xnu-1228.3.13.tar.gz

[apple/xnu.git] / bsd / nfs / nfs_lock.c

/*
 * Copyright (c) 2002-2007 Apple Inc.  All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*-
 * Copyright (c) 1997 Berkeley Software Design, Inc. 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.
 * 3. Berkeley Software Design Inc's name may not be used to endorse or
 *    promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``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 BERKELEY SOFTWARE DESIGN INC 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 BSDI nfs_lock.c,v 2.4 1998/12/14 23:49:56 jch Exp
 */

#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>         /* for hz */
#include <sys/file_internal.h>
#include <sys/malloc.h>
#include <sys/lockf.h>          /* for hz */ /* Must come after sys/malloc.h */
#include <sys/kpi_mbuf.h>
#include <sys/mount_internal.h>
#include <sys/proc_internal.h>  /* for p_start */
#include <sys/kauth.h>
#include <sys/resourcevar.h>
#include <sys/socket.h>
#include <sys/unistd.h>
#include <sys/user.h>
#include <sys/vnode_internal.h>

#include <kern/thread.h>
#include <kern/host.h>

#include <machine/limits.h>

#include <net/if.h>

#include <nfs/rpcv2.h>
#include <nfs/nfsproto.h>
#include <nfs/nfs.h>
#include <nfs/nfs_gss.h>
#include <nfs/nfsmount.h>
#include <nfs/nfsnode.h>
#include <nfs/nfs_lock.h>

#include <mach/host_priv.h>
#include <mach/mig_errors.h>
#include <mach/host_special_ports.h>
#include <lockd/lockd_mach.h>

extern void ipc_port_release_send(ipc_port_t);

#define OFF_MAX QUAD_MAX

/*
 * pending lock request messages are kept in this queue which is
 * kept sorted by transaction ID (xid).
 */
static uint64_t nfs_lockxid = 0;
static LOCKD_MSG_QUEUE nfs_pendlockq;

/*
 * This structure is used to identify processes which have acquired NFS locks.
 * Knowing which processes have ever acquired locks allows us to short-circuit
 * unlock requests for processes that have never had an NFS file lock.  Thus
 * avoiding a costly and unnecessary lockd request.
 */
struct nfs_lock_pid {
        TAILQ_ENTRY(nfs_lock_pid)       lp_lru;         /* LRU list */
        LIST_ENTRY(nfs_lock_pid)        lp_hash;        /* hash chain */
        int                             lp_valid;       /* valid entry? */
        int                             lp_time;        /* last time seen valid */
        pid_t                           lp_pid;         /* The process ID. */
        struct timeval                  lp_pid_start;   /* Start time of process id */
};

#define NFS_LOCK_PID_HASH_SIZE          64      // XXX tune me
#define NFS_LOCK_PID_HASH(pid)  \
        (&nfs_lock_pid_hash_tbl[(pid) & nfs_lock_pid_hash])
static LIST_HEAD(, nfs_lock_pid) *nfs_lock_pid_hash_tbl;
static TAILQ_HEAD(, nfs_lock_pid) nfs_lock_pid_lru;
static u_long nfs_lock_pid_hash, nfs_lock_pid_hash_trusted;

static lck_grp_t *nfs_lock_lck_grp;
static lck_mtx_t *nfs_lock_mutex;


/*
 * initialize global nfs lock state
 */
void
nfs_lockinit(void)
{
        TAILQ_INIT(&nfs_pendlockq);
        nfs_lock_pid_hash_trusted = 1;
        nfs_lock_pid_hash_tbl = hashinit(NFS_LOCK_PID_HASH_SIZE,
                                         M_TEMP, &nfs_lock_pid_hash);
        TAILQ_INIT(&nfs_lock_pid_lru);

        nfs_lock_lck_grp = lck_grp_alloc_init("nfs_lock", LCK_GRP_ATTR_NULL);
        nfs_lock_mutex = lck_mtx_alloc_init(nfs_lock_lck_grp, LCK_ATTR_NULL);
}

/*
 * change the count of NFS mounts that may need to make lockd requests
 *
 * If the mount count drops to zero, then send a shutdown request to
 * lockd if we've sent any requests to it.
 */
void
nfs_lockd_mount_change(int i)
{
        mach_port_t lockd_port = IPC_PORT_NULL;
        kern_return_t kr;
        int send_shutdown;

        lck_mtx_lock(nfs_lock_mutex);

        nfs_lockd_mounts += i;

        /* send a shutdown request if there are no more lockd mounts */
        send_shutdown = ((nfs_lockd_mounts == 0) && nfs_lockd_request_sent);
        if (send_shutdown)
                nfs_lockd_request_sent = 0;

        lck_mtx_unlock(nfs_lock_mutex);

        if (!send_shutdown)
                return;

        /*
         * Let lockd know that it is no longer need for any NFS mounts
         */
        kr = host_get_lockd_port(host_priv_self(), &lockd_port);
        if ((kr != KERN_SUCCESS) || !IPC_PORT_VALID(lockd_port)) {
                printf("nfs_lockd_mount_change: shutdown couldn't get port, kr %d, port %s\n",
                        kr, (lockd_port == IPC_PORT_NULL) ? "NULL" :
                        (lockd_port == IPC_PORT_DEAD) ? "DEAD" : "VALID");
                return;
        }

        kr = lockd_shutdown(lockd_port);
        if (kr != KERN_SUCCESS)
                printf("nfs_lockd_mount_change: shutdown %d\n", kr);

        ipc_port_release_send(lockd_port);
}

/*
 * insert a lock request message into the pending queue
 * (nfs_lock_mutex must be held)
 */
static inline void
nfs_lockdmsg_enqueue(LOCKD_MSG_REQUEST *msgreq)
{
        LOCKD_MSG_REQUEST *mr;

        mr = TAILQ_LAST(&nfs_pendlockq, nfs_lock_msg_queue);
        if (!mr || (msgreq->lmr_msg.lm_xid > mr->lmr_msg.lm_xid)) {
                /* fast path: empty queue or new largest xid */
                TAILQ_INSERT_TAIL(&nfs_pendlockq, msgreq, lmr_next);
                return;
        }
        /* slow path: need to walk list to find insertion point */
        while (mr && (msgreq->lmr_msg.lm_xid > mr->lmr_msg.lm_xid)) {
                mr = TAILQ_PREV(mr, nfs_lock_msg_queue, lmr_next);
        }
        if (mr) {
                TAILQ_INSERT_AFTER(&nfs_pendlockq, mr, msgreq, lmr_next);
        } else {
                TAILQ_INSERT_HEAD(&nfs_pendlockq, msgreq, lmr_next);
        }
}

/*
 * remove a lock request message from the pending queue
 * (nfs_lock_mutex must be held)
 */
static inline void
nfs_lockdmsg_dequeue(LOCKD_MSG_REQUEST *msgreq)
{
        TAILQ_REMOVE(&nfs_pendlockq, msgreq, lmr_next);
}

/*
 * find a pending lock request message by xid
 *
 * We search from the head of the list assuming that the message we're
 * looking for is for an older request (because we have an answer to it).
 * This assumes that lock request will be answered primarily in FIFO order.
 * However, this may not be the case if there are blocked requests.  We may
 * want to move blocked requests to a separate queue (but that'll complicate
 * duplicate xid checking).
 *
 * (nfs_lock_mutex must be held)
 */
static inline LOCKD_MSG_REQUEST *
nfs_lockdmsg_find_by_xid(uint64_t lockxid)
{
        LOCKD_MSG_REQUEST *mr;

        TAILQ_FOREACH(mr, &nfs_pendlockq, lmr_next) {
                if (mr->lmr_msg.lm_xid == lockxid)
                        return mr;
                if (mr->lmr_msg.lm_xid > lockxid)
                        return NULL;
        }
        return mr;
}

/*
 * Because we can't depend on nlm_granted messages containing the same
 * cookie we sent with the original lock request, we need code test if
 * an nlm_granted answer matches the lock request.  We also need code
 * that can find a lockd message based solely on the nlm_granted answer.
 */

/*
 * compare lockd message to answer
 *
 * returns 0 on equality and 1 if different
 */
static inline int
nfs_lockdmsg_compare_to_answer(LOCKD_MSG_REQUEST *msgreq, struct lockd_ans *ansp)
{
        if (!(ansp->la_flags & LOCKD_ANS_LOCK_INFO))
                return 1;
        if (msgreq->lmr_msg.lm_fl.l_pid != ansp->la_pid)
                return 1;
        if (msgreq->lmr_msg.lm_fl.l_start != ansp->la_start)
                return 1;
        if (msgreq->lmr_msg.lm_fl.l_len != ansp->la_len)
                return 1;
        if (msgreq->lmr_msg.lm_fh_len != ansp->la_fh_len)
                return 1;
        if (bcmp(msgreq->lmr_msg.lm_fh, ansp->la_fh, ansp->la_fh_len))
                return 1;
        return 0;
}

/*
 * find a pending lock request message based on the lock info provided
 * in the lockd_ans/nlm_granted data.  We need this because we can't
 * depend on nlm_granted messages containing the same cookie we sent
 * with the original lock request.
 *
 * We search from the head of the list assuming that the message we're
 * looking for is for an older request (because we have an answer to it).
 * This assumes that lock request will be answered primarily in FIFO order.
 * However, this may not be the case if there are blocked requests.  We may
 * want to move blocked requests to a separate queue (but that'll complicate
 * duplicate xid checking).
 *
 * (nfs_lock_mutex must be held)
 */
static inline LOCKD_MSG_REQUEST *
nfs_lockdmsg_find_by_answer(struct lockd_ans *ansp)
{
        LOCKD_MSG_REQUEST *mr;

        if (!(ansp->la_flags & LOCKD_ANS_LOCK_INFO))
                return NULL;
        TAILQ_FOREACH(mr, &nfs_pendlockq, lmr_next) {
                if (!nfs_lockdmsg_compare_to_answer(mr, ansp))
                        break;
        }
        return mr;
}

/*
 * return the next unique lock request transaction ID
 * (nfs_lock_mutex must be held)
 */
static inline uint64_t
nfs_lockxid_get(void)
{
        LOCKD_MSG_REQUEST *mr;

        /* derive initial lock xid from system time */
        if (!nfs_lockxid) {
                /*
                 * Note: it's OK if this code inits nfs_lockxid to 0 (for example,
                 * due to a broken clock) because we immediately increment it
                 * and we guarantee to never use xid 0.  So, nfs_lockxid should only
                 * ever be 0 the first time this function is called.
                 */
                struct timeval tv;
                microtime(&tv);
                nfs_lockxid = (uint64_t)tv.tv_sec << 12;
        }

        /* make sure we get a unique xid */
        do {
                /* Skip zero xid if it should ever happen.  */
                if (++nfs_lockxid == 0)
                        nfs_lockxid++;
                if (!(mr = TAILQ_LAST(&nfs_pendlockq, nfs_lock_msg_queue)) ||
                     (mr->lmr_msg.lm_xid < nfs_lockxid)) {
                        /* fast path: empty queue or new largest xid */
                        break;
                }
                /* check if xid is already in use */
        } while (nfs_lockdmsg_find_by_xid(nfs_lockxid));

        return nfs_lockxid;
}


/*
 * Check the nfs_lock_pid hash table for an entry and, if requested,
 * add the entry if it is not found.
 *
 * (Also, if adding, try to clean up some stale entries.)
 * (nfs_lock_mutex must be held)
 */
static int
nfs_lock_pid_check(proc_t p, int addflag)
{
        struct nfs_lock_pid *lp, *lplru, *lplru_next, *mlp;
        TAILQ_HEAD(, nfs_lock_pid) nfs_lock_pid_free;
        proc_t plru = PROC_NULL;
        pid_t pid;
        int error = 0;
        struct timeval now;

        TAILQ_INIT(&nfs_lock_pid_free);
        mlp = NULL;

loop:
        /* Search hash chain */
        pid = proc_pid(p);
        error = ENOENT;
        lp = NFS_LOCK_PID_HASH(pid)->lh_first;
        for (; lp != NULL; lp = lp->lp_hash.le_next)
                if (lp->lp_pid == pid) {
                        /* found pid... */
                        if (timevalcmp(&lp->lp_pid_start, &p->p_start, ==)) {
                                /* ...and it's valid */
                                /* move to tail of LRU */
                                TAILQ_REMOVE(&nfs_lock_pid_lru, lp, lp_lru);
                                microuptime(&now);
                                lp->lp_time = now.tv_sec;
                                TAILQ_INSERT_TAIL(&nfs_lock_pid_lru, lp, lp_lru);
                                error = 0;
                                break;
                        }
                        /* ...but it's no longer valid */
                        /* remove from hash, invalidate, and move to lru head */
                        LIST_REMOVE(lp, lp_hash);
                        lp->lp_valid = 0;
                        TAILQ_REMOVE(&nfs_lock_pid_lru, lp, lp_lru);
                        TAILQ_INSERT_HEAD(&nfs_lock_pid_lru, lp, lp_lru);
                        lp = NULL;
                        break;
                }

        /* if we didn't find it (valid), use any newly allocated one */
        if (!lp)
                lp = mlp;

        /* if we don't have an lp and we've been asked to add it */
        if ((error == ENOENT) && addflag && !lp) {
                /* scan lru list for invalid, stale entries to reuse/free */
                int lrucnt = 0;
                microuptime(&now);
                for (lplru = TAILQ_FIRST(&nfs_lock_pid_lru); lplru; lplru = lplru_next) {
                        lplru_next = TAILQ_NEXT(lplru, lp_lru);
                        if (lplru->lp_valid && (lplru->lp_time >= (now.tv_sec - 2))) {
                                /*
                                 * If the oldest LRU entry is relatively new, then don't
                                 * bother scanning any further.
                                 */
                                break;
                        }
                        /* remove entry from LRU, and check if it's still in use */
                        TAILQ_REMOVE(&nfs_lock_pid_lru, lplru, lp_lru);
                        if (!lplru->lp_valid || !(plru = proc_find(lplru->lp_pid)) ||
                            timevalcmp(&lplru->lp_pid_start, &plru->p_start, !=)) {
                                if (plru != PROC_NULL) {
                                        proc_rele(plru);
                                        plru = PROC_NULL;
                                }
                                /* no longer in use */
                                LIST_REMOVE(lplru, lp_hash);
                                if (!lp) {
                                        /* we'll reuse this one */
                                        lp = lplru;
                                } else {
                                        /* queue it up for freeing */
                                        TAILQ_INSERT_HEAD(&nfs_lock_pid_free, lplru, lp_lru);
                                }
                        } else {
                                /* still in use */
                                if (plru != PROC_NULL) {
                                        proc_rele(plru);
                                        plru = PROC_NULL;
                                }
                                lplru->lp_time = now.tv_sec;
                                TAILQ_INSERT_TAIL(&nfs_lock_pid_lru, lplru, lp_lru);
                        }
                        /* don't check too many entries at once */
                        if (++lrucnt > 8)
                                break;
                }
                if (!lp) {
                        /* we need to allocate a new one */
                        lck_mtx_unlock(nfs_lock_mutex);
                        MALLOC(mlp, struct nfs_lock_pid *, sizeof(struct nfs_lock_pid),
                                M_TEMP, M_WAITOK | M_ZERO);
                        lck_mtx_lock(nfs_lock_mutex);
                        if (mlp) /* make sure somebody hasn't already added this guy */
                                goto loop;
                        error = ENOMEM;
                }
        }
        if ((error == ENOENT) && addflag && lp) {
                /* (re)initialize nfs_lock_pid info */
                lp->lp_pid = pid;
                lp->lp_pid_start = p->p_start;
                /* insert pid in hash */
                LIST_INSERT_HEAD(NFS_LOCK_PID_HASH(lp->lp_pid), lp, lp_hash);
                lp->lp_valid = 1;
                lp->lp_time = now.tv_sec;
                TAILQ_INSERT_TAIL(&nfs_lock_pid_lru, lp, lp_lru);
                error = 0;
        }

        if ((mlp && (lp != mlp)) || TAILQ_FIRST(&nfs_lock_pid_free)) {
                lck_mtx_unlock(nfs_lock_mutex);
                if (mlp && (lp != mlp)) {
                        /* we didn't need this one, so we can free it */
                        FREE(mlp, M_TEMP);
                }
                /* free up any stale entries */
                while ((lp = TAILQ_FIRST(&nfs_lock_pid_free))) {
                        TAILQ_REMOVE(&nfs_lock_pid_free, lp, lp_lru);
                        FREE(lp, M_TEMP);
                }
                lck_mtx_lock(nfs_lock_mutex);
        }

        return (error);
}

#define MACH_MAX_TRIES 3

static int
send_request(LOCKD_MSG *msg, int interruptable)
{
        kern_return_t kr;
        int retries = 0;
        mach_port_t lockd_port = IPC_PORT_NULL;

        kr = host_get_lockd_port(host_priv_self(), &lockd_port);
        if (kr != KERN_SUCCESS || !IPC_PORT_VALID(lockd_port))
                return (ENOTSUP);

        do {
                /* In the kernel all mach messaging is interruptable */
                do {
                        kr = lockd_request(
                                lockd_port,
                                msg->lm_version,
                                msg->lm_flags,
                                msg->lm_xid,
                                msg->lm_fl.l_start,
                                msg->lm_fl.l_len,
                                msg->lm_fl.l_pid,
                                msg->lm_fl.l_type,
                                msg->lm_fl.l_whence,
                                (uint32_t *)&msg->lm_addr,
                                (uint32_t *)&msg->lm_cred,
                                msg->lm_fh_len,
                                msg->lm_fh);
                        if (kr != KERN_SUCCESS)
                                printf("lockd_request received %d!\n", kr);
                } while (!interruptable && kr == MACH_SEND_INTERRUPTED);
        } while (kr == MIG_SERVER_DIED && retries++ < MACH_MAX_TRIES);

        ipc_port_release_send(lockd_port);
        switch (kr) {
        case MACH_SEND_INTERRUPTED: 
                return (EINTR);
        default:
                /*
                 * Other MACH or MIG errors we will retry. Eventually
                 * we will call nfs_down and allow the user to disable 
                 * locking.
                 */
                return (EAGAIN);
        }
        return (kr);
}
                                

/*
 * NFS advisory byte-level locks (client)
 */
int
nfs3_vnop_advlock(
        struct vnop_advlock_args /* {
                struct vnodeop_desc *a_desc;
                vnode_t a_vp;
                caddr_t a_id;
                int a_op;
                struct flock *a_fl;
                int a_flags;
                vfs_context_t a_context;
        } */ *ap)
{
        vfs_context_t ctx;
        proc_t p;
        LOCKD_MSG_REQUEST msgreq;
        LOCKD_MSG *msg;
        vnode_t vp;
        nfsnode_t np;
        int error, error2;
        int interruptable;
        struct flock *fl;
        struct nfsmount *nmp;
        struct nfs_vattr nvattr;
        off_t start, end;
        struct timeval now;
        int timeo, endtime, lastmsg, wentdown = 0;
        int lockpidcheck, nfsvers;
        struct sockaddr *saddr;
        struct timespec ts;

        ctx = ap->a_context;
        p = vfs_context_proc(ctx);
        vp = ap->a_vp;
        fl = ap->a_fl;
        np = VTONFS(vp);

        nmp = VTONMP(vp);
        if (!nmp)
                return (ENXIO);
        lck_mtx_lock(&nmp->nm_lock);
        if (nmp->nm_flag & NFSMNT_NOLOCKS) {
                lck_mtx_unlock(&nmp->nm_lock);
                return (ENOTSUP);
        }
        nfsvers = nmp->nm_vers;
        lck_mtx_unlock(&nmp->nm_lock);

        /*
         * The NLM protocol doesn't allow the server to return an error
         * on ranges, so we do it.  Pre LFS (Large File Summit)
         * standards required EINVAL for the range errors.  More recent
         * standards use EOVERFLOW, but their EINVAL wording still
         * encompasses these errors.
         * Any code sensitive to this is either:
         *  1) written pre-LFS and so can handle only EINVAL, or
         *  2) written post-LFS and thus ought to be tolerant of pre-LFS
         *     implementations.
         * Since returning EOVERFLOW certainly breaks 1), we return EINVAL.
         */
        if (fl->l_whence != SEEK_END) {
                if ((fl->l_whence != SEEK_CUR && fl->l_whence != SEEK_SET) ||
                    fl->l_start < 0 ||
                    (fl->l_len > 0 && fl->l_len - 1 > OFF_MAX - fl->l_start) ||
                    (fl->l_len < 0 && fl->l_start + fl->l_len < 0))
                        return (EINVAL);
        }

        lck_mtx_lock(nfs_lock_mutex);

        /*
         * Need to check if this process has successfully acquired an NFS lock before.
         * If not, and this is an unlock request we can simply return success here.
         */
        lockpidcheck = nfs_lock_pid_check(p, 0);
        lck_mtx_unlock(nfs_lock_mutex);
        if (lockpidcheck) {
                if (lockpidcheck != ENOENT)
                        return (lockpidcheck);
                if ((ap->a_op == F_UNLCK) && nfs_lock_pid_hash_trusted)
                        return (0);
        }

        /*
         * The NFS Lock Manager protocol doesn't directly handle
         * negative lengths or SEEK_END, so we need to normalize
         * things here where we have all the info.
         * (Note: SEEK_CUR is already adjusted for at this point)
         */
        /* Convert the flock structure into a start and end. */
        switch (fl->l_whence) {
        case SEEK_SET:
        case SEEK_CUR:
                /*
                 * Caller is responsible for adding any necessary offset
                 * to fl->l_start when SEEK_CUR is used.
                 */
                start = fl->l_start;
                break;
        case SEEK_END:
                /* need to flush, and refetch attributes to make */
                /* sure we have the correct end of file offset   */
                error = nfs_lock(np, NFS_NODE_LOCK_EXCLUSIVE);
                if (error)
                        return (error);
                NATTRINVALIDATE(np);
                if (np->n_flag & NMODIFIED) {
                        nfs_unlock(np);
                        error = nfs_vinvalbuf(vp, V_SAVE, ctx, 1);
                        if (error)
                                return (error);
                } else
                        nfs_unlock(np);

                error = nfs_getattr(np, &nvattr, ctx, 0);
                nfs_data_lock(np, NFS_NODE_LOCK_SHARED);
                if (!error)
                        error = nfs_lock(np, NFS_NODE_LOCK_SHARED);
                if (error) {
                        nfs_data_unlock(np);
                        return (error);
                }
                start = np->n_size + fl->l_start;
                nfs_unlock(np);
                nfs_data_unlock(np);
                break;
        default:
                return (EINVAL);
        }
        if (fl->l_len == 0)
                end = -1;
        else if (fl->l_len > 0)
                end = start + fl->l_len - 1;
        else { /* l_len is negative */
                end = start - 1;
                start += fl->l_len;
        }
        if (start < 0)
                return (EINVAL);

        if ((nfsvers == NFS_VER2) &&
            ((start >= 0x80000000) || (end >= 0x80000000)))
                return (EINVAL);

        /*
         * Fill in the information structure.
         */
        msgreq.lmr_answered = 0;
        msgreq.lmr_errno = 0;
        msgreq.lmr_saved_errno = 0;
        msg = &msgreq.lmr_msg;
        msg->lm_version = LOCKD_MSG_VERSION;
        msg->lm_flags = 0;

        msg->lm_fl = *fl;
        msg->lm_fl.l_start = start;
        if (end != -1)
                msg->lm_fl.l_len = end - start + 1;
        msg->lm_fl.l_pid = vfs_context_pid(ctx);

        if (ap->a_flags & F_WAIT)
                msg->lm_flags |= LOCKD_MSG_BLOCK;
        if (ap->a_op == F_GETLK)
                msg->lm_flags |= LOCKD_MSG_TEST;

        nmp = VTONMP(vp);
        if (!nmp)
                return (ENXIO);

        lck_mtx_lock(&nmp->nm_lock);
        saddr = mbuf_data(nmp->nm_nam);
        bcopy(saddr, &msg->lm_addr, min(sizeof msg->lm_addr, saddr->sa_len));
        msg->lm_fh_len = (nfsvers == NFS_VER2) ? NFSX_V2FH : np->n_fhsize;
        bcopy(np->n_fhp, msg->lm_fh, msg->lm_fh_len);
        if (nfsvers == NFS_VER3)
                msg->lm_flags |= LOCKD_MSG_NFSV3;
        cru2x(vfs_context_ucred(ctx), &msg->lm_cred);

        microuptime(&now);
        lastmsg = now.tv_sec - ((nmp->nm_tprintf_delay) - (nmp->nm_tprintf_initial_delay));
        interruptable = nmp->nm_flag & NFSMNT_INT;
        lck_mtx_unlock(&nmp->nm_lock);

        lck_mtx_lock(nfs_lock_mutex);

        /* allocate unique xid */
        msg->lm_xid = nfs_lockxid_get();
        nfs_lockdmsg_enqueue(&msgreq);

        timeo = 2;

        for (;;) {
                nfs_lockd_request_sent = 1;

                /* need to drop nfs_lock_mutex while calling send_request() */
                lck_mtx_unlock(nfs_lock_mutex);
                error = send_request(msg, interruptable);
                lck_mtx_lock(nfs_lock_mutex);
                if (error && error != EAGAIN)
                        break;

                /*
                 * Always wait for an answer.  Not waiting for unlocks could
                 * cause a lock to be left if the unlock request gets dropped.
                 */

                /*
                 * Retry if it takes too long to get a response.
                 *
                 * The timeout numbers were picked out of thin air... they start
                 * at 2 and double each timeout with a max of 60 seconds.
                 *
                 * In order to maintain responsiveness, we pass a small timeout
                 * to msleep and calculate the timeouts ourselves.  This allows
                 * us to pick up on mount changes quicker.
                 */
wait_for_granted:
                error = EWOULDBLOCK;
                ts.tv_sec = 2;
                ts.tv_nsec = 0;
                microuptime(&now);
                endtime = now.tv_sec + timeo;
                while (now.tv_sec < endtime) {
                        error = error2 = 0;
                        if (!msgreq.lmr_answered)
                                error = msleep(&msgreq, nfs_lock_mutex, PCATCH | PUSER, "lockd", &ts);
                        if (msgreq.lmr_answered) {
                                /*
                                 * Note: it's possible to have a lock granted at
                                 * essentially the same time that we get interrupted.
                                 * Since the lock may be granted, we can't return an
                                 * error from this request or we might not unlock the
                                 * lock that's been granted.
                                 */
                                nmp = VTONMP(vp);
                                if ((msgreq.lmr_errno == ENOTSUP) && nmp &&
                                    (nmp->nm_state & NFSSTA_LOCKSWORK)) {
                                        /*
                                         * We have evidence that locks work, yet lockd
                                         * returned ENOTSUP.  This is probably because
                                         * it was unable to contact the server's lockd
                                         * to send it the request.
                                         *
                                         * Because we know locks work, we'll consider
                                         * this failure to be a timeout.
                                         */
                                        error = EWOULDBLOCK;
                                } else {
                                        error = 0;
                                }
                                break;
                        }
                        if (error != EWOULDBLOCK)
                                break;
                        /* check that we still have our mount... */
                        /* ...and that we still support locks */
                        nmp = VTONMP(vp);
                        if ((error2 = nfs_sigintr(nmp, NULL, vfs_context_thread(ctx), 0))) {
                                error = error2;
                                if (fl->l_type == F_UNLCK)
                                        printf("nfs_vnop_advlock: aborting unlock request, error %d\n", error);
                                break;
                        }
                        lck_mtx_lock(&nmp->nm_lock);
                        if (nmp->nm_flag & NFSMNT_NOLOCKS) {
                                lck_mtx_unlock(&nmp->nm_lock);
                                break;
                        }
                        interruptable = nmp->nm_flag & NFSMNT_INT;
                        lck_mtx_unlock(&nmp->nm_lock);
                        microuptime(&now);
                }
                if (error) {
                        /* check that we still have our mount... */
                        nmp = VTONMP(vp);
                        if ((error2 = nfs_sigintr(nmp, NULL, vfs_context_thread(ctx), 0))) {
                                error = error2;
                                if (error2 != EINTR) {
                                        if (fl->l_type == F_UNLCK)
                                                printf("nfs_vnop_advlock: aborting unlock request, error %d\n", error);
                                        break;
                                }
                        }
                        /* ...and that we still support locks */
                        lck_mtx_lock(&nmp->nm_lock);
                        if (nmp->nm_flag & NFSMNT_NOLOCKS) {
                                if (error == EWOULDBLOCK)
                                        error = ENOTSUP;
                                lck_mtx_unlock(&nmp->nm_lock);
                                break;
                        }
                        interruptable = nmp->nm_flag & NFSMNT_INT;
                        if (error != EWOULDBLOCK) {
                                lck_mtx_unlock(&nmp->nm_lock);
                                /*
                                 * We're going to bail on this request.
                                 * If we were a blocked lock request, send a cancel.
                                 */
                                if ((msgreq.lmr_errno == EINPROGRESS) &&
                                    !(msg->lm_flags & LOCKD_MSG_CANCEL)) {
                                        /* set this request up as a cancel */
                                        msg->lm_flags |= LOCKD_MSG_CANCEL;
                                        nfs_lockdmsg_dequeue(&msgreq);
                                        msg->lm_xid = nfs_lockxid_get();
                                        nfs_lockdmsg_enqueue(&msgreq);
                                        msgreq.lmr_saved_errno = error;
                                        msgreq.lmr_errno = 0;
                                        msgreq.lmr_answered = 0;
                                        /* reset timeout */
                                        timeo = 2;
                                        /* send cancel request */
                                        continue;
                                }
                                break;
                        }

                        /* warn if we're not getting any response */
                        microuptime(&now);
                        if ((msgreq.lmr_errno != EINPROGRESS) &&
                            (nmp->nm_tprintf_initial_delay != 0) &&
                            ((lastmsg + nmp->nm_tprintf_delay) < now.tv_sec)) {
                                lck_mtx_unlock(&nmp->nm_lock);
                                lastmsg = now.tv_sec;
                                nfs_down(nmp, vfs_context_thread(ctx), 0, NFSSTA_LOCKTIMEO, "lockd not responding");
                                wentdown = 1;
                        } else
                                lck_mtx_unlock(&nmp->nm_lock);

                        if (msgreq.lmr_errno == EINPROGRESS) {
                                /*
                                 * We've got a blocked lock request that we are
                                 * going to retry.  First, we'll want to try to
                                 * send a cancel for the previous request.
                                 *
                                 * Clear errno so if we don't get a response
                                 * to the resend we'll call nfs_down().
                                 * Also reset timeout because we'll expect a
                                 * quick response to the cancel/resend (even if
                                 * it is NLM_BLOCKED).
                                 */
                                msg->lm_flags |= LOCKD_MSG_CANCEL;
                                nfs_lockdmsg_dequeue(&msgreq);
                                msg->lm_xid = nfs_lockxid_get();
                                nfs_lockdmsg_enqueue(&msgreq);
                                msgreq.lmr_saved_errno = msgreq.lmr_errno;
                                msgreq.lmr_errno = 0;
                                msgreq.lmr_answered = 0;
                                timeo = 2;
                                /* send cancel then resend request */
                                continue;
                        }
                        /*
                         * We timed out, so we will resend the request.
                         */
                        timeo *= 2;
                        if (timeo > 60)
                                timeo = 60;
                        /* resend request */
                        continue;
                }

                /* we got a reponse, so the server's lockd is OK */
                nfs_up(VTONMP(vp), vfs_context_thread(ctx), NFSSTA_LOCKTIMEO,
                        wentdown ? "lockd alive again" : NULL);
                wentdown = 0;

                if (msgreq.lmr_errno == EINPROGRESS) {
                        /* got NLM_BLOCKED response */
                        /* need to wait for NLM_GRANTED */
                        timeo = 60;
                        msgreq.lmr_answered = 0;
                        goto wait_for_granted;
                }

                if ((msg->lm_flags & LOCKD_MSG_CANCEL) &&
                    (msgreq.lmr_saved_errno == EINPROGRESS)) {
                        /*
                         * We just got a successful reply to the
                         * cancel of the previous blocked lock request.
                         * Now, go ahead and resend the request.
                         */
                        msg->lm_flags &= ~LOCKD_MSG_CANCEL;
                        nfs_lockdmsg_dequeue(&msgreq);
                        msg->lm_xid = nfs_lockxid_get();
                        nfs_lockdmsg_enqueue(&msgreq);
                        msgreq.lmr_saved_errno = 0;
                        msgreq.lmr_errno = 0;
                        msgreq.lmr_answered = 0;
                        timeo = 2;
                        /* resend request */
                        continue;
                }

                if ((msg->lm_flags & LOCKD_MSG_TEST) && msgreq.lmr_errno == 0) {
                        if (msg->lm_fl.l_type != F_UNLCK) {
                                fl->l_type = msg->lm_fl.l_type;
                                fl->l_pid = msg->lm_fl.l_pid;
                                fl->l_start = msg->lm_fl.l_start;
                                fl->l_len = msg->lm_fl.l_len;
                                fl->l_whence = SEEK_SET;
                        } else
                                fl->l_type = F_UNLCK;
                }

                /*
                 * If the blocked lock request was cancelled.
                 * Restore the error condition from when we
                 * originally bailed on the request.
                 */
                if (msg->lm_flags & LOCKD_MSG_CANCEL) {
                        msg->lm_flags &= ~LOCKD_MSG_CANCEL;
                        error = msgreq.lmr_saved_errno;
                } else
                        error = msgreq.lmr_errno;

                nmp = VTONMP(vp);
                if ((error == ENOTSUP) && nmp && !(nmp->nm_state & NFSSTA_LOCKSWORK)) {
                        /*
                         * We have NO evidence that locks work and lockd
                         * returned ENOTSUP.  Let's take this as a hint
                         * that locks aren't supported and disable them
                         * for this mount.
                         */
                        lck_mtx_lock(&nmp->nm_lock);
                        nmp->nm_flag |= NFSMNT_NOLOCKS;
                        nmp->nm_state &= ~NFSSTA_LOCKTIMEO;
                        lck_mtx_unlock(&nmp->nm_lock);
                        printf("lockd returned ENOTSUP, disabling locks for nfs server: %s\n",
                                vfs_statfs(nmp->nm_mountp)->f_mntfromname);
                }
                if (!error) {
                        /* record that NFS file locking has worked on this mount */
                        if (nmp) {
                                lck_mtx_lock(&nmp->nm_lock);
                                if (!(nmp->nm_state & NFSSTA_LOCKSWORK))
                                        nmp->nm_state |= NFSSTA_LOCKSWORK;
                                lck_mtx_unlock(&nmp->nm_lock);
                        }
                        /*
                         * If we successfully acquired a lock, make sure this pid
                         * is in the nfs_lock_pid hash table so we know we can't
                         * short-circuit unlock requests.
                         */
                        if ((lockpidcheck == ENOENT) &&
                            ((ap->a_op == F_SETLK) || (ap->a_op == F_SETLKW))) {
                                error = nfs_lock_pid_check(p, 1);
                                if (error) {
                                        /*
                                         * We couldn't add the pid to the table,
                                         * so we can no longer trust that a pid
                                         * not in the table has no locks.
                                         */
                                        nfs_lock_pid_hash_trusted = 0;
                                        printf("nfs_vnop_advlock: pid add failed - no longer trusted\n");
                                }
                        }
                }
                break;
        }

        nfs_lockdmsg_dequeue(&msgreq);

        lck_mtx_unlock(nfs_lock_mutex);

        return (error);
}

/*
 * nfslockdans --
 *      NFS advisory byte-level locks answer from the lock daemon.
 */
int
nfslockdans(proc_t p, struct lockd_ans *ansp)
{
        LOCKD_MSG_REQUEST *msgreq;
        int error;

        /* Let root make this call. */
        error = proc_suser(p);
        if (error)
                return (error);

        /* the version should match, or we're out of sync */
        if (ansp->la_version != LOCKD_ANS_VERSION)
                return (EINVAL);

        lck_mtx_lock(nfs_lock_mutex);

        /* try to find the lockd message by transaction id (cookie) */
        msgreq = nfs_lockdmsg_find_by_xid(ansp->la_xid);
        if (ansp->la_flags & LOCKD_ANS_GRANTED) {
                /*
                 * We can't depend on the granted message having our cookie,
                 * so we check the answer against the lockd message found.
                 * If no message was found or it doesn't match the answer,
                 * we look for the lockd message by the answer's lock info.
                 */
                if (!msgreq || nfs_lockdmsg_compare_to_answer(msgreq, ansp))
                        msgreq = nfs_lockdmsg_find_by_answer(ansp);
                /*
                 * We need to make sure this request isn't being cancelled
                 * If it is, we don't want to accept the granted message.
                 */
                if (msgreq && (msgreq->lmr_msg.lm_flags & LOCKD_MSG_CANCEL))
                        msgreq = NULL;
        }
        if (!msgreq) {
                lck_mtx_unlock(nfs_lock_mutex);
                return (EPIPE);
        }

        msgreq->lmr_errno = ansp->la_errno;
        if ((msgreq->lmr_msg.lm_flags & LOCKD_MSG_TEST) && msgreq->lmr_errno == 0) {
                if (ansp->la_flags & LOCKD_ANS_LOCK_INFO) {
                        if (ansp->la_flags & LOCKD_ANS_LOCK_EXCL)
                                msgreq->lmr_msg.lm_fl.l_type = F_WRLCK;
                        else
                                msgreq->lmr_msg.lm_fl.l_type = F_RDLCK;
                        msgreq->lmr_msg.lm_fl.l_pid = ansp->la_pid;
                        msgreq->lmr_msg.lm_fl.l_start = ansp->la_start;
                        msgreq->lmr_msg.lm_fl.l_len = ansp->la_len;
                } else {
                        msgreq->lmr_msg.lm_fl.l_type = F_UNLCK;
                }
        }

        msgreq->lmr_answered = 1;
        lck_mtx_unlock(nfs_lock_mutex);
        wakeup(msgreq);

        return (0);
}