vfs_lockf.c

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lf_clearlock(unlock)
	register struct lockf *unlock;
{
	struct lockf **head = unlock->lf_head;
	register struct lockf *lf = *head;
	struct lockf *overlap, **prev;
	int ovcase;

	if (lf == NOLOCKF)
		return (0);
#ifdef LOCKF_DEBUG
	if (unlock->lf_type != F_UNLCK)
		panic("lf_clearlock: bad type");
	if (lockf_debug & 1)
		lf_print("lf_clearlock", unlock);
#endif /* LOCKF_DEBUG */
	prev = head;
	while ((ovcase = lf_findoverlap(lf, unlock, SELF,
					&prev, &overlap)) != 0) {
		/*
		 * Wakeup the list of locks to be retried.
		 */
		lf_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;
			}
			lf_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)
		lf_printlist("lf_clearlock", unlock);
#endif /* LOCKF_DEBUG */
	return (0);
}

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

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

	if ((block = lf_getblock(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;
		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 inode and
 * return the first blocking lock.
 */
struct lockf *
lf_getblock(lock)
	register struct lockf *lock;
{
	struct lockf **prev, *overlap, *lf = *(lock->lf_head);
	int ovcase;

	prev = lock->lf_head;
	while ((ovcase = lf_findoverlap(lf, lock, OTHERS,
					&prev, &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 = overlap->lf_next;
	}
	return (NOLOCKF);
}

/*
 * 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(lf, lock, type, prev, overlap)
	register struct lockf *lf;
	struct lockf *lock;
	int type;
	struct lockf ***prev;
	struct lockf **overlap;
{
	off_t start, end;

	*overlap = lf;
	if (lf == NOLOCKF)
		return (0);
#ifdef LOCKF_DEBUG
	if (lockf_debug & 2)
		lf_print("lf_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)
			lf_print("\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("lf_findoverlap: default");
	}
	return (0);
}

/*
 * Add a lock to the end of the blocked list.
 */
void
lf_addblock(lock, blocked)
	struct lockf *lock;
	struct lockf *blocked;
{
	register struct lockf *lf;

	if (blocked == NOLOCKF)
		return;
#ifdef LOCKF_DEBUG
	if (lockf_debug & 2) {
		lf_print("addblock: adding", blocked);
		lf_print("to blocked list of", lock);
	}
#endif /* LOCKF_DEBUG */
	if ((lf = lock->lf_block) == NOLOCKF) {
		lock->lf_block = blocked;
		return;
	}
	while (lf->lf_block != NOLOCKF)
		lf = lf->lf_block;
	lf->lf_block = blocked;
	return;
}

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

#ifdef LOCKF_DEBUG
	if (lockf_debug & 2) {
		lf_print("lf_split", lock1);
		lf_print("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 lockf *, sizeof *splitlock, M_LOCKF, M_WAITOK);
	bcopy((caddr_t)lock1, (caddr_t)splitlock, sizeof *splitlock);
	splitlock->lf_start = lock2->lf_end + 1;
	splitlock->lf_block = NOLOCKF;
	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
lf_wakelock(listhead)
	struct lockf *listhead;
{
	register struct lockf *blocklist, *wakelock;

	blocklist = listhead->lf_block;
	listhead->lf_block = NOLOCKF;
	while (blocklist != NOLOCKF) {
		wakelock = blocklist;
		blocklist = blocklist->lf_block;
		wakelock->lf_block = NOLOCKF;
		wakelock->lf_next = NOLOCKF;
#ifdef LOCKF_DEBUG
		if (lockf_debug & 2)
			lf_print("lf_wakelock: awakening", wakelock);
#endif /* LOCKF_DEBUG */
		wakeup((caddr_t)wakelock);
	}
}

#ifdef LOCKF_DEBUG
/*
 * Print out a lock.
 */
void
lf_print(tag, lock)
	char *tag;
	register struct lockf *lock;
{
	
	printf("%s: lock %p 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_inode->i_number,
		major(lock->lf_inode->i_dev),
		minor(lock->lf_inode->i_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_block)
		printf(" block %p\n", lock->lf_block);
	else
		printf("\n");
}

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

	printf("%s: Lock list for ino %d on dev <%d, %d>:\n",
		tag, lock->lf_inode->i_number,
		major(lock->lf_inode->i_dev),
		minor(lock->lf_inode->i_dev));
	for (lf = lock->lf_inode->i_lockf; lf; lf = lf->lf_next) {
		printf("\tlock %p 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);
		if (lf->lf_block)
			printf(" block %p\n", lf->lf_block);
		else
			printf("\n");
	}
}
#endif /* LOCKF_DEBUG */