Move the NFS FHA (File Handle Affinity) code from sys/nfsserver to

sys/nfs, since it is now shared by the two NFS servers.

Suggested by:	rmacklem
Sponsored by:	Spectra Logic
MFC after:	2 weeks

2 files changed, 668 insertions, 0 deletions

diff --git a/sys/nfs/nfs_fha.c b/sys/nfs/nfs_fha.c
new file mode 100644
index 0000000..dd9ee27
--- /dev/null
+++ b/sys/nfs/nfs_fha.c
@@ -0,0 +1,556 @@
+/*-
+ * 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("$FreeBSD$");
+
+#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 <nfs/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];
+
+	/*
+	 * A small hash table to map filehandles to fha_hash_entry
+	 * structures.
+	 */
+	softc->g_fha.hashtable = hashinit(256, M_NFS_FHA,
+	    &softc->g_fha.hashmask);
+
+	/*
+	 * 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)
+{
+	sysctl_ctx_free(&softc->sysctl_ctx);
+	hashdestroy(softc->g_fha.hashtable, M_NFS_FHA, softc->g_fha.hashmask);
+}
+
+/*
+ * 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;
+	fhandle_t fh;
+	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(&fh, v3, &md, &dpos);
+	if (error)
+		goto out;
+
+	bcopy(fh.fh_fid.fid_data, &i->fh, sizeof(i->fh));
+
+	/* 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)
+{
+
+	if (e->num_rw + e->num_exclusive)
+		panic("nonempty fhe");
+	free(e, M_NFS_FHA);
+}
+
+static void
+fha_hash_entry_remove(struct fha_hash_entry *e)
+{
+
+	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;
+
+	pool = *softc->pool;
+
+	struct fha_hash_entry *fhe, *new_fhe;
+
+	LIST_FOREACH(fhe, &softc->g_fha.hashtable[fh % softc->g_fha.hashmask],
+	    link)
+		if (fhe->fh == fh)
+			break;
+
+	if (!fhe) {
+		/* Allocate a new entry. */
+		mtx_unlock(&pool->sp_lock);
+		new_fhe = fha_hash_entry_new(fh);
+		mtx_lock(&pool->sp_lock);
+
+		/* Double-check to make sure we still need the new entry. */
+		LIST_FOREACH(fhe,
+		    &softc->g_fha.hashtable[fh % softc->g_fha.hashmask], link)
+			if (fhe->fh == fh)
+				break;
+		if (!fhe) {
+			fhe = new_fhe;
+			LIST_INSERT_HEAD(
+			    &softc->g_fha.hashtable[fh % softc->g_fha.hashmask],
+			    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)
+{
+
+	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)
+{
+
+	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)
+{
+
+	if (LK_EXCLUSIVE == locktype)
+		fhe->num_exclusive += count;
+	else
+		fhe->num_rw += count;
+}
+
+static SVCTHREAD *
+get_idle_thread(SVCPOOL *pool)
+{
+	SVCTHREAD *st;
+
+	LIST_FOREACH(st, &pool->sp_idlethreads, st_ilink) {
+		if (st->st_xprt == NULL && STAILQ_EMPTY(&st->st_reqs))
+			return (st);
+	}
+	return (NULL);
+}
+
+
+/*
+ * Get the service thread currently associated with the fhe that is
+ * appropriate to handle this operation.
+ */
+SVCTHREAD *
+fha_hash_entry_choose_thread(struct fha_params *softc,
+    struct fha_hash_entry *fhe, struct fha_info *i, SVCTHREAD *this_thread);
+
+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_reqcount;
+
+		/* 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 = STAILQ_FIRST(&thread->st_reqs)->rq_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)) {
+		/*
+		 * We can add a new thread, so try for an idle thread
+		 * first, and fall back to this_thread if none are idle.
+		 */
+		if (STAILQ_EMPTY(&this_thread->st_reqs)) {
+			thread = this_thread;
+#if 0
+			ITRACE_CURPROC(ITRACE_NFS, ITRACE_INFO,
+			    "fha: %p(%d)t", thread, thread->st_reqcount);
+#endif
+		} else if ((thread = get_idle_thread(pool))) {
+#if 0
+			ITRACE_CURPROC(ITRACE_NFS, ITRACE_INFO,
+			    "fha: %p(%d)i", thread, thread->st_reqcount);
+#endif
+		} else {
+			thread = this_thread;
+#if 0
+			ITRACE_CURPROC(ITRACE_NFS, ITRACE_INFO,
+			    "fha: %p(%d)b", thread, thread->st_reqcount);
+#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)
+{
+	SVCPOOL *pool;
+	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)
+		return (this_thread);
+
+	/*
+	 * Only do placement if this is an NFS request.
+	 */
+	if (req->rq_prog != NFS_PROG)
+		return (this_thread);
+
+	if (req->rq_vers != 2 && req->rq_vers != 3)
+		return (this_thread);
+
+	pool = req->rq_xprt->xp_pool;
+	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);
+
+	return (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;
+
+	/*
+	 * 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;
+
+	fha_hash_entry_add_op(fhe, req->rq_p2, -1);
+
+	if (thread->st_reqcount == 0) {
+		fha_hash_entry_remove_thread(fhe, thread);
+		if (0 == fhe->num_rw + fhe->num_exclusive)
+			fha_hash_entry_remove(fhe);
+	}
+}
+
+int
+fhe_stats_sysctl(SYSCTL_HANDLER_ARGS, struct fha_params *softc)
+{
+	int error, count, i;
+	struct sbuf sb;
+	struct fha_hash_entry *fhe;
+	bool_t first = TRUE;
+	SVCTHREAD *thread;
+	SVCPOOL *pool;
+
+	sbuf_new(&sb, NULL, 4096, SBUF_FIXEDLEN);
+
+	pool = NULL;
+
+	if (!*softc->pool) {
+		sbuf_printf(&sb, "NFSD not running\n");
+		goto out;
+	}
+	pool = *softc->pool;
+
+	mtx_lock(&pool->sp_lock);
+	count = 0;
+	for (i = 0; i <= softc->g_fha.hashmask; i++)
+		if (!LIST_EMPTY(&softc->g_fha.hashtable[i]))
+			count++;
+
+	if (count == 0) {
+		sbuf_printf(&sb, "No file handle entries.\n");
+		goto out;
+	}
+
+	for (i = 0; i <= softc->g_fha.hashmask; i++) {
+		LIST_FOREACH(fhe, &softc->g_fha.hashtable[i], link) {
+			sbuf_printf(&sb, "%sfhe %p: {\n", first ? "" : ", ", fhe);
+
+			sbuf_printf(&sb, "    fh: %ju\n", (uintmax_t) fhe->fh);
+			sbuf_printf(&sb, "    num_rw: %d\n", fhe->num_rw);
+			sbuf_printf(&sb, "    num_exclusive: %d\n", 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 "
+				    "(count %d)\n", thread,
+				    STAILQ_FIRST(&thread->st_reqs)->rq_p3,
+				    thread->st_reqcount);
+			}
+
+			sbuf_printf(&sb, "}");
+			first = FALSE;
+
+			/* Limit the output. */
+			if (++count > 128) {
+				sbuf_printf(&sb, "...");
+				break;
+			}
+		}
+	}
+
+ out:
+	if (pool)
+		mtx_unlock(&pool->sp_lock);
+	sbuf_trim(&sb);
+	sbuf_finish(&sb);
+	error = sysctl_handle_string(oidp, sbuf_data(&sb), sbuf_len(&sb), req);
+	sbuf_delete(&sb);
+	return (error);
+}
diff --git a/sys/nfs/nfs_fha.h b/sys/nfs/nfs_fha.h
new file mode 100644
index 0000000..ef5ada0
--- /dev/null
+++ b/sys/nfs/nfs_fha.h
@@ -0,0 +1,112 @@
+/*-
+ * 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.
+ */
+/* $FreeBSD$ */
+
+#ifndef	_NFS_FHA_H
+#define	_NFS_FHA_H 1
+
+#ifdef	_KERNEL
+
+/* Sysctl defaults. */
+#define FHA_DEF_ENABLE			1
+#define FHA_DEF_BIN_SHIFT		22 /* 4MB */
+#define FHA_DEF_MAX_NFSDS_PER_FH	8
+#define FHA_DEF_MAX_REQS_PER_NFSD	0  /* Unlimited */
+
+/* This is the global structure that represents the state of the fha system. */
+struct fha_global {
+	struct fha_hash_entry_list *hashtable;
+	u_long hashmask;
+};
+
+struct fha_ctls {
+	int	 enable;
+	uint32_t bin_shift;
+	uint32_t max_nfsds_per_fh;
+	uint32_t max_reqs_per_nfsd;
+};
+
+/*
+ * These are the entries in the filehandle hash.  They talk about a specific
+ * file, requests against which are being handled by one or more nfsds.  We
+ * keep a chain of nfsds against the file. We only have more than one if reads
+ * are ongoing, and then only if the reads affect disparate regions of the
+ * file.
+ *
+ * In general, we want to assign a new request to an existing nfsd if it is
+ * going to contend with work happening already on that nfsd, or if the
+ * operation is a read and the nfsd is already handling a proximate read.  We
+ * do this to avoid jumping around in the read stream unnecessarily, and to
+ * avoid contention between threads over single files.
+ */
+struct fha_hash_entry {
+	LIST_ENTRY(fha_hash_entry) link;
+	u_int64_t fh;
+	u_int32_t num_rw;
+	u_int32_t num_exclusive;
+	u_int8_t num_threads;
+	struct svcthread_list threads;
+};
+
+LIST_HEAD(fha_hash_entry_list, fha_hash_entry);
+
+/* A structure used for passing around data internally. */
+struct fha_info {
+	u_int64_t fh;
+	off_t offset;
+	int locktype;
+};
+
+struct fha_callbacks {
+	rpcproc_t (*get_procnum)(rpcproc_t procnum);
+	int (*realign)(struct mbuf **mb, int malloc_flags);
+	int (*get_fh)(fhandle_t *fh, int v3, struct mbuf **md, caddr_t *dpos);
+	int (*is_read)(rpcproc_t procnum);
+	int (*is_write)(rpcproc_t procnum);
+	int (*get_offset)(struct mbuf **md, caddr_t *dpos, int v3, struct
+			  fha_info *info);
+	int (*no_offset)(rpcproc_t procnum);
+	void (*set_locktype)(rpcproc_t procnum, struct fha_info *info);
+	int (*fhe_stats_sysctl)(SYSCTL_HANDLER_ARGS);
+};
+
+struct fha_params {
+	struct fha_global g_fha; 
+	struct sysctl_ctx_list sysctl_ctx;
+	struct sysctl_oid *sysctl_tree;
+	struct fha_ctls ctls;
+	struct fha_callbacks callbacks;
+	char server_name[32];
+	SVCPOOL **pool;
+};
+
+void fha_nd_complete(SVCTHREAD *, struct svc_req *);
+SVCTHREAD *fha_assign(SVCTHREAD *, struct svc_req *, struct fha_params *);
+void fha_init(struct fha_params *softc);
+void fha_uninit(struct fha_params *softc);
+int fhe_stats_sysctl(SYSCTL_HANDLER_ARGS, struct fha_params *softc);
+
+#endif /* _KERNEL */
+#endif /* _NFS_FHA_H_ */