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NetBSD/sys/kern/vfs_lockf.c

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/*
* 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.
*
* from: @(#)ufs_lockf.c 7.7 (Berkeley) 7/2/91
* $Id: vfs_lockf.c,v 1.2 1994/04/25 03:49:43 cgd Exp $
*/
#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 <sys/lockf.h>
/*
* Advisory record locking support
*/
lf_advlock(head, size, id, op, fl, flags)
struct lockf **head;
u_quad_t size;
caddr_t id;
int op;
register struct flock *fl;
int flags;
{
register struct lockf *lock;
off_t start, end;
int error;
/*
* Avoid the common case of unlocking when inode has no locks.
*/
if (*head == (struct lockf *)0) {
if (op != F_SETLK) {
fl->l_type = F_UNLCK;
return (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)
end = -1;
else
end = start + fl->l_len - 1;
/*
* Create the lockf structure
*/
MALLOC(lock, struct lockf *, sizeof *lock, M_LOCKF, M_WAITOK);
lock->lf_start = start;
lock->lf_end = end;
lock->lf_id = id;
lock->lf_head = head;
lock->lf_type = fl->l_type;
lock->lf_next = (struct lockf *)0;
lock->lf_block = (struct lockf *)0;
lock->lf_flags = flags;
/*
* Do the requested operation.
*/
switch(op) {
case F_SETLK:
return (lf_setlock(lock));
case F_UNLCK:
error = lf_clearlock(lock);
FREE(lock, M_LOCKF);
return (error);
case F_GETLK:
error = lf_getlock(lock, fl);
FREE(lock, M_LOCKF);
return (error);
default:
free(lock, M_LOCKF);
return (EINVAL);
}
/* NOTREACHED */
}
/*
* 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 lockf **head = lock->lf_head;
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)) {
/*
* Delete ourselves from the waiting to lock list.
*/
for (block = lock->lf_next;
block != NOLOCKF;
block = block->lf_block) {
if (block->lf_block != lock)
continue;
block->lf_block = block->lf_block->lf_block;
free(lock, M_LOCKF);
return (error);
}
panic("lf_setlock: lost lock");
}
}
/*
* 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 = head;
block = *head;
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 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)) {
/*
* 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_head);
int ovcase;
prev = lock->lf_head;
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.
*/
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.
*/
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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