2 * Copyright (c) 1998,1999 Adrian Sun (asun@zoology.washington.edu)
3 * All Rights Reserved. See COPYRIGHT for more information.
5 * Byte-range locks. This uses either whole-file flocks to fake byte
6 * locks or fcntl-based actual byte locks. Because fcntl locks are
7 * process-oriented, we need to keep around a list of file descriptors
8 * that refer to the same file. Currently, this doesn't serialize access
9 * to the locks. as a result, there's the potential for race conditions.
11 * TODO: fix the race when reading/writing.
12 * keep a pool of both locks and reference counters around so that
13 * we can save on mallocs. we should also use a tree to keep things
19 #endif /* HAVE_CONFIG_H */
21 #include <atalk/adouble.h>
31 /* translate between ADLOCK styles and specific locking mechanisms */
32 #define XLATE_FLOCK(type) ((type) == ADLOCK_RD ? LOCK_SH : \
33 ((type) == ADLOCK_WR ? LOCK_EX : \
34 ((type) == ADLOCK_CLR ? LOCK_UN : -1)))
36 #ifdef DISABLE_LOCKING
37 #define fcntl(a, b, c ) (0)
40 /* ----------------------- */
41 static int set_lock(int fd, int cmd, struct flock *lock)
44 /* We assign fd = -2 for symlinks -> do nothing */
46 lock->l_type = F_UNLCK;
49 return fcntl(fd, cmd, lock);
52 /* ----------------------- */
53 static int XLATE_FCNTL_LOCK(int type)
66 /* ----------------------- */
67 static int OVERLAP(off_t a, off_t alen, off_t b, off_t blen)
69 return (!alen && a <= b) ||
71 ( (a + alen > b) && (b + blen > a) );
74 /* allocation for lock regions. we allocate aggressively and shrink
75 * only in large chunks. */
76 #define ARRAY_BLOCK_SIZE 10
77 #define ARRAY_FREE_DELTA 100
79 /* remove a lock and compact space if necessary */
80 static void adf_freelock(struct ad_fd *ad, const int i)
83 adf_lock_t *lock = ad->adf_lock + i;
85 if (--(*lock->refcount) < 1) {
88 lock->lock.l_type = F_UNLCK;
89 set_lock(ad->adf_fd, F_SETLK, &lock->lock); /* unlock */
95 /* move another lock into the empty space */
96 if (i < ad->adf_lockcount) {
97 memcpy(lock, lock + ad->adf_lockcount - i, sizeof(adf_lock_t));
100 /* free extra cruft if we go past a boundary. we always want to
101 * keep at least some stuff around for allocations. this wastes
102 * a bit of space to save time on reallocations. */
103 if ((ad->adf_lockmax > ARRAY_FREE_DELTA) &&
104 (ad->adf_lockcount + ARRAY_FREE_DELTA < ad->adf_lockmax)) {
105 struct adf_lock_t *tmp;
107 tmp = (struct adf_lock_t *)
108 realloc(ad->adf_lock, sizeof(adf_lock_t)*
109 (ad->adf_lockcount + ARRAY_FREE_DELTA));
112 ad->adf_lockmax = ad->adf_lockcount + ARRAY_FREE_DELTA;
119 /* this needs to deal with the following cases:
120 * 1) fork is the only user of the lock
121 * 2) fork shares a read lock with another open fork
123 * i converted to using arrays of locks. everytime a lock
124 * gets removed, we shift all of the locks down.
126 static void adf_unlock(struct ad_fd *ad, const int fork)
129 adf_lock_t *lock = ad->adf_lock;
132 for (i = 0; i < ad->adf_lockcount; i++) {
134 if (lock[i].user == fork) {
135 /* we're really going to delete this lock. note: read locks
136 are the only ones that allow refcounts > 1 */
138 i--; /* we shifted things down, so we need to backtrack */
139 /* unlikely but realloc may have change adf_lock */
146 /* relock any byte lock that overlaps off/len. unlock everything
148 static void adf_relockrange(struct ad_fd *ad, int fd, off_t off, off_t len)
151 adf_lock_t *lock = ad->adf_lock;
154 if (!ad->adf_excl) for (i = 0; i < ad->adf_lockcount; i++) {
155 if (OVERLAP(off, len, lock[i].lock.l_start, lock[i].lock.l_len))
156 set_lock(fd, F_SETLK, &lock[i].lock);
162 /* find a byte lock that overlaps off/len for a particular open fork */
163 static int adf_findlock(struct ad_fd *ad,
164 const int fork, const int type,
169 adf_lock_t *lock = ad->adf_lock;
172 for (i = 0; i < ad->adf_lockcount; i++) {
173 if ((((type & ADLOCK_RD) && (lock[i].lock.l_type == F_RDLCK)) ||
174 ((type & ADLOCK_WR) && (lock[i].lock.l_type == F_WRLCK))) &&
175 (lock[i].user == fork) &&
176 OVERLAP(off, len, lock[i].lock.l_start, lock[i].lock.l_len)) {
185 /* search other fork lock lists */
186 static int adf_findxlock(struct ad_fd *ad,
187 const int fork, const int type,
192 adf_lock_t *lock = ad->adf_lock;
195 for (i = 0; i < ad->adf_lockcount; i++) {
196 if ((((type & ADLOCK_RD) && (lock[i].lock.l_type == F_RDLCK)) ||
197 ((type & ADLOCK_WR) && (lock[i].lock.l_type == F_WRLCK))) &&
198 (lock[i].user != fork) &&
199 OVERLAP(off, len, lock[i].lock.l_start, lock[i].lock.l_len))
206 /* okay, this needs to do the following:
207 * 1) check current list of locks. error on conflict.
208 * 2) apply the lock. error on conflict with another process.
209 * 3) update the list of locks this file has.
211 * NOTE: this treats synchronization locks a little differently. we
212 * do the following things for those:
213 * 1) if the header file exists, all the locks go in the beginning
215 * 2) if the header file doesn't exist, we stick the locks
216 * in the locations specified by AD_FILELOCK_RD/WR.
218 #define LOCK_DATA_WR (0)
219 #define LOCK_DATA_RD (1)
220 #define LOCK_RSRC_WR (2)
221 #define LOCK_RSRC_RD (3)
223 #define LOCK_RSRC_DRD (4)
224 #define LOCK_RSRC_DWR (5)
225 #define LOCK_DATA_DRD (6)
226 #define LOCK_DATA_DWR (7)
228 #define LOCK_RSRC_NONE (8)
229 #define LOCK_DATA_NONE (9)
232 translate a data fork lock to an offset
235 static off_t df2off(int off)
238 if (off == AD_FILELOCK_OPEN_WR)
239 start = LOCK_DATA_WR;
240 else if (off == AD_FILELOCK_OPEN_RD)
241 start = LOCK_DATA_RD;
242 else if (off == AD_FILELOCK_DENY_RD)
243 start = LOCK_DATA_DRD;
244 else if (off == AD_FILELOCK_DENY_WR)
245 start = LOCK_DATA_DWR;
246 else if (off == AD_FILELOCK_OPEN_NONE)
247 start = LOCK_DATA_NONE;
252 translate a resource fork lock to an offset
255 static off_t hf2off(int off)
258 if (off == AD_FILELOCK_OPEN_WR)
259 start = LOCK_RSRC_WR;
260 else if (off == AD_FILELOCK_OPEN_RD)
261 start = LOCK_RSRC_RD;
262 else if (off == AD_FILELOCK_DENY_RD)
263 start = LOCK_RSRC_DRD;
264 else if (off == AD_FILELOCK_DENY_WR)
265 start = LOCK_RSRC_DWR;
266 else if (off == AD_FILELOCK_OPEN_NONE)
267 start = LOCK_RSRC_NONE;
271 /* ------------------ */
272 int ad_fcntl_lock(struct adouble *ad, const u_int32_t eid, const int locktype,
273 const off_t off, const off_t len, const int fork)
285 if (eid == ADEID_DFORK) {
286 adf = &ad->ad_data_fork;
287 if ((type & ADLOCK_FILELOCK)) {
288 if (ad_meta_fileno(ad) != -1) { /* META */
290 lock.l_start = df2off(off);
294 if (ad_meta_fileno(ad) == -1 || ad_reso_fileno(ad) == -1) {
295 /* there's no meta data. return a lock error
296 * otherwise if a second process is able to create it
302 if (type & ADLOCK_FILELOCK) {
303 adf = ad->ad_md; /* either resource or meta data (set in ad_open) */
304 lock.l_start = hf2off(off);
307 /* we really want the resource fork it's a byte lock */
308 adf = &ad->ad_resource_fork;
309 lock.l_start += ad_getentryoff(ad, eid);
312 /* NOTE: we can't write lock a read-only file. on those, we just
313 * make sure that we have a read lock set. that way, we at least prevent
314 * someone else from really setting a deny read/write on the file.
316 if (!(adf->adf_flags & O_RDWR) && (type & ADLOCK_WR)) {
317 type = (type & ~ADLOCK_WR) | ADLOCK_RD;
320 lock.l_type = XLATE_FCNTL_LOCK(type & ADLOCK_MASK);
321 lock.l_whence = SEEK_SET;
324 /* byte_lock(len=-1) lock whole file */
325 if (len == BYTELOCK_MAX) {
326 lock.l_len -= lock.l_start; /* otherwise EOVERFLOW error */
329 /* see if it's locked by another fork.
330 * NOTE: this guarantees that any existing locks must be at most
331 * read locks. we use ADLOCK_WR/RD because F_RD/WRLCK aren't
332 * guaranteed to be ORable. */
333 if (adf_findxlock(adf, fork, ADLOCK_WR |
334 ((type & ADLOCK_WR) ? ADLOCK_RD : 0),
335 lock.l_start, lock.l_len) > -1) {
340 /* look for any existing lock that we may have */
341 i = adf_findlock(adf, fork, ADLOCK_RD | ADLOCK_WR, lock.l_start, lock.l_len);
342 adflock = (i < 0) ? NULL : adf->adf_lock + i;
344 /* here's what we check for:
345 1) we're trying to re-lock a lock, but we didn't specify an update.
346 2) we're trying to free only part of a lock.
347 3) we're trying to free a non-existent lock. */
348 if ( (!adflock && (lock.l_type == F_UNLCK))
351 && !(type & ADLOCK_UPGRADE)
352 && ((lock.l_type != F_UNLCK)
353 || (adflock->lock.l_start != lock.l_start)
354 || (adflock->lock.l_len != lock.l_len) ))
361 /* now, update our list of locks */
363 if (lock.l_type == F_UNLCK) {
364 adf_freelock(adf, i);
368 /* attempt to lock the file. */
369 if (!adf->adf_excl && set_lock(adf->adf_fd, F_SETLK, &lock) < 0)
372 /* we upgraded this lock. */
373 if (adflock && (type & ADLOCK_UPGRADE)) {
374 memcpy(&adflock->lock, &lock, sizeof(lock));
378 /* it wasn't an upgrade */
380 if (lock.l_type == F_RDLCK) {
381 oldlock = adf_findxlock(adf, fork, ADLOCK_RD, lock.l_start, lock.l_len);
384 /* no more space. this will also happen if lockmax == lockcount == 0 */
385 if (adf->adf_lockmax == adf->adf_lockcount) {
386 adf_lock_t *tmp = (adf_lock_t *)
387 realloc(adf->adf_lock, sizeof(adf_lock_t)*
388 (adf->adf_lockmax + ARRAY_BLOCK_SIZE));
392 adf->adf_lockmax += ARRAY_BLOCK_SIZE;
394 adflock = adf->adf_lock + adf->adf_lockcount;
397 memcpy(&adflock->lock, &lock, sizeof(lock));
398 adflock->user = fork;
400 adflock->refcount = (adf->adf_lock + oldlock)->refcount;
401 } else if ((adflock->refcount = calloc(1, sizeof(int))) == NULL) {
405 (*adflock->refcount)++;
406 adf->adf_lockcount++;
410 lock.l_type = F_UNLCK;
411 if (!adf->adf_excl) set_lock(adf->adf_fd, F_SETLK, &lock);
417 /* -------------------------
418 we are using lock as tristate variable
425 static int testlock(struct ad_fd *adf, off_t off, off_t len)
434 plock = adf->adf_lock;
435 lock.l_whence = SEEK_SET;
438 /* Do we have a lock? */
439 for (i = 0; i < adf->adf_lockcount; i++) {
440 if (OVERLAP(lock.l_start, 1, plock[i].lock.l_start, plock[i].lock.l_len))
443 /* Does another process have a lock?
445 lock.l_type = (adf->adf_flags & O_RDWR) ?F_WRLCK : F_RDLCK;
447 if (set_lock(adf->adf_fd, F_GETLK, &lock) < 0) {
448 /* is that kind of error possible ?*/
449 return (errno == EACCES || errno == EAGAIN)?1:-1;
452 if (lock.l_type == F_UNLCK) {
460 /* --------------- */
461 int ad_testlock(struct adouble *ad, int eid, const off_t off)
469 if (eid == ADEID_DFORK) {
470 adf = &ad->ad_data_fork;
471 if (ad_meta_fileno(ad) != -1) {
473 lock_offset = df2off(off);
477 if (ad_meta_fileno(ad) == -1) {
478 /* there's no resource fork. return no lock */
482 lock_offset = hf2off(off);
484 return testlock(adf, lock_offset, 1);
488 /* -------------------------
489 return if a file is open by another process.
490 Optimized for the common case:
491 - there's no locks held by another process (clients)
492 - or we already know the answer and don't need to test.
494 u_int16_t ad_openforks(struct adouble *ad, u_int16_t attrbits)
502 if (!(attrbits & (ATTRBIT_DOPEN | ATTRBIT_ROPEN))) {
504 /* XXX know the locks layout:
505 AD_FILELOCK_OPEN_WR is first
506 and use it for merging requests
508 if (ad_meta_fileno(ad) != -1) {
509 /* there's a resource fork test the four bytes for
510 * data RW/RD and fork RW/RD locks in one request
517 /* no resource fork, only data RD/RW may exist */
518 adf = &ad->ad_data_fork;
519 off = AD_FILELOCK_OPEN_WR;
522 if (!testlock(adf, off, len))
525 /* either there's a lock or we already know one
528 if (!(attrbits & ATTRBIT_DOPEN)) {
529 if (ad_meta_fileno(ad) != -1) {
534 adf = &ad->ad_data_fork;
535 off = AD_FILELOCK_OPEN_WR;
537 ret = testlock(adf, off, 2) > 0? ATTRBIT_DOPEN : 0;
540 if (!(attrbits & ATTRBIT_ROPEN)) {
541 if (ad_meta_fileno(ad) != -1) {
544 ret |= testlock(adf, off, 2) > 0? ATTRBIT_ROPEN : 0;
552 /* -------------------------
554 int ad_fcntl_tmplock(struct adouble *ad, const u_int32_t eid, const int locktype,
555 const off_t off, const off_t len, const int fork)
566 if (eid == ADEID_DFORK) {
567 adf = &ad->ad_data_fork;
570 adf = &ad->ad_resource_fork;
571 if (adf->adf_fd == -1) {
572 /* there's no resource fork. return success */
575 /* if ADLOCK_FILELOCK we want a lock from offset 0
576 * it's used when deleting a file:
577 * in open we put read locks on meta datas
578 * in delete a write locks on the whole file
579 * so if the file is open by somebody else it fails
581 if (!(type & ADLOCK_FILELOCK))
582 lock.l_start += ad_getentryoff(ad, eid);
585 if (!(adf->adf_flags & O_RDWR) && (type & ADLOCK_WR)) {
586 type = (type & ~ADLOCK_WR) | ADLOCK_RD;
589 lock.l_type = XLATE_FCNTL_LOCK(type & ADLOCK_MASK);
590 lock.l_whence = SEEK_SET;
593 /* see if it's locked by another fork. */
594 if (fork && adf_findxlock(adf, fork, ADLOCK_WR |
595 ((type & ADLOCK_WR) ? ADLOCK_RD : 0),
596 lock.l_start, lock.l_len) > -1) {
601 /* okay, we might have ranges byte-locked. we need to make sure that
602 * we restore the appropriate ranges once we're done. so, we check
603 * for overlap on an unlock and relock.
604 * XXX: in the future, all the byte locks will be sorted and contiguous.
605 * we just want to upgrade all the locks and then downgrade them
607 if (!adf->adf_excl) {
608 err = set_lock(adf->adf_fd, F_SETLK, &lock);
613 if (!err && (lock.l_type == F_UNLCK))
614 adf_relockrange(adf, adf->adf_fd, lock.l_start, len);
620 /* -------------------------
621 the fork is opened in Read Write, Deny Read, Deny Write mode
622 lock the whole file once
624 int ad_excl_lock(struct adouble *ad, const u_int32_t eid)
633 lock.l_type = F_WRLCK;
634 lock.l_whence = SEEK_SET;
637 if (eid == ADEID_DFORK) {
638 adf = &ad->ad_data_fork;
640 adf = &ad->ad_resource_fork;
641 lock.l_start = ad_getentryoff(ad, eid);
644 err = set_lock(adf->adf_fd, F_SETLK, &lock);
651 /* --------------------- */
652 void ad_fcntl_unlock(struct adouble *ad, const int fork)
656 if (ad_data_fileno(ad) != -1) {
657 adf_unlock(&ad->ad_data_fork, fork);
659 if (ad_reso_fileno(ad) != -1) {
660 adf_unlock(&ad->ad_resource_fork, fork);
663 if (ad->ad_flags != AD_VERSION_EA) {
666 if (ad_meta_fileno(ad) != -1) {
667 adf_unlock(&ad->ad_metadata_fork, fork);