+/*
+ * Copyright (c) 1982, 1986, 1989 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.
+ *
+ * @(#)ufs_lockf.c 7.7 (Berkeley) 7/2/91
+ */
+
+#include "param.h"
+#include "systm.h"
+#include "kernel.h"
+#include "file.h"
+#include "proc.h"
+#include "vnode.h"
+#include "malloc.h"
+#include "fcntl.h"
+
+#include "lockf.h"
+#include "quota.h"
+#include "inode.h"
+
+/*
+ * This variable controls the maximum number of processes that will
+ * be checked in doing deadlock detection.
+ */
+int maxlockdepth = MAXDEPTH;
+
+#ifdef LOCKF_DEBUG
+int lockf_debug = 0;
+#endif /* LOCKF_DEBUG */
+
+#define NOLOCKF (struct lockf *)0
+#define SELF 0x1
+#define OTHERS 0x2
+
+/*
+ * Set a byte-range lock.
+ */
+lf_setlock(lock)
+ register struct lockf *lock;
+{
+ register struct lockf *block;
+ struct inode *ip = lock->lf_inode;
+ struct lockf **prev, *overlap, *ltmp;
+ static char lockstr[] = "lockf";
+ int ovcase, priority, needtolink, error;
+
+#ifdef LOCKF_DEBUG
+ if (lockf_debug & 1)
+ lf_print("lf_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 = lf_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 lockf *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++ < maxlockdepth)) {
+ waitblock = (struct lockf *)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) 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_next = block;
+ lf_addblock(block, lock);
+#ifdef LOCKF_DEBUG
+ if (lockf_debug & 1) {
+ lf_print("lf_setlock: blocking on", block);
+ lf_printlist("lf_setlock", block);
+ }
+#endif /* LOCKF_DEBUG */
+ if (error = tsleep((caddr_t)lock, priority, lockstr, 0)) {
+ 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 = &ip->i_lockf;
+ block = ip->i_lockf;
+ needtolink = 1;
+ for (;;) {
+ if (ovcase = lf_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)
+ lf_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
+ lf_split(overlap, lock);
+ lf_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) {
+ lf_wakelock(overlap);
+ } else {
+ ltmp = lock->lf_block;
+ lock->lf_block = overlap->lf_block;
+ lf_addblock(lock, ltmp);
+ }
+ /*
+ * 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;
+ lf_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;
+ lf_wakelock(overlap);
+ break;
+ }
+ break;
+ }
+#ifdef LOCKF_DEBUG
+ if (lockf_debug & 1) {
+ lf_print("lf_setlock: got the lock", lock);
+ lf_printlist("lf_setlock", lock);
+ }
+#endif /* LOCKF_DEBUG */
+ 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.
+ */
+lf_clearlock(unlock)
+ register struct lockf *unlock;
+{
+ struct inode *ip = unlock->lf_inode;
+ register struct lockf *lf = ip->i_lockf;
+ 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 = &ip->i_lockf;
+ while (ovcase = lf_findoverlap(lf, unlock, SELF, &prev, &overlap)) {
+ /*
+ * 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.
+ */
+lf_getlock(lock, fl)
+ register struct lockf *lock;
+ register struct flock *fl;
+{
+ register struct lockf *block;
+ off_t start, end;
+
+#ifdef LOCKF_DEBUG
+ if (lockf_debug & 1)
+ lf_print("lf_getlock", lock);
+#endif /* LOCKF_DEBUG */
+
+ if (block = lf_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 inode and
+ * return the first blocking lock.
+ */
+struct lockf *
+lf_getblock(lock)
+ register struct lockf *lock;
+{
+ struct lockf **prev, *overlap, *lf = lock->lf_inode->i_lockf;
+ int ovcase;
+
+ prev = &lock->lf_inode->i_lockf;
+ while (ovcase = lf_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 inode to
+ * find an overlapping lock (if any).
+ *
+ * NOTE: this returns only the FIRST overlapping lock. There
+ * may be more than one.
+ */
+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.
+ */
+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.
+ */
+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
+ */
+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.
+ */
+lf_print(tag, lock)
+ char *tag;
+ register struct lockf *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_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 0x%x\n", lock->lf_block);
+ else
+ printf("\n");
+}
+
+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 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);
+ if (lf->lf_block)
+ printf(" block 0x%x\n", lf->lf_block);
+ else
+ printf("\n");
+ }
+}
+#endif /* LOCKF_DEBUG */
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