/*      $OpenBSD: vfs_lockf.c,v 1.50 2022/08/14 01:58:28 jsg Exp $      */
/*      $NetBSD: vfs_lockf.c,v 1.7 1996/02/04 02:18:21 christos Exp $   */

/*
 * Copyright (c) 1982, 1986, 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Scooter Morris at Genentech Inc.
 *
 * 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.
 *
 *      @(#)ufs_lockf.c 8.3 (Berkeley) 1/6/94
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/pool.h>
#include <sys/fcntl.h>
#include <sys/lockf.h>
#include <sys/rwlock.h>
#include <sys/unistd.h>

/*
 * The lockf structure is a kernel structure which contains the information
 * associated with a byte range lock.  The lockf structures are linked into
 * the inode structure. Locks are sorted by the starting byte of the lock for
 * efficiency.
 */
TAILQ_HEAD(locklist, lockf);

struct lockf {
        short   lf_flags;        /* Lock semantics: F_POSIX, F_FLOCK, F_WAIT */
        short   lf_type;         /* Lock type: F_RDLCK, F_WRLCK */
        off_t   lf_start;        /* The byte # of the start of the lock */
        off_t   lf_end;          /* The byte # of the end of the lock (-1=EOF)*/
        caddr_t lf_id;           /* The id of the resource holding the lock */
        struct  lockf_state *lf_state;  /* State associated with the lock */
        TAILQ_ENTRY(lockf) lf_entry;
        struct  lockf *lf_blk;   /* The lock that blocks us */
        struct  locklist lf_blkhd;      /* The list of blocked locks */
        TAILQ_ENTRY(lockf) lf_block; /* A request waiting for a lock */
        uid_t   lf_uid;         /* User ID responsible */
        pid_t   lf_pid;         /* POSIX - owner pid */
};

struct lockf_state {
        TAILQ_HEAD(, lockf)       ls_locks;     /* list of active locks */
        TAILQ_HEAD(, lockf)       ls_pending;   /* list of pending locks */
        struct lockf_state      **ls_owner;     /* owner */
        int                       ls_refs;      /* reference counter */
};

struct pool lockf_state_pool;
struct pool lockf_pool;

#define SELF    0x1
#define OTHERS  0x2

#ifdef LOCKF_DEBUG

#define DEBUG_SETLOCK           0x01
#define DEBUG_CLEARLOCK         0x02
#define DEBUG_GETLOCK           0x04
#define DEBUG_FINDOVR           0x08
#define DEBUG_SPLIT             0x10
#define DEBUG_WAKELOCK          0x20
#define DEBUG_LINK              0x40

int     lockf_debug = DEBUG_SETLOCK|DEBUG_CLEARLOCK|DEBUG_WAKELOCK;

void    lf_print(const char *, struct lockf *);
void    lf_printlist(const char *, struct lockf *);

#define DPRINTF(args, level)    if (lockf_debug & (level)) printf args
#define LFPRINT(args, level)    if (lockf_debug & (level)) lf_print args
#else
#define DPRINTF(args, level)
#define LFPRINT(args, level)
#endif

struct lockf *lf_alloc(uid_t, int);
void lf_free(struct lockf *);
int lf_clearlock(struct lockf *);
int lf_findoverlap(struct lockf *, struct lockf *, int, struct lockf **);
struct lockf *lf_getblock(struct lockf *, struct lockf *);
int lf_getlock(struct lockf *, struct flock *);
int lf_setlock(struct lockf *);
void lf_split(struct lockf *, struct lockf *);
void lf_wakelock(struct lockf *, int);
int lf_deadlock(struct lockf *);
void ls_ref(struct lockf_state *);
void ls_rele(struct lockf_state *);

/*
 * Serializes access to each instance of struct lockf and struct lockf_state
 * and each pointer from a vnode to struct lockf_state.
 */
struct rwlock lockf_lock = RWLOCK_INITIALIZER("lockflk");

void
lf_init(void)
{
        pool_init(&lockf_state_pool, sizeof(struct lockf_state), 0, IPL_NONE,
            PR_WAITOK | PR_RWLOCK, "lockfspl", NULL);
        pool_init(&lockf_pool, sizeof(struct lockf), 0, IPL_NONE,
            PR_WAITOK | PR_RWLOCK, "lockfpl", NULL);
}

void
ls_ref(struct lockf_state *ls)
{
        rw_assert_wrlock(&lockf_lock);

        ls->ls_refs++;
}

void
ls_rele(struct lockf_state *ls)
{
        rw_assert_wrlock(&lockf_lock);

        if (--ls->ls_refs > 0)
                return;

        KASSERT(TAILQ_EMPTY(&ls->ls_locks));
        KASSERT(TAILQ_EMPTY(&ls->ls_pending));

        *ls->ls_owner = NULL;
        pool_put(&lockf_state_pool, ls);
}

/*
 * We enforce a limit on locks by uid, so that a single user cannot
 * run the kernel out of memory.  For now, the limit is pretty coarse.
 * There is no limit on root.
 *
 * Splitting a lock will always succeed, regardless of current allocations.
 * If you're slightly above the limit, we still have to permit an allocation
 * so that the unlock can succeed.  If the unlocking causes too many splits,
 * however, you're totally cutoff.
 */
int maxlocksperuid = 1024;

/*
 * 3 options for allowfail.
 * 0 - always allocate.  1 - cutoff at limit.  2 - cutoff at double limit.
 */
struct lockf *
lf_alloc(uid_t uid, int allowfail)
{
        struct uidinfo *uip;
        struct lockf *lock;

        uip = uid_find(uid);
        if (uid && allowfail && uip->ui_lockcnt >
            (allowfail == 1 ? maxlocksperuid : (maxlocksperuid * 2))) {
                uid_release(uip);
                return (NULL);
        }
        uip->ui_lockcnt++;
        uid_release(uip);
        lock = pool_get(&lockf_pool, PR_WAITOK);
        lock->lf_uid = uid;
        return (lock);
}

void
lf_free(struct lockf *lock)
{
        struct uidinfo *uip;

        rw_assert_wrlock(&lockf_lock);

        LFPRINT(("lf_free", lock), DEBUG_LINK);

        KASSERT(TAILQ_EMPTY(&lock->lf_blkhd));

        ls_rele(lock->lf_state);

        uip = uid_find(lock->lf_uid);
        uip->ui_lockcnt--;
        uid_release(uip);
        pool_put(&lockf_pool, lock);
}


/*
 * Do an advisory lock operation.
 */
int
lf_advlock(struct lockf_state **state, off_t size, caddr_t id, int op,
    struct flock *fl, int flags)
{
        struct proc *p = curproc;
        struct lockf_state *ls;
        struct lockf *lock;
        off_t start, end;
        int error = 0;

        /*
         * 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
                 * when SEEK_CUR is used.
                 */
                start = fl->l_start;
                break;
        case SEEK_END:
                start = size + fl->l_start;
                break;
        default:
                return (EINVAL);
        }
        if (start < 0)
                return (EINVAL);
        if (fl->l_len > 0) {
                if (fl->l_len - 1 > LLONG_MAX - start)
                        return (EOVERFLOW);
                end = start + (fl->l_len - 1);
                /* Avoid ambiguity at the end of the range. */
                if (end == LLONG_MAX)
                        end = -1;
        } else if (fl->l_len < 0) {
                if (start + fl->l_len < 0)
                        return (EINVAL);
                end = start - 1;
                start += fl->l_len;
        } else {
                end = -1;
        }

        rw_enter_write(&lockf_lock);
        ls = *state;

        /*
         * Avoid the common case of unlocking when inode has no locks.
         */
        if (ls == NULL && op != F_SETLK) {
                fl->l_type = F_UNLCK;
                goto out;
        }

        if (ls == NULL) {
                ls = pool_get(&lockf_state_pool, PR_WAITOK | PR_ZERO);
                ls->ls_owner = state;
                TAILQ_INIT(&ls->ls_locks);
                TAILQ_INIT(&ls->ls_pending);
                *state = ls;
        }
        ls_ref(ls);

        lock = lf_alloc(p->p_ucred->cr_uid, op == F_SETLK ? 1 : 2);
        if (!lock) {
                ls_rele(ls);
                error = ENOLCK;
                goto out;
        }
        lock->lf_flags = flags;
        lock->lf_type = fl->l_type;
        lock->lf_start = start;
        lock->lf_end = end;
        lock->lf_id = id;
        lock->lf_state = ls;
        lock->lf_blk = NULL;
        lock->lf_pid = (flags & F_POSIX) ? p->p_p->ps_pid : -1;
        TAILQ_INIT(&lock->lf_blkhd);

        switch (op) {
        case F_SETLK:
                error = lf_setlock(lock);
                break;
        case F_UNLCK:
                error = lf_clearlock(lock);
                lf_free(lock);
                break;
        case F_GETLK:
                error = lf_getlock(lock, fl);
                lf_free(lock);
                break;
        default:
                lf_free(lock);
                error = EINVAL;
                break;
        }

out:
        rw_exit_write(&lockf_lock);
        return (error);
}

/*
 * Set a byte-range lock.
 */
int
lf_setlock(struct lockf *lock)
{
        struct lockf *block;
        struct lockf *overlap, *ltmp;
        int ovcase, priority, needtolink, error;

        rw_assert_wrlock(&lockf_lock);

        LFPRINT(("lf_setlock", lock), DEBUG_SETLOCK);

        priority = PLOCK;
        if (lock->lf_type == F_WRLCK)
                priority += 4;
        priority |= PCATCH;
        /*
         * Scan lock list for this file looking for locks that would block us.
         */
        for (;;) {
                block = lf_getblock(TAILQ_FIRST(&lock->lf_state->ls_locks),
                    lock);
                if (block == NULL)
                        break;

                if ((lock->lf_flags & F_WAIT) == 0) {
                        lf_free(lock);
                        return (EAGAIN);
                }

                /*
                 * Lock is blocked, check for deadlock before proceeding.
                 * Note: flock style locks cover the whole file, there is no
                 * chance for deadlock.
                 */
                if ((lock->lf_flags & F_POSIX) && lf_deadlock(lock)) {
                        lf_free(lock);
                        return (EDEADLK);
                }

                /*
                 * For flock type locks, we must first remove
                 * any shared locks that we hold before we sleep
                 * waiting for an exclusive lock.
                 */
                if ((lock->lf_flags & F_FLOCK) && lock->lf_type == F_WRLCK) {
                        lock->lf_type = F_UNLCK;
                        (void)lf_clearlock(lock);
                        lock->lf_type = F_WRLCK;
                }
                /*
                 * Add our lock to the blocked list and sleep until we're free.
                 * Remember who blocked us (for deadlock detection).
                 */
                lock->lf_blk = block;
                LFPRINT(("lf_setlock", lock), DEBUG_SETLOCK);
                LFPRINT(("lf_setlock: blocking on", block), DEBUG_SETLOCK);
                TAILQ_INSERT_TAIL(&block->lf_blkhd, lock, lf_block);
                TAILQ_INSERT_TAIL(&lock->lf_state->ls_pending, lock, lf_entry);
                error = rwsleep_nsec(lock, &lockf_lock, priority, "lockf",
                    INFSLP);
                TAILQ_REMOVE(&lock->lf_state->ls_pending, lock, lf_entry);
                wakeup_one(lock->lf_state);
                if (lock->lf_blk != NULL) {
                        TAILQ_REMOVE(&lock->lf_blk->lf_blkhd, lock, lf_block);
                        lock->lf_blk = NULL;
                }
                if (error) {
                        lf_free(lock);
                        return (error);
                }
                if (lock->lf_flags & F_INTR) {
                        lf_free(lock);
                        return (EINTR);
                }
        }
        /*
         * No blocks!!  Add the lock.  Note that we will
         * downgrade or upgrade any overlapping locks this
         * process already owns.
         *
         * Skip over locks owned by other processes.
         * Handle any locks that overlap and are owned by ourselves.
         */
        block = TAILQ_FIRST(&lock->lf_state->ls_locks);
        overlap = NULL;
        needtolink = 1;
        for (;;) {
                ovcase = lf_findoverlap(block, lock, SELF, &overlap);
                if (ovcase)
                        block = TAILQ_NEXT(overlap, lf_entry);
                /*
                 * Six cases:
                 *      0) no overlap
                 *      1) overlap == lock
                 *      2) overlap contains lock
                 *      3) lock contains overlap
                 *      4) overlap starts before lock
                 *      5) overlap ends after lock
                 */
                switch (ovcase) {
                case 0: /* no overlap */
                        if (needtolink) {
                                if (overlap)    /* insert before overlap */
                                        TAILQ_INSERT_BEFORE(overlap, lock,
                                            lf_entry);
                                else            /* first or last lock in list */
                                        TAILQ_INSERT_TAIL(&lock->lf_state->ls_locks,
                                            lock, lf_entry);
                        }
                        break;
                case 1: /* overlap == lock */
                        /*
                         * If downgrading lock, others may be
                         * able to acquire it.
                         */
                        if (lock->lf_type == F_RDLCK &&
                            overlap->lf_type == F_WRLCK)
                                lf_wakelock(overlap, 0);
                        overlap->lf_type = lock->lf_type;
                        lf_free(lock);
                        lock = overlap; /* for debug output below */
                        break;
                case 2: /* overlap contains lock */
                        /*
                         * Check for common starting point and different types.
                         */
                        if (overlap->lf_type == lock->lf_type) {
                                if (!needtolink)
                                        TAILQ_REMOVE(&lock->lf_state->ls_locks,
                                            lock, lf_entry);
                                lf_free(lock);
                                lock = overlap; /* for debug output below */
                                break;
                        }
                        if (overlap->lf_start == lock->lf_start) {
                                if (!needtolink)
                                        TAILQ_REMOVE(&lock->lf_state->ls_locks,
                                            lock, lf_entry);
                                TAILQ_INSERT_BEFORE(overlap, lock, lf_entry);
                                overlap->lf_start = lock->lf_end + 1;
                        } else
                                lf_split(overlap, lock);
                        lf_wakelock(overlap, 0);
                        break;
                case 3: /* lock contains overlap */
                        /*
                         * If downgrading lock, others may be able to
                         * acquire it, otherwise take the list.
                         */
                        if (lock->lf_type == F_RDLCK &&
                            overlap->lf_type == F_WRLCK) {
                                lf_wakelock(overlap, 0);
                        } else {
                                while ((ltmp =
                                    TAILQ_FIRST(&overlap->lf_blkhd))) {
                                        TAILQ_REMOVE(&overlap->lf_blkhd, ltmp,
                                            lf_block);
                                        ltmp->lf_blk = lock;
                                        TAILQ_INSERT_TAIL(&lock->lf_blkhd,
                                            ltmp, lf_block);
                                }
                        }
                        /*
                         * Add the new lock if necessary and delete the overlap.
                         */
                        if (needtolink) {
                                TAILQ_INSERT_BEFORE(overlap, lock, lf_entry);
                                needtolink = 0;
                        }
                        TAILQ_REMOVE(&lock->lf_state->ls_locks, overlap, lf_entry);
                        lf_free(overlap);
                        continue;
                case 4: /* overlap starts before lock */
                        /*
                         * Add lock after overlap on the list.
                         */
                        if (!needtolink)
                                TAILQ_REMOVE(&lock->lf_state->ls_locks, lock,
                                    lf_entry);
                        TAILQ_INSERT_AFTER(&lock->lf_state->ls_locks, overlap,
                            lock, lf_entry);
                        overlap->lf_end = lock->lf_start - 1;
                        lf_wakelock(overlap, 0);
                        needtolink = 0;
                        continue;
                case 5: /* overlap ends after lock */
                        /*
                         * Add the new lock before overlap.
                         */
                        if (needtolink)
                                TAILQ_INSERT_BEFORE(overlap, lock, lf_entry);
                        overlap->lf_start = lock->lf_end + 1;
                        lf_wakelock(overlap, 0);
                        break;
                }
                break;
        }
        LFPRINT(("lf_setlock: got the lock", lock), DEBUG_SETLOCK);
        return (0);
}

/*
 * Remove a byte-range lock on an inode.
 *
 * Generally, find the lock (or an overlap to that lock)
 * and remove it (or shrink it), then wakeup anyone we can.
 */
int
lf_clearlock(struct lockf *lock)
{
        struct lockf *lf, *overlap;
        int ovcase;

        rw_assert_wrlock(&lockf_lock);

        lf = TAILQ_FIRST(&lock->lf_state->ls_locks);
        if (lf == NULL)
                return (0);

        LFPRINT(("lf_clearlock", lock), DEBUG_CLEARLOCK);
        while ((ovcase = lf_findoverlap(lf, lock, SELF, &overlap))) {
                lf_wakelock(overlap, 0);

                switch (ovcase) {
                case 1: /* overlap == lock */
                        TAILQ_REMOVE(&lock->lf_state->ls_locks, overlap,
                            lf_entry);
                        lf_free(overlap);
                        break;
                case 2: /* overlap contains lock: split it */
                        if (overlap->lf_start == lock->lf_start) {
                                overlap->lf_start = lock->lf_end + 1;
                                break;
                        }
                        lf_split(overlap, lock);
                        /*
                         * The lock is now part of the list, lf_clearlock() must
                         * ensure that the lock remains detached from the list.
                         */
                        TAILQ_REMOVE(&lock->lf_state->ls_locks, lock, lf_entry);
                        break;
                case 3: /* lock contains overlap */
                        lf = TAILQ_NEXT(overlap, lf_entry);
                        TAILQ_REMOVE(&lock->lf_state->ls_locks, overlap,
                            lf_entry);
                        lf_free(overlap);
                        continue;
                case 4: /* overlap starts before lock */
                        overlap->lf_end = lock->lf_start - 1;
                        lf = TAILQ_NEXT(overlap, lf_entry);
                        continue;
                case 5: /* overlap ends after lock */
                        overlap->lf_start = lock->lf_end + 1;
                        break;
                }
                break;
        }
        return (0);
}

/*
 * Check whether there is a blocking lock,
 * and if so return its process identifier.
 */
int
lf_getlock(struct lockf *lock, struct flock *fl)
{
        struct lockf *block, *lf;

        rw_assert_wrlock(&lockf_lock);

        LFPRINT(("lf_getlock", lock), DEBUG_CLEARLOCK);

        lf = TAILQ_FIRST(&lock->lf_state->ls_locks);
        if ((block = lf_getblock(lf, lock)) != NULL) {
                fl->l_type = block->lf_type;
                fl->l_whence = SEEK_SET;
                fl->l_start = block->lf_start;
                if (block->lf_end == -1)
                        fl->l_len = 0;
                else
                        fl->l_len = block->lf_end - block->lf_start + 1;
                fl->l_pid = block->lf_pid;
        } else {
                fl->l_type = F_UNLCK;
        }
        return (0);
}

/*
 * Walk the list of locks for an inode and
 * return the first blocking lock.
 */
struct lockf *
lf_getblock(struct lockf *lf, struct lockf *lock)
{
        struct lockf *overlap;

        rw_assert_wrlock(&lockf_lock);

        while (lf_findoverlap(lf, lock, OTHERS, &overlap) != 0) {
                /*
                 * We've found an overlap, see if it blocks us
                 */
                if ((lock->lf_type == F_WRLCK || overlap->lf_type == F_WRLCK))
                        return (overlap);
                /*
                 * Nope, point to the next one on the list and
                 * see if it blocks us
                 */
                lf = TAILQ_NEXT(overlap, lf_entry);
        }
        return (NULL);
}

/*
 * Walk the list of locks for an inode to
 * find an overlapping lock (if any).
 *
 * NOTE: this returns only the FIRST overlapping lock.  There
 *       may be more than one.
 */
int
lf_findoverlap(struct lockf *lf, struct lockf *lock, int type,
    struct lockf **overlap)
{
        off_t start, end;

        rw_assert_wrlock(&lockf_lock);

        LFPRINT(("lf_findoverlap: looking for overlap in", lock), DEBUG_FINDOVR);

        *overlap = lf;
        start = lock->lf_start;
        end = lock->lf_end;
        while (lf != NULL) {
                if (((type & SELF) && lf->lf_id != lock->lf_id) ||
                    ((type & OTHERS) && lf->lf_id == lock->lf_id)) {
                        *overlap = lf = TAILQ_NEXT(lf, lf_entry);
                        continue;
                }
                LFPRINT(("\tchecking", lf), DEBUG_FINDOVR);
                /*
                 * OK, check for overlap
                 *
                 * Six cases:
                 *      0) no overlap
                 *      1) overlap == lock
                 *      2) overlap contains lock
                 *      3) lock contains overlap
                 *      4) overlap starts before lock
                 *      5) overlap ends after lock
                 */

                /* Case 0 */
                if ((lf->lf_end != -1 && start > lf->lf_end) ||
                    (end != -1 && lf->lf_start > end)) {
                        DPRINTF(("no overlap\n"), DEBUG_FINDOVR);
                        if ((type & SELF) && end != -1 && lf->lf_start > end)
                                return (0);
                        *overlap = lf = TAILQ_NEXT(lf, lf_entry);
                        continue;
                }
                /* Case 1 */
                if ((lf->lf_start == start) && (lf->lf_end == end)) {
                        DPRINTF(("overlap == lock\n"), DEBUG_FINDOVR);
                        return (1);
                }
                /* Case 2 */
                if ((lf->lf_start <= start) &&
                    (lf->lf_end == -1 || (end != -1 && lf->lf_end >= end))) {
                        DPRINTF(("overlap contains lock\n"), DEBUG_FINDOVR);
                        return (2);
                }
                /* Case 3 */
                if (start <= lf->lf_start &&
                    (end == -1 || (lf->lf_end != -1 && end >= lf->lf_end))) {
                        DPRINTF(("lock contains overlap\n"), DEBUG_FINDOVR);
                        return (3);
                }
                /* Case 4 */
                if ((lf->lf_start < start) &&
                    ((lf->lf_end >= start) || (lf->lf_end == -1))) {
                        DPRINTF(("overlap starts before lock\n"),
                            DEBUG_FINDOVR);
                        return (4);
                }
                /* Case 5 */
                if ((lf->lf_start > start) && (end != -1) &&
                    ((lf->lf_end > end) || (lf->lf_end == -1))) {
                        DPRINTF(("overlap ends after lock\n"), DEBUG_FINDOVR);
                        return (5);
                }
                panic("lf_findoverlap: default");
        }
        return (0);
}

/*
 * Purge all locks associated with the given lock state.
 */
void
lf_purgelocks(struct lockf_state **state)
{
        struct lockf_state *ls;
        struct lockf *lock;

        rw_enter_write(&lockf_lock);

        ls = *state;
        if (ls == NULL)
                goto out;

        ls_ref(ls);

        /* Interrupt blocked locks and wait for all of them to finish. */
        TAILQ_FOREACH(lock, &ls->ls_locks, lf_entry) {
                LFPRINT(("lf_purgelocks: wakeup", lock), DEBUG_SETLOCK);
                lf_wakelock(lock, F_INTR);
        }
        while (!TAILQ_EMPTY(&ls->ls_pending))
                rwsleep_nsec(ls, &lockf_lock, PLOCK, "lockfp", INFSLP);

        /*
         * Any remaining locks cannot block other locks at this point and can
         * safely be removed.
         */
        while ((lock = TAILQ_FIRST(&ls->ls_locks))) {
                TAILQ_REMOVE(&ls->ls_locks, lock, lf_entry);
                lf_free(lock);
        }

        /* This is the last expected thread to hold a lock state reference. */
        KASSERT(ls->ls_refs == 1);
        ls_rele(ls);

out:
        rw_exit_write(&lockf_lock);
}

/*
 * Split a lock and a contained region into
 * two or three locks as necessary.
 */
void
lf_split(struct lockf *lock1, struct lockf *lock2)
{
        struct lockf *splitlock;

        rw_assert_wrlock(&lockf_lock);

        LFPRINT(("lf_split", lock1), DEBUG_SPLIT);
        LFPRINT(("splitting from", lock2), DEBUG_SPLIT);

        /*
         * Check to see if splitting into only two pieces.
         */
        if (lock1->lf_start == lock2->lf_start) {
                lock1->lf_start = lock2->lf_end + 1;
                TAILQ_INSERT_BEFORE(lock1, lock2, lf_entry);
                return;
        }
        if (lock1->lf_end == lock2->lf_end) {
                lock1->lf_end = lock2->lf_start - 1;
                TAILQ_INSERT_AFTER(&lock1->lf_state->ls_locks, lock1, lock2,
                    lf_entry);
                return;
        }
        /*
         * Make a new lock consisting of the last part of
         * the encompassing lock
         */
        splitlock = lf_alloc(lock1->lf_uid, 0);
        splitlock->lf_flags = lock1->lf_flags;
        splitlock->lf_type = lock1->lf_type;
        splitlock->lf_start = lock2->lf_end + 1;
        splitlock->lf_end = lock1->lf_end;
        splitlock->lf_id = lock1->lf_id;
        splitlock->lf_state = lock1->lf_state;
        splitlock->lf_blk = NULL;
        splitlock->lf_pid = lock1->lf_pid;
        TAILQ_INIT(&splitlock->lf_blkhd);
        ls_ref(splitlock->lf_state);
        lock1->lf_end = lock2->lf_start - 1;

        TAILQ_INSERT_AFTER(&lock1->lf_state->ls_locks, lock1, lock2, lf_entry);
        TAILQ_INSERT_AFTER(&lock1->lf_state->ls_locks, lock2, splitlock,
            lf_entry);
}

/*
 * Wakeup a blocklist
 */
void
lf_wakelock(struct lockf *lock, int flags)
{
        struct lockf *wakelock;

        rw_assert_wrlock(&lockf_lock);

        while ((wakelock = TAILQ_FIRST(&lock->lf_blkhd))) {
                TAILQ_REMOVE(&lock->lf_blkhd, wakelock, lf_block);
                wakelock->lf_blk = NULL;
                wakelock->lf_flags |= flags;
                wakeup_one(wakelock);
        }
}

/*
 * Returns non-zero if the given lock would cause a deadlock.
 */
int
lf_deadlock(struct lockf *lock)
{
        struct lockf *block, *lf, *pending;

        lf = TAILQ_FIRST(&lock->lf_state->ls_locks);
        for (; (block = lf_getblock(lf, lock)) != NULL;
            lf = TAILQ_NEXT(block, lf_entry)) {
                if ((block->lf_flags & F_POSIX) == 0)
                        continue;

                TAILQ_FOREACH(pending, &lock->lf_state->ls_pending, lf_entry) {
                        if (pending->lf_blk == NULL)
                                continue; /* lock already unblocked */

                        if (pending->lf_pid == block->lf_pid &&
                            pending->lf_blk->lf_pid == lock->lf_pid)
                                return (1);
                }
        }

        return (0);
}

#ifdef LOCKF_DEBUG
/*
 * Print out a lock.
 */
void
lf_print(const char *tag, struct lockf *lock)
{
        struct lockf    *block;

        if (tag)
                printf("%s: ", tag);
        printf("lock %p", lock);
        if (lock == NULL) {
                printf("\n");
                return;
        }
        printf(", %s %p %s, start %lld, end %lld",
                lock->lf_flags & F_POSIX ? "posix" : "flock",
                lock->lf_id,
                lock->lf_type == F_RDLCK ? "shared" :
                lock->lf_type == F_WRLCK ? "exclusive" :
                lock->lf_type == F_UNLCK ? "unlock" :
                "unknown", lock->lf_start, lock->lf_end);
        printf(", next %p, state %p",
            TAILQ_NEXT(lock, lf_entry), lock->lf_state);
        block = TAILQ_FIRST(&lock->lf_blkhd);
        if (block)
                printf(", block");
        TAILQ_FOREACH(block, &lock->lf_blkhd, lf_block)
                printf(" %p,", block);
        printf("\n");
}

void
lf_printlist(const char *tag, struct lockf *lock)
{
        struct lockf *lf;

        printf("%s: Lock list:\n", tag);
        TAILQ_FOREACH(lf, &lock->lf_state->ls_locks, lf_entry) {
                if (lock == lf)
                        printf(" * ");
                else
                        printf("   ");
                lf_print(NULL, lf);
        }
}
#endif /* LOCKF_DEBUG */