pool = NULL;

        if (!*softc->pool) {
                sbuf_printf(&sb, "NFSD not running\n");
                goto out;
        }
        pool = *softc->pool;

        for (i = 0; i < FHA_HASH_SIZE; i++)
                if (!LIST_EMPTY(&softc->fha_hash[i].list))
                        break;

        if (i == FHA_HASH_SIZE) {
                sbuf_printf(&sb, "No file handle entries.\n");
                goto out;
        }

        hfirst = TRUE;
        for (; i < FHA_HASH_SIZE; i++) {
                mtx_lock(&softc->fha_hash[i].mtx);
                if (LIST_EMPTY(&softc->fha_hash[i].list)) {
                        mtx_unlock(&softc->fha_hash[i].mtx);
                        continue;
                }
                sbuf_printf(&sb, "%shash %d: {\n", hfirst ? "" : ", ", i);
                first = TRUE;
                LIST_FOREACH(fhe, &softc->fha_hash[i].list, link) {
                        sbuf_printf(&sb, "%sfhe %p: {\n", first ? "  " : ", ", fhe);

                        sbuf_printf(&sb, "    fh: %ju\n", (uintmax_t) fhe->fh);
                        sbuf_printf(&sb, "    num_rw/exclusive: %d/%d\n",
                            fhe->num_rw, fhe->num_exclusive);
                        sbuf_printf(&sb, "    num_threads: %d\n", fhe->num_threads);

                        LIST_FOREACH(thread, &fhe->threads, st_alink) {
                                sbuf_printf(&sb, "      thread %p offset %ju "
                                    "reqs %d\n", thread,
                                    thread->st_p3, thread->st_p2);
                        }

                        sbuf_printf(&sb, "  }");
                        first = FALSE;
                }
                sbuf_printf(&sb, "\n}");
                mtx_unlock(&softc->fha_hash[i].mtx);
                hfirst = FALSE;
        }

 out:
        sbuf_trim(&sb);
        sbuf_finish(&sb);
        error = sysctl_handle_string(oidp, sbuf_data(&sb), sbuf_len(&sb), req);
        sbuf_delete(&sb);
        return (error);
}