[apple/xnu.git] / bsd / hfs / hfs_lockf.c

/*
 * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This 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 OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

/*      (c) 1997-1998   Apple Computer, Inc.  All Rights Reserved */
/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 *
 *      @(#)hfs_lockf.c 1.0
 *      derived from @(#)ufs_lockf.c    8.4 (Berkeley) 10/26/94
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/file.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/fcntl.h>

#include "hfs_lockf.h"
#include "hfs.h"

/*
 * This variable controls the maximum number of processes that will
 * be checked in doing deadlock detection.
 */
int hfsmaxlockdepth = MAXDEPTH;

#ifdef LOCKF_DEBUG
#include <vm/vm.h>
#include <sys/sysctl.h>
int     lockf_debug = 0;
struct ctldebug debug4 = { "lockf_debug", &lockf_debug };
#endif

#define NOLOCKF (struct hfslockf *)0
#define SELF    0x1
#define OTHERS  0x2

/*
 * Set a byte-range lock.
 */
int
hfs_setlock(lock)
        register struct hfslockf *lock;
{
        register struct hfslockf *block;
        struct hfsnode *hp = lock->lf_hfsnode;
        struct hfslockf **prev, *overlap, *ltmp;
        static char lockstr[] = "hfslockf";
        int ovcase, priority, needtolink, error;

#ifdef LOCKF_DEBUG
        if (lockf_debug & 1)
                hfs_lprint("hfs_setlock", lock);
#endif /* LOCKF_DEBUG */

        /*
         * Set the priority
         */
        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.
         */
        while ((block = hfs_getblock(lock))) {
                /*
                 * Free the structure and return if nonblocking.
                 */
                if ((lock->lf_flags & F_WAIT) == 0) {
                        FREE(lock, M_LOCKF);
                        return (EAGAIN);
                }
                /*
                 * We are blocked. Since flock style locks cover
                 * the whole file, there is no chance for deadlock.
                 * For byte-range locks we must check for deadlock.
                 *
                 * Deadlock detection is done by looking through the
                 * wait channels to see if there are any cycles that
                 * involve us. MAXDEPTH is set just to make sure we
                 * do not go off into neverland.
                 */
                if ((lock->lf_flags & F_POSIX) &&
                    (block->lf_flags & F_POSIX)) {
                        register struct proc *wproc;
                        register struct hfslockf *waitblock;
                        int i = 0;

                        /* The block is waiting on something */
                        wproc = (struct proc *)block->lf_id;
                        while (wproc->p_wchan &&
                               (wproc->p_wmesg == lockstr) &&
                               (i++ < hfsmaxlockdepth)) {
                                waitblock = (struct hfslockf *)wproc->p_wchan;
                                /* Get the owner of the blocking lock */
                                waitblock = waitblock->lf_next;
                                if ((waitblock->lf_flags & F_POSIX) == 0)
                                        break;
                                wproc = (struct proc *)waitblock->lf_id;
                                if (wproc == (struct proc *)lock->lf_id) {
                                        _FREE(lock, M_LOCKF);
                                        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) hfs_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_next = block;
                TAILQ_INSERT_TAIL(&block->lf_blkhd, lock, lf_block);
#ifdef LOCKF_DEBUG
                if (lockf_debug & 1) {
                        hfs_lprint("hfs_setlock: blocking on", block);
                        hfs_lprintlist("hfs_setlock", block);
                }
#endif /* LOCKF_DEBUG */
                if ((error = tsleep((caddr_t)lock, priority, lockstr, 0))) {
                        /*
                         * We may have been awakened by a signal (in
                         * which case we must remove ourselves from the
                         * blocked list) and/or by another process
                         * releasing a lock (in which case we have already
                         * been removed from the blocked list and our
                         * lf_next field set to NOLOCKF).
                         */
                        if (lock->lf_next)
                                TAILQ_REMOVE(&lock->lf_next->lf_blkhd, lock,
                                    lf_block);
                        _FREE(lock, M_LOCKF);
                        return (error);
                }
        }
        /*
         * 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.
         */
        prev = &hp->h_lockf;
        block = hp->h_lockf;
        needtolink = 1;
        for (;;) {
                if ((ovcase = hfs_findoverlap(block, lock, SELF, &prev, &overlap)))
                        block = overlap->lf_next;
                /*
                 * 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) {
                                *prev = lock;
                                lock->lf_next = overlap;
                        }
                        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)
                                hfs_wakelock(overlap);
                        overlap->lf_type = lock->lf_type;
                        FREE(lock, M_LOCKF);
                        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) {
                                _FREE(lock, M_LOCKF);
                                lock = overlap; /* for debug output below */
                                break;
                        }
                        if (overlap->lf_start == lock->lf_start) {
                                *prev = lock;
                                lock->lf_next = overlap;
                                overlap->lf_start = lock->lf_end + 1;
                        } else
                                hfs_split(overlap, lock);
                        hfs_wakelock(overlap);
                        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) {
                                hfs_wakelock(overlap);
                        } else {
                                while ((ltmp = overlap->lf_blkhd.tqh_first)) {
                                        TAILQ_REMOVE(&overlap->lf_blkhd, ltmp,
                                            lf_block);
                                        TAILQ_INSERT_TAIL(&lock->lf_blkhd,
                                            ltmp, lf_block);
                                }
                        }
                        /*
                         * Add the new lock if necessary and delete the overlap.
                         */
                        if (needtolink) {
                                *prev = lock;
                                lock->lf_next = overlap->lf_next;
                                prev = &lock->lf_next;
                                needtolink = 0;
                        } else
                                *prev = overlap->lf_next;
                        _FREE(overlap, M_LOCKF);
                        continue;

                case 4: /* overlap starts before lock */
                        /*
                         * Add lock after overlap on the list.
                         */
                        lock->lf_next = overlap->lf_next;
                        overlap->lf_next = lock;
                        overlap->lf_end = lock->lf_start - 1;
                        prev = &lock->lf_next;
                        hfs_wakelock(overlap);
                        needtolink = 0;
                        continue;

                case 5: /* overlap ends after lock */
                        /*
                         * Add the new lock before overlap.
                         */
                        if (needtolink) {
                                *prev = lock;
                                lock->lf_next = overlap;
                        }
                        overlap->lf_start = lock->lf_end + 1;
                        hfs_wakelock(overlap);
                        break;
                }
                break;
        }
#ifdef LOCKF_DEBUG
        if (lockf_debug & 1) {
                hfs_lprint("hfs_setlock: got the lock", lock);
                hfs_lprintlist("hfs_setlock", lock);
        }
#endif /* LOCKF_DEBUG */
        return (0);
}

/*
 * Remove a byte-range lock on an hfsnode.
 *
 * Generally, find the lock (or an overlap to that lock)
 * and remove it (or shrink it), then wakeup anyone we can.
 */
int
hfs_clearlock(unlock)
        register struct hfslockf *unlock;
{
        struct hfsnode *hp = unlock->lf_hfsnode;
        register struct hfslockf *lf = hp->h_lockf;
        struct hfslockf *overlap, **prev;
        int ovcase;

        if (lf == NOLOCKF)
                return (0);
#ifdef LOCKF_DEBUG
        if (unlock->lf_type != F_UNLCK)
                panic("hfs_clearlock: bad type");
        if (lockf_debug & 1)
                hfs_lprint("hfs_clearlock", unlock);
#endif /* LOCKF_DEBUG */
        prev = &hp->h_lockf;
        while ((ovcase = hfs_findoverlap(lf, unlock, SELF, &prev, &overlap))) {
                /*
                 * Wakeup the list of locks to be retried.
                 */
                hfs_wakelock(overlap);

                switch (ovcase) {

                case 1: /* overlap == lock */
                        *prev = overlap->lf_next;
                        FREE(overlap, M_LOCKF);
                        break;

                case 2: /* overlap contains lock: split it */
                        if (overlap->lf_start == unlock->lf_start) {
                                overlap->lf_start = unlock->lf_end + 1;
                                break;
                        }
                        hfs_split(overlap, unlock);
                        overlap->lf_next = unlock->lf_next;
                        break;

                case 3: /* lock contains overlap */
                        *prev = overlap->lf_next;
                        lf = overlap->lf_next;
                        _FREE(overlap, M_LOCKF);
                        continue;

                case 4: /* overlap starts before lock */
                        overlap->lf_end = unlock->lf_start - 1;
                        prev = &overlap->lf_next;
                        lf = overlap->lf_next;
                        continue;

                case 5: /* overlap ends after lock */
                        overlap->lf_start = unlock->lf_end + 1;
                        break;
                }
                break;
        }
#ifdef LOCKF_DEBUG
        if (lockf_debug & 1)
                hfs_lprintlist("hfs_clearlock", unlock);
#endif /* LOCKF_DEBUG */
        return (0);
}

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

#ifdef LOCKF_DEBUG
        if (lockf_debug & 1)
                hfs_lprint("hfs_getlock", lock);
#endif /* LOCKF_DEBUG */

        if ((block = hfs_getblock(lock))) {
                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;
                if (block->lf_flags & F_POSIX)
                        fl->l_pid = ((struct proc *)(block->lf_id))->p_pid;
                else
                        fl->l_pid = -1;
        } else {
                fl->l_type = F_UNLCK;
        }
        return (0);
}

/*
 * Walk the list of locks for an hfsnode and
 * return the first blocking lock.
 */
struct hfslockf *
hfs_getblock(lock)
        register struct hfslockf *lock;
{
        struct hfslockf **prev, *overlap, *lf = lock->lf_hfsnode->h_lockf;
        int ovcase;

        prev = &lock->lf_hfsnode->h_lockf;
        while ((ovcase = hfs_findoverlap(lf, lock, OTHERS, &prev, &overlap))) {
                /*
                 * 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 = overlap->lf_next;
        }
        return (NOLOCKF);
}

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

        *overlap = lf;
        if (lf == NOLOCKF)
                return (0);
#ifdef LOCKF_DEBUG
        if (lockf_debug & 2)
                hfs_lprint("hfs_findoverlap: looking for overlap in", lock);
#endif /* LOCKF_DEBUG */
        start = lock->lf_start;
        end = lock->lf_end;
        while (lf != NOLOCKF) {
                if (((type & SELF) && lf->lf_id != lock->lf_id) ||
                    ((type & OTHERS) && lf->lf_id == lock->lf_id)) {
                        *prev = &lf->lf_next;
                        *overlap = lf = lf->lf_next;
                        continue;
                }
#ifdef LOCKF_DEBUG
                if (lockf_debug & 2)
                        hfs_lprint("\tchecking", lf);
#endif /* LOCKF_DEBUG */
                /*
                 * 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
                 */
                if ((lf->lf_end != -1 && start > lf->lf_end) ||
                    (end != -1 && lf->lf_start > end)) {
                        /* Case 0 */
#ifdef LOCKF_DEBUG
                        if (lockf_debug & 2)
                                printf("no overlap\n");
#endif /* LOCKF_DEBUG */
                        if ((type & SELF) && end != -1 && lf->lf_start > end)
                                return (0);
                        *prev = &lf->lf_next;
                        *overlap = lf = lf->lf_next;
                        continue;
                }
                if ((lf->lf_start == start) && (lf->lf_end == end)) {
                        /* Case 1 */
#ifdef LOCKF_DEBUG
                        if (lockf_debug & 2)
                                printf("overlap == lock\n");
#endif /* LOCKF_DEBUG */
                        return (1);
                }
                if ((lf->lf_start <= start) &&
                    (end != -1) &&
                    ((lf->lf_end >= end) || (lf->lf_end == -1))) {
                        /* Case 2 */
#ifdef LOCKF_DEBUG
                        if (lockf_debug & 2)
                                printf("overlap contains lock\n");
#endif /* LOCKF_DEBUG */
                        return (2);
                }
                if (start <= lf->lf_start &&
                           (end == -1 ||
                           (lf->lf_end != -1 && end >= lf->lf_end))) {
                        /* Case 3 */
#ifdef LOCKF_DEBUG
                        if (lockf_debug & 2)
                                printf("lock contains overlap\n");
#endif /* LOCKF_DEBUG */
                        return (3);
                }
                if ((lf->lf_start < start) &&
                        ((lf->lf_end >= start) || (lf->lf_end == -1))) {
                        /* Case 4 */
#ifdef LOCKF_DEBUG
                        if (lockf_debug & 2)
                                printf("overlap starts before lock\n");
#endif /* LOCKF_DEBUG */
                        return (4);
                }
                if ((lf->lf_start > start) &&
                        (end != -1) &&
                        ((lf->lf_end > end) || (lf->lf_end == -1))) {
                        /* Case 5 */
#ifdef LOCKF_DEBUG
                        if (lockf_debug & 2)
                                printf("overlap ends after lock\n");
#endif /* LOCKF_DEBUG */
                        return (5);
                }
                panic("hfs_findoverlap: default");
        }
        return (0);
}

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

#ifdef LOCKF_DEBUG
        if (lockf_debug & 2) {
                hfs_lprint("hfs_split", lock1);
                hfs_lprint("splitting from", lock2);
        }
#endif /* LOCKF_DEBUG */
        /*
         * Check to see if spliting into only two pieces.
         */
        if (lock1->lf_start == lock2->lf_start) {
                lock1->lf_start = lock2->lf_end + 1;
                lock2->lf_next = lock1;
                return;
        }
        if (lock1->lf_end == lock2->lf_end) {
                lock1->lf_end = lock2->lf_start - 1;
                lock2->lf_next = lock1->lf_next;
                lock1->lf_next = lock2;
                return;
        }
        /*
         * Make a new lock consisting of the last part of
         * the encompassing lock
         */
        MALLOC(splitlock, struct hfslockf *, sizeof *splitlock, M_LOCKF, M_WAITOK);
        bcopy((caddr_t)lock1, (caddr_t)splitlock, sizeof *splitlock);
        splitlock->lf_start = lock2->lf_end + 1;
        TAILQ_INIT(&splitlock->lf_blkhd);
        lock1->lf_end = lock2->lf_start - 1;
        /*
         * OK, now link it in
         */
        splitlock->lf_next = lock1->lf_next;
        lock2->lf_next = splitlock;
        lock1->lf_next = lock2;
}

/*
 * Wakeup a blocklist
 */
void
hfs_wakelock(listhead)
        struct hfslockf *listhead;
{
        register struct hfslockf *wakelock;

        while ((wakelock = listhead->lf_blkhd.tqh_first)) {
                TAILQ_REMOVE(&listhead->lf_blkhd, wakelock, lf_block);
                wakelock->lf_next = NOLOCKF;
#ifdef LOCKF_DEBUG
                if (lockf_debug & 2)
                        hfs_lprint("hfs_wakelock: awakening", wakelock);
#endif /* LOCKF_DEBUG */
                wakeup((caddr_t)wakelock);
        }
}

#ifdef LOCKF_DEBUG
/*
 * Print out a lock.
 */
hfs_lprint(tag, lock)
        char *tag;
        register struct hfslockf *lock;
{
        
        printf("%s: lock 0x%lx for ", tag, lock);
        if (lock->lf_flags & F_POSIX)
                printf("proc %d", ((struct proc *)(lock->lf_id))->p_pid);
        else
                printf("id 0x%x", lock->lf_id);
        printf(" in ino %d on dev <%d, %d>, %s, start %d, end %d",
                lock->lf_hfsnode->i_number,
                major(lock->lf_hfsnode->h_dev),
                minor(lock->lf_hfsnode->h_dev),
                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);
        if (lock->lf_blkhd.tqh_first)
                printf(" block 0x%x\n", lock->lf_blkhd.tqh_first);
        else
                printf("\n");
}

hfs_lprintlist(tag, lock)
        char *tag;
        struct hfslockf *lock;
{
        register struct hfslockf *lf, *blk;

        printf("%s: Lock list for ino %d on dev <%d, %d>:\n",
                tag, lock->lf_hfsnode->i_number,
                major(lock->lf_hfsnode->h_dev),
                minor(lock->lf_hfsnode->h_dev));
        for (lf = lock->lf_hfsnode->h_lockf; lf; lf = lf->lf_next) {
                printf("\tlock 0x%lx for ", lf);
                if (lf->lf_flags & F_POSIX)
                        printf("proc %d", ((struct proc *)(lf->lf_id))->p_pid);
                else
                        printf("id 0x%x", lf->lf_id);
                printf(", %s, start %d, end %d",
                        lf->lf_type == F_RDLCK ? "shared" :
                        lf->lf_type == F_WRLCK ? "exclusive" :
                        lf->lf_type == F_UNLCK ? "unlock" :
                        "unknown", lf->lf_start, lf->lf_end);
                for (blk = lf->lf_blkhd.tqh_first; blk;
                     blk = blk->lf_block.tqe_next) {
                        printf("\n\t\tlock request 0x%lx for ", blk);
                        if (blk->lf_flags & F_POSIX)
                                printf("proc %d",
                                    ((struct proc *)(blk->lf_id))->p_pid);
                        else
                                printf("id 0x%x", blk->lf_id);
                        printf(", %s, start %d, end %d",
                                blk->lf_type == F_RDLCK ? "shared" :
                                blk->lf_type == F_WRLCK ? "exclusive" :
                                blk->lf_type == F_UNLCK ? "unlock" :
                                "unknown", blk->lf_start, blk->lf_end);
                        if (blk->lf_blkhd.tqh_first)
                                panic("hfs_lprintlist: bad list");
                }
                printf("\n");
        }
}
#endif /* LOCKF_DEBUG */