struct buffer_head **bh);
static void ocfs2_drop_osb_locks(struct ocfs2_super *osb);
static inline int ocfs2_highest_compat_lock_level(int level);
-static void ocfs2_prepare_downconvert(struct ocfs2_lock_res *lockres,
- int new_level);
+static unsigned int ocfs2_prepare_downconvert(struct ocfs2_lock_res *lockres,
+ int new_level);
static int ocfs2_downconvert_lock(struct ocfs2_super *osb,
struct ocfs2_lock_res *lockres,
int new_level,
- int lvb);
+ int lvb,
+ unsigned int generation);
static int ocfs2_prepare_cancel_convert(struct ocfs2_super *osb,
struct ocfs2_lock_res *lockres);
static int ocfs2_cancel_convert(struct ocfs2_super *osb,
return needs_downconvert;
}
+/*
+ * OCFS2_LOCK_PENDING and l_pending_gen.
+ *
+ * Why does OCFS2_LOCK_PENDING exist? To close a race between setting
+ * OCFS2_LOCK_BUSY and calling ocfs2_dlm_lock(). See ocfs2_unblock_lock()
+ * for more details on the race.
+ *
+ * OCFS2_LOCK_PENDING closes the race quite nicely. However, it introduces
+ * a race on itself. In o2dlm, we can get the ast before ocfs2_dlm_lock()
+ * returns. The ast clears OCFS2_LOCK_BUSY, and must therefore clear
+ * OCFS2_LOCK_PENDING at the same time. When ocfs2_dlm_lock() returns,
+ * the caller is going to try to clear PENDING again. If nothing else is
+ * happening, __lockres_clear_pending() sees PENDING is unset and does
+ * nothing.
+ *
+ * But what if another path (eg downconvert thread) has just started a
+ * new locking action? The other path has re-set PENDING. Our path
+ * cannot clear PENDING, because that will re-open the original race
+ * window.
+ *
+ * [Example]
+ *
+ * ocfs2_meta_lock()
+ * ocfs2_cluster_lock()
+ * set BUSY
+ * set PENDING
+ * drop l_lock
+ * ocfs2_dlm_lock()
+ * ocfs2_locking_ast() ocfs2_downconvert_thread()
+ * clear PENDING ocfs2_unblock_lock()
+ * take_l_lock
+ * !BUSY
+ * ocfs2_prepare_downconvert()
+ * set BUSY
+ * set PENDING
+ * drop l_lock
+ * take l_lock
+ * clear PENDING
+ * drop l_lock
+ * <window>
+ * ocfs2_dlm_lock()
+ *
+ * So as you can see, we now have a window where l_lock is not held,
+ * PENDING is not set, and ocfs2_dlm_lock() has not been called.
+ *
+ * The core problem is that ocfs2_cluster_lock() has cleared the PENDING
+ * set by ocfs2_prepare_downconvert(). That wasn't nice.
+ *
+ * To solve this we introduce l_pending_gen. A call to
+ * lockres_clear_pending() will only do so when it is passed a generation
+ * number that matches the lockres. lockres_set_pending() will return the
+ * current generation number. When ocfs2_cluster_lock() goes to clear
+ * PENDING, it passes the generation it got from set_pending(). In our
+ * example above, the generation numbers will *not* match. Thus,
+ * ocfs2_cluster_lock() will not clear the PENDING set by
+ * ocfs2_prepare_downconvert().
+ */
+
+/* Unlocked version for ocfs2_locking_ast() */
+static void __lockres_clear_pending(struct ocfs2_lock_res *lockres,
+ unsigned int generation,
+ struct ocfs2_super *osb)
+{
+ assert_spin_locked(&lockres->l_lock);
+
+ /*
+ * The ast and locking functions can race us here. The winner
+ * will clear pending, the loser will not.
+ */
+ if (!(lockres->l_flags & OCFS2_LOCK_PENDING) ||
+ (lockres->l_pending_gen != generation))
+ return;
+
+ lockres_clear_flags(lockres, OCFS2_LOCK_PENDING);
+ lockres->l_pending_gen++;
+
+ /*
+ * The downconvert thread may have skipped us because we
+ * were PENDING. Wake it up.
+ */
+ if (lockres->l_flags & OCFS2_LOCK_BLOCKED)
+ ocfs2_wake_downconvert_thread(osb);
+}
+
+/* Locked version for callers of ocfs2_dlm_lock() */
+static void lockres_clear_pending(struct ocfs2_lock_res *lockres,
+ unsigned int generation,
+ struct ocfs2_super *osb)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&lockres->l_lock, flags);
+ __lockres_clear_pending(lockres, generation, osb);
+ spin_unlock_irqrestore(&lockres->l_lock, flags);
+}
+
+static unsigned int lockres_set_pending(struct ocfs2_lock_res *lockres)
+{
+ assert_spin_locked(&lockres->l_lock);
+ BUG_ON(!(lockres->l_flags & OCFS2_LOCK_BUSY));
+
+ lockres_or_flags(lockres, OCFS2_LOCK_PENDING);
+
+ return lockres->l_pending_gen;
+}
+
+
static void ocfs2_blocking_ast(void *opaque, int level)
{
struct ocfs2_lock_res *lockres = opaque;
static void ocfs2_locking_ast(void *opaque)
{
struct ocfs2_lock_res *lockres = opaque;
+ struct ocfs2_super *osb = ocfs2_get_lockres_osb(lockres);
unsigned long flags;
+ int status;
spin_lock_irqsave(&lockres->l_lock, flags);
- if (ocfs2_dlm_lock_status(&lockres->l_lksb)) {
+ status = ocfs2_dlm_lock_status(&lockres->l_lksb);
+
+ if (status == -EAGAIN) {
+ lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
+ goto out;
+ }
+
+ if (status) {
mlog(ML_ERROR, "lockres %s: lksb status value of %d!\n",
- lockres->l_name,
- ocfs2_dlm_lock_status(&lockres->l_lksb));
+ lockres->l_name, status);
spin_unlock_irqrestore(&lockres->l_lock, flags);
return;
}
lockres->l_unlock_action);
BUG();
}
-
+out:
/* set it to something invalid so if we get called again we
* can catch it. */
lockres->l_action = OCFS2_AST_INVALID;
+ /* Did we try to cancel this lock? Clear that state */
+ if (lockres->l_unlock_action == OCFS2_UNLOCK_CANCEL_CONVERT)
+ lockres->l_unlock_action = OCFS2_UNLOCK_INVALID;
+
+ /*
+ * We may have beaten the locking functions here. We certainly
+ * know that dlm_lock() has been called :-)
+ * Because we can't have two lock calls in flight at once, we
+ * can use lockres->l_pending_gen.
+ */
+ __lockres_clear_pending(lockres, lockres->l_pending_gen, osb);
+
wake_up(&lockres->l_event);
spin_unlock_irqrestore(&lockres->l_lock, flags);
}
{
int ret = 0;
unsigned long flags;
+ unsigned int gen;
mlog_entry_void();
lockres->l_action = OCFS2_AST_ATTACH;
lockres->l_requested = level;
lockres_or_flags(lockres, OCFS2_LOCK_BUSY);
+ gen = lockres_set_pending(lockres);
spin_unlock_irqrestore(&lockres->l_lock, flags);
ret = ocfs2_dlm_lock(osb->cconn,
lockres->l_name,
OCFS2_LOCK_ID_MAX_LEN - 1,
lockres);
+ lockres_clear_pending(lockres, gen, osb);
if (ret) {
ocfs2_log_dlm_error("ocfs2_dlm_lock", ret, lockres);
ocfs2_recover_from_dlm_error(lockres, 1);
int wait, catch_signals = !(osb->s_mount_opt & OCFS2_MOUNT_NOINTR);
int ret = 0; /* gcc doesn't realize wait = 1 guarantees ret is set */
unsigned long flags;
+ unsigned int gen;
+ int noqueue_attempted = 0;
mlog_entry_void();
}
if (level > lockres->l_level) {
+ if (noqueue_attempted > 0) {
+ ret = -EAGAIN;
+ goto unlock;
+ }
+ if (lkm_flags & DLM_LKF_NOQUEUE)
+ noqueue_attempted = 1;
+
if (lockres->l_action != OCFS2_AST_INVALID)
mlog(ML_ERROR, "lockres %s has action %u pending\n",
lockres->l_name, lockres->l_action);
lockres->l_requested = level;
lockres_or_flags(lockres, OCFS2_LOCK_BUSY);
+ gen = lockres_set_pending(lockres);
spin_unlock_irqrestore(&lockres->l_lock, flags);
BUG_ON(level == DLM_LOCK_IV);
lockres->l_name,
OCFS2_LOCK_ID_MAX_LEN - 1,
lockres);
+ lockres_clear_pending(lockres, gen, osb);
if (ret) {
if (!(lkm_flags & DLM_LKF_NOQUEUE) ||
(ret != -EAGAIN)) {
*/
int ocfs2_file_lock(struct file *file, int ex, int trylock)
{
- int ret, level = ex ? LKM_EXMODE : LKM_PRMODE;
- unsigned int lkm_flags = trylock ? LKM_NOQUEUE : 0;
+ int ret, level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
+ unsigned int lkm_flags = trylock ? DLM_LKF_NOQUEUE : 0;
unsigned long flags;
struct ocfs2_file_private *fp = file->private_data;
struct ocfs2_lock_res *lockres = &fp->fp_flock;
* Get the lock at NLMODE to start - that way we
* can cancel the upconvert request if need be.
*/
- ret = ocfs2_lock_create(osb, lockres, LKM_NLMODE, 0);
+ ret = ocfs2_lock_create(osb, lockres, DLM_LOCK_NL, 0);
if (ret < 0) {
mlog_errno(ret);
goto out;
}
lockres->l_action = OCFS2_AST_CONVERT;
- lkm_flags |= LKM_CONVERT;
+ lkm_flags |= DLM_LKF_CONVERT;
lockres->l_requested = level;
lockres_or_flags(lockres, OCFS2_LOCK_BUSY);
* to just bubble sucess back up to the user.
*/
ret = ocfs2_flock_handle_signal(lockres, level);
+ } else if (!ret && (level > lockres->l_level)) {
+ /* Trylock failed asynchronously */
+ BUG_ON(!trylock);
+ ret = -EAGAIN;
}
out:
void ocfs2_file_unlock(struct file *file)
{
int ret;
+ unsigned int gen;
unsigned long flags;
struct ocfs2_file_private *fp = file->private_data;
struct ocfs2_lock_res *lockres = &fp->fp_flock;
if (!(lockres->l_flags & OCFS2_LOCK_ATTACHED))
return;
- if (lockres->l_level == LKM_NLMODE)
+ if (lockres->l_level == DLM_LOCK_NL)
return;
mlog(0, "Unlock: \"%s\" flags: 0x%lx, level: %d, act: %d\n",
lockres_or_flags(lockres, OCFS2_LOCK_BLOCKED);
lockres->l_blocking = DLM_LOCK_EX;
- ocfs2_prepare_downconvert(lockres, LKM_NLMODE);
+ gen = ocfs2_prepare_downconvert(lockres, DLM_LOCK_NL);
lockres_add_mask_waiter(lockres, &mw, OCFS2_LOCK_BUSY, 0);
spin_unlock_irqrestore(&lockres->l_lock, flags);
- ret = ocfs2_downconvert_lock(osb, lockres, LKM_NLMODE, 0);
+ ret = ocfs2_downconvert_lock(osb, lockres, DLM_LOCK_NL, 0, gen);
if (ret) {
mlog_errno(ret);
return;
}
/* for now, uuid == domain */
- status = ocfs2_cluster_connect(osb->uuid_str,
+ status = ocfs2_cluster_connect(osb->osb_cluster_stack,
+ osb->uuid_str,
strlen(osb->uuid_str),
ocfs2_do_node_down, osb,
&conn);
mlog_errno(status);
mlog(ML_ERROR,
"could not find this host's node number\n");
- ocfs2_cluster_disconnect(conn);
+ ocfs2_cluster_disconnect(conn, 0);
goto bail;
}
return status;
}
-void ocfs2_dlm_shutdown(struct ocfs2_super *osb)
+void ocfs2_dlm_shutdown(struct ocfs2_super *osb,
+ int hangup_pending)
{
mlog_entry_void();
ocfs2_lock_res_free(&osb->osb_super_lockres);
ocfs2_lock_res_free(&osb->osb_rename_lockres);
- ocfs2_cluster_disconnect(osb->cconn);
+ ocfs2_cluster_disconnect(osb->cconn, hangup_pending);
osb->cconn = NULL;
ocfs2_dlm_shutdown_debug(osb);
lockres->l_unlock_action);
spin_lock_irqsave(&lockres->l_lock, flags);
- /* We tried to cancel a convert request, but it was already
- * granted. All we want to do here is clear our unlock
- * state. The wake_up call done at the bottom is redundant
- * (ocfs2_prepare_cancel_convert doesn't sleep on this) but doesn't
- * hurt anything anyway */
- if (error == -DLM_ECANCEL &&
- lockres->l_unlock_action == OCFS2_UNLOCK_CANCEL_CONVERT) {
- mlog(0, "Got cancelgrant for %s\n", lockres->l_name);
-
- /* We don't clear the busy flag in this case as it
- * should have been cleared by the ast which the dlm
- * has called. */
- goto complete_unlock;
- }
-
- /* DLM_EUNLOCK is the success code for unlock */
- if (error != -DLM_EUNLOCK) {
+ if (error) {
mlog(ML_ERROR, "Dlm passes error %d for lock %s, "
"unlock_action %d\n", error, lockres->l_name,
lockres->l_unlock_action);
}
lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
-complete_unlock:
lockres->l_unlock_action = OCFS2_UNLOCK_INVALID;
spin_unlock_irqrestore(&lockres->l_lock, flags);
if (ret) {
ocfs2_log_dlm_error("ocfs2_dlm_unlock", ret, lockres);
mlog(ML_ERROR, "lockres flags: %lu\n", lockres->l_flags);
- /* XXX Need to abstract this */
- dlm_print_one_lock(lockres->l_lksb.lksb_o2dlm.lockid);
+ ocfs2_dlm_dump_lksb(&lockres->l_lksb);
BUG();
}
mlog(0, "lock %s, successfull return from ocfs2_dlm_unlock\n",
return status;
}
-static void ocfs2_prepare_downconvert(struct ocfs2_lock_res *lockres,
- int new_level)
+static unsigned int ocfs2_prepare_downconvert(struct ocfs2_lock_res *lockres,
+ int new_level)
{
assert_spin_locked(&lockres->l_lock);
lockres->l_action = OCFS2_AST_DOWNCONVERT;
lockres->l_requested = new_level;
lockres_or_flags(lockres, OCFS2_LOCK_BUSY);
+ return lockres_set_pending(lockres);
}
static int ocfs2_downconvert_lock(struct ocfs2_super *osb,
struct ocfs2_lock_res *lockres,
int new_level,
- int lvb)
+ int lvb,
+ unsigned int generation)
{
int ret;
u32 dlm_flags = DLM_LKF_CONVERT;
lockres->l_name,
OCFS2_LOCK_ID_MAX_LEN - 1,
lockres);
+ lockres_clear_pending(lockres, generation, osb);
if (ret) {
ocfs2_log_dlm_error("ocfs2_dlm_lock", ret, lockres);
ocfs2_recover_from_dlm_error(lockres, 1);
int new_level;
int ret = 0;
int set_lvb = 0;
+ unsigned int gen;
mlog_entry_void();
recheck:
if (lockres->l_flags & OCFS2_LOCK_BUSY) {
+ /* XXX
+ * This is a *big* race. The OCFS2_LOCK_PENDING flag
+ * exists entirely for one reason - another thread has set
+ * OCFS2_LOCK_BUSY, but has *NOT* yet called dlm_lock().
+ *
+ * If we do ocfs2_cancel_convert() before the other thread
+ * calls dlm_lock(), our cancel will do nothing. We will
+ * get no ast, and we will have no way of knowing the
+ * cancel failed. Meanwhile, the other thread will call
+ * into dlm_lock() and wait...forever.
+ *
+ * Why forever? Because another node has asked for the
+ * lock first; that's why we're here in unblock_lock().
+ *
+ * The solution is OCFS2_LOCK_PENDING. When PENDING is
+ * set, we just requeue the unblock. Only when the other
+ * thread has called dlm_lock() and cleared PENDING will
+ * we then cancel their request.
+ *
+ * All callers of dlm_lock() must set OCFS2_DLM_PENDING
+ * at the same time they set OCFS2_DLM_BUSY. They must
+ * clear OCFS2_DLM_PENDING after dlm_lock() returns.
+ */
+ if (lockres->l_flags & OCFS2_LOCK_PENDING)
+ goto leave_requeue;
+
ctl->requeue = 1;
ret = ocfs2_prepare_cancel_convert(osb, lockres);
spin_unlock_irqrestore(&lockres->l_lock, flags);
lockres->l_ops->set_lvb(lockres);
}
- ocfs2_prepare_downconvert(lockres, new_level);
+ gen = ocfs2_prepare_downconvert(lockres, new_level);
spin_unlock_irqrestore(&lockres->l_lock, flags);
- ret = ocfs2_downconvert_lock(osb, lockres, new_level, set_lvb);
+ ret = ocfs2_downconvert_lock(osb, lockres, new_level, set_lvb,
+ gen);
+
leave:
mlog_exit(ret);
return ret;
.lp_unlock_ast = ocfs2_unlock_ast,
};
-/* This interface isn't the final one, hence the less-than-perfect names */
-void dlmglue_init_stack(void)
+void ocfs2_set_locking_protocol(void)
{
- o2cb_get_stack(&lproto);
+ ocfs2_stack_glue_set_locking_protocol(&lproto);
}
-void dlmglue_exit_stack(void)
-{
- o2cb_put_stack();
-}
static void ocfs2_process_blocked_lock(struct ocfs2_super *osb,
struct ocfs2_lock_res *lockres)