return fcntl(tdb->fd, F_SETLKW, &fl);
}
+/* list -1 is the alloc list, otherwise a hash chain. */
+static tdb_off_t lock_offset(int list)
+{
+ return FREELIST_TOP + 4*list;
+}
+
/* a byte range locking function - return 0 on success
this functions locks/unlocks 1 byte at the specified offset.
return -1;
}
-/* list -1 is the alloc list, otherwise a hash chain. */
-static tdb_off_t lock_offset(int list)
-{
- return FREELIST_TOP + 4*list;
-}
-
static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
tdb_off_t offset)
{
/* Since fcntl locks don't nest, we do a lock for the first one,
and simply bump the count for future ones */
- if (tdb->methods->brlock(tdb, ltype, offset, 1, flags)) {
+ if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
return -1;
}
return 0;
}
-/* lock a list in the database. list -1 is the alloc list */
-int tdb_lock(struct tdb_context *tdb, int list, int ltype)
+static int tdb_lock_and_recover(struct tdb_context *tdb)
+{
+ int ret;
+
+ /* We need to match locking order in transaction commit. */
+ if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT)) {
+ return -1;
+ }
+
+ if (tdb_brlock(tdb, F_WRLCK, OPEN_LOCK, 1, TDB_LOCK_WAIT)) {
+ tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
+ return -1;
+ }
+
+ ret = tdb_transaction_recover(tdb);
+
+ tdb_brunlock(tdb, F_WRLCK, OPEN_LOCK, 1);
+ tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
+
+ return ret;
+}
+
+static bool have_data_locks(const struct tdb_context *tdb)
+{
+ unsigned int i;
+
+ for (i = 0; i < tdb->num_lockrecs; i++) {
+ if (tdb->lockrecs[i].off >= lock_offset(-1))
+ return true;
+ }
+ return false;
+}
+
+static int tdb_lock_list(struct tdb_context *tdb, int list, int ltype,
+ enum tdb_lock_flags waitflag)
{
int ret;
+ bool check = false;
/* a allrecord lock allows us to avoid per chain locks */
if (tdb->allrecord_lock.count &&
tdb->ecode = TDB_ERR_LOCK;
ret = -1;
} else {
- ret = tdb_nest_lock(tdb, lock_offset(list), ltype,
- TDB_LOCK_WAIT);
+ /* Only check when we grab first data lock. */
+ check = !have_data_locks(tdb);
+ ret = tdb_nest_lock(tdb, lock_offset(list), ltype, waitflag);
+
+ if (ret == 0 && check && tdb_needs_recovery(tdb)) {
+ tdb_nest_unlock(tdb, lock_offset(list), ltype, false);
+
+ if (tdb_lock_and_recover(tdb) == -1) {
+ return -1;
+ }
+ return tdb_lock_list(tdb, list, ltype, waitflag);
+ }
}
+ return ret;
+}
+
+/* lock a list in the database. list -1 is the alloc list */
+int tdb_lock(struct tdb_context *tdb, int list, int ltype)
+{
+ int ret;
+
+ ret = tdb_lock_list(tdb, list, ltype, TDB_LOCK_WAIT);
if (ret) {
TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d "
"ltype=%d (%s)\n", list, ltype, strerror(errno)));
/* lock a list in the database. list -1 is the alloc list. non-blocking lock */
int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype)
{
- /* a allrecord lock allows us to avoid per chain locks */
- if (tdb->allrecord_lock.count &&
- (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
- return 0;
- }
-
- if (tdb->allrecord_lock.count) {
- tdb->ecode = TDB_ERR_LOCK;
- return -1;
- }
-
- return tdb_nest_lock(tdb, lock_offset(list), ltype, TDB_LOCK_NOWAIT);
+ return tdb_lock_list(tdb, list, ltype, TDB_LOCK_NOWAIT);
}
if (mark_lock) {
ret = 0;
} else {
- ret = tdb->methods->brunlock(tdb, ltype, offset, 1);
+ ret = tdb_brunlock(tdb, ltype, offset, 1);
}
/*
return tdb_nest_unlock(tdb, TRANSACTION_LOCK, ltype, false);
}
-
-/* lock/unlock entire database. It can only be upgradable if you have some
- * other way of guaranteeing exclusivity (ie. transaction write lock). */
-int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
- enum tdb_lock_flags flags, bool upgradable)
+/* Returns 0 if all done, -1 if error, 1 if ok. */
+static int tdb_allrecord_check(struct tdb_context *tdb, int ltype,
+ enum tdb_lock_flags flags, bool upgradable)
{
/* There are no locks on read-only dbs */
if (tdb->read_only || tdb->traverse_read) {
tdb->ecode = TDB_ERR_LOCK;
return -1;
}
+ return 1;
+}
- if (tdb->methods->brlock(tdb, ltype, FREELIST_TOP, 0, flags)) {
- if (flags & TDB_LOCK_WAIT) {
- TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lockall failed (%s)\n", strerror(errno)));
- }
+/* We only need to lock individual bytes, but Linux merges consecutive locks
+ * so we lock in contiguous ranges. */
+static int tdb_chainlock_gradual(struct tdb_context *tdb,
+ int ltype, enum tdb_lock_flags flags,
+ size_t off, size_t len)
+{
+ int ret;
+ enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);
+
+ if (len <= 4) {
+ /* Single record. Just do blocking lock. */
+ return tdb_brlock(tdb, ltype, off, len, flags);
+ }
+
+ /* First we try non-blocking. */
+ ret = tdb_brlock(tdb, ltype, off, len, nb_flags);
+ if (ret == 0) {
+ return 0;
+ }
+
+ /* Try locking first half, then second. */
+ ret = tdb_chainlock_gradual(tdb, ltype, flags, off, len / 2);
+ if (ret == -1)
+ return -1;
+
+ ret = tdb_chainlock_gradual(tdb, ltype, flags,
+ off + len / 2, len - len / 2);
+ if (ret == -1) {
+ tdb_brunlock(tdb, ltype, off, len / 2);
+ return -1;
+ }
+ return 0;
+}
+
+/* lock/unlock entire database. It can only be upgradable if you have some
+ * other way of guaranteeing exclusivity (ie. transaction write lock).
+ * We do the locking gradually to avoid being starved by smaller locks. */
+int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
+ enum tdb_lock_flags flags, bool upgradable)
+{
+ switch (tdb_allrecord_check(tdb, ltype, flags, upgradable)) {
+ case -1:
+ return -1;
+ case 0:
+ return 0;
+ }
+
+ /* We cover two kinds of locks:
+ * 1) Normal chain locks. Taken for almost all operations.
+ * 3) Individual records locks. Taken after normal or free
+ * chain locks.
+ *
+ * It is (1) which cause the starvation problem, so we're only
+ * gradual for that. */
+ if (tdb_chainlock_gradual(tdb, ltype, flags, FREELIST_TOP,
+ tdb->header.hash_size * 4) == -1) {
+ return -1;
+ }
+
+ /* Grab individual record locks. */
+ if (tdb_brlock(tdb, ltype, lock_offset(tdb->header.hash_size), 0,
+ flags) == -1) {
+ tdb_brunlock(tdb, ltype, FREELIST_TOP,
+ tdb->header.hash_size * 4);
return -1;
}
tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
tdb->allrecord_lock.off = upgradable;
+ if (tdb_needs_recovery(tdb)) {
+ bool mark = flags & TDB_LOCK_MARK_ONLY;
+ tdb_allrecord_unlock(tdb, ltype, mark);
+ if (mark) {
+ tdb->ecode = TDB_ERR_LOCK;
+ TDB_LOG((tdb, TDB_DEBUG_ERROR,
+ "tdb_lockall_mark cannot do recovery\n"));
+ return -1;
+ }
+ if (tdb_lock_and_recover(tdb) == -1) {
+ return -1;
+ }
+ return tdb_allrecord_lock(tdb, ltype, flags, upgradable);
+ }
+
return 0;
}
return 0;
}
- if (!mark_lock &&
- tdb->methods->brunlock(tdb, ltype, FREELIST_TOP, 0)) {
+ if (!mark_lock && tdb_brunlock(tdb, ltype, FREELIST_TOP, 0)) {
TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed (%s)\n", strerror(errno)));
return -1;
}
if (tdb->allrecord_lock.count) {
return 0;
}
- return off ? tdb->methods->brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 0;
+ return off ? tdb_brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 0;
}
/*
for (i = &tdb->travlocks; i; i = i->next)
if (i->off == off)
return -1;
- return tdb->methods->brlock(tdb, F_WRLCK, off, 1, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE);
+ if (tdb->allrecord_lock.count) {
+ if (tdb->allrecord_lock.ltype == F_WRLCK) {
+ return 0;
+ }
+ return -1;
+ }
+ return tdb_brlock(tdb, F_WRLCK, off, 1, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE);
}
int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
{
- return tdb->methods->brunlock(tdb, F_WRLCK, off, 1);
+ if (tdb->allrecord_lock.count) {
+ return 0;
+ }
+ return tdb_brunlock(tdb, F_WRLCK, off, 1);
}
/* fcntl locks don't stack: avoid unlocking someone else's */
for (i = &tdb->travlocks; i; i = i->next)
if (i->off == off)
count++;
- return (count == 1 ? tdb->methods->brunlock(tdb, F_RDLCK, off, 1) : 0);
+ return (count == 1 ? tdb_brunlock(tdb, F_RDLCK, off, 1) : 0);
}
bool tdb_have_extra_locks(struct tdb_context *tdb)
projects / ccan / blobdiff