[GFS2] Fix ordering bug in lock_dlm

This looks like a lot of change, but in fact its not. Mostly its
things moving from one file to another. The change is just that
instead of queuing lock completions and callbacks from the DLM
we now pass them directly to GFS2.

This gives us a net loss of two list heads per glock (a fair
saving in memory) plus a reduction in the latency of delivering
the messages to GFS2, plus we now have one thread fewer as well.
There was a bug where callbacks and completions could be delivered
in the wrong order due to this unnecessary queuing which is fixed
by this patch.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Bob Peterson <rpeterso@redhat.com>

1 files changed, 287 insertions, 66 deletions

diff --git a/fs/gfs2/locking/dlm/lock.c b/fs/gfs2/locking/dlm/lock.c
index fed9a67be0f..871ffc9578f 100644
--- a/fs/gfs2/locking/dlm/lock.c
+++ b/fs/gfs2/locking/dlm/lock.c
@@ -11,46 +11,63 @@
 
 static char junk_lvb[GDLM_LVB_SIZE];
 
-static void queue_complete(struct gdlm_lock *lp)
+
+/* convert dlm lock-mode to gfs lock-state */
+
+static s16 gdlm_make_lmstate(s16 dlmmode)
 {
-	struct gdlm_ls *ls = lp->ls;
+	switch (dlmmode) {
+	case DLM_LOCK_IV:
+	case DLM_LOCK_NL:
+		return LM_ST_UNLOCKED;
+	case DLM_LOCK_EX:
+		return LM_ST_EXCLUSIVE;
+	case DLM_LOCK_CW:
+		return LM_ST_DEFERRED;
+	case DLM_LOCK_PR:
+		return LM_ST_SHARED;
+	}
+	gdlm_assert(0, "unknown DLM mode %d", dlmmode);
+	return -1;
+}
 
-	clear_bit(LFL_ACTIVE, &lp->flags);
+/* A lock placed on this queue is re-submitted to DLM as soon as the lock_dlm
+   thread gets to it. */
+
+static void queue_submit(struct gdlm_lock *lp)
+{
+	struct gdlm_ls *ls = lp->ls;
 
 	spin_lock(&ls->async_lock);
-	list_add_tail(&lp->clist, &ls->complete);
+	list_add_tail(&lp->delay_list, &ls->submit);
 	spin_unlock(&ls->async_lock);
 	wake_up(&ls->thread_wait);
 }
 
-static inline void gdlm_ast(void *astarg)
+static void wake_up_ast(struct gdlm_lock *lp)
 {
-	queue_complete(astarg);
+	clear_bit(LFL_AST_WAIT, &lp->flags);
+	smp_mb__after_clear_bit();
+	wake_up_bit(&lp->flags, LFL_AST_WAIT);
 }
 
-static inline void gdlm_bast(void *astarg, int mode)
+static void gdlm_delete_lp(struct gdlm_lock *lp)
 {
-	struct gdlm_lock *lp = astarg;
 	struct gdlm_ls *ls = lp->ls;
 
-	if (!mode) {
-		printk(KERN_INFO "lock_dlm: bast mode zero %x,%llx\n",
-			lp->lockname.ln_type,
-			(unsigned long long)lp->lockname.ln_number);
-		return;
-	}
-
 	spin_lock(&ls->async_lock);
-	if (!lp->bast_mode) {
-		list_add_tail(&lp->blist, &ls->blocking);
-		lp->bast_mode = mode;
-	} else if (lp->bast_mode < mode)
-		lp->bast_mode = mode;
+	if (!list_empty(&lp->delay_list))
+		list_del_init(&lp->delay_list);
+	gdlm_assert(!list_empty(&lp->all_list), "%x,%llx", lp->lockname.ln_type,
+		    (unsigned long long)lp->lockname.ln_number);
+	list_del_init(&lp->all_list);
+	ls->all_locks_count--;
 	spin_unlock(&ls->async_lock);
-	wake_up(&ls->thread_wait);
+
+	kfree(lp);
 }
 
-void gdlm_queue_delayed(struct gdlm_lock *lp)
+static void gdlm_queue_delayed(struct gdlm_lock *lp)
 {
 	struct gdlm_ls *ls = lp->ls;
 
@@ -59,6 +76,249 @@ void gdlm_queue_delayed(struct gdlm_lock *lp)
 	spin_unlock(&ls->async_lock);
 }
 
+static void process_complete(struct gdlm_lock *lp)
+{
+	struct gdlm_ls *ls = lp->ls;
+	struct lm_async_cb acb;
+	s16 prev_mode = lp->cur;
+
+	memset(&acb, 0, sizeof(acb));
+
+	if (lp->lksb.sb_status == -DLM_ECANCEL) {
+		log_info("complete dlm cancel %x,%llx flags %lx",
+		 	 lp->lockname.ln_type,
+			 (unsigned long long)lp->lockname.ln_number,
+			 lp->flags);
+
+		lp->req = lp->cur;
+		acb.lc_ret |= LM_OUT_CANCELED;
+		if (lp->cur == DLM_LOCK_IV)
+			lp->lksb.sb_lkid = 0;
+		goto out;
+	}
+
+	if (test_and_clear_bit(LFL_DLM_UNLOCK, &lp->flags)) {
+		if (lp->lksb.sb_status != -DLM_EUNLOCK) {
+			log_info("unlock sb_status %d %x,%llx flags %lx",
+				 lp->lksb.sb_status, lp->lockname.ln_type,
+				 (unsigned long long)lp->lockname.ln_number,
+				 lp->flags);
+			return;
+		}
+
+		lp->cur = DLM_LOCK_IV;
+		lp->req = DLM_LOCK_IV;
+		lp->lksb.sb_lkid = 0;
+
+		if (test_and_clear_bit(LFL_UNLOCK_DELETE, &lp->flags)) {
+			gdlm_delete_lp(lp);
+			return;
+		}
+		goto out;
+	}
+
+	if (lp->lksb.sb_flags & DLM_SBF_VALNOTVALID)
+		memset(lp->lksb.sb_lvbptr, 0, GDLM_LVB_SIZE);
+
+	if (lp->lksb.sb_flags & DLM_SBF_ALTMODE) {
+		if (lp->req == DLM_LOCK_PR)
+			lp->req = DLM_LOCK_CW;
+		else if (lp->req == DLM_LOCK_CW)
+			lp->req = DLM_LOCK_PR;
+	}
+
+	/*
+	 * A canceled lock request.  The lock was just taken off the delayed
+	 * list and was never even submitted to dlm.
+	 */
+
+	if (test_and_clear_bit(LFL_CANCEL, &lp->flags)) {
+		log_info("complete internal cancel %x,%llx",
+		 	 lp->lockname.ln_type,
+			 (unsigned long long)lp->lockname.ln_number);
+		lp->req = lp->cur;
+		acb.lc_ret |= LM_OUT_CANCELED;
+		goto out;
+	}
+
+	/*
+	 * An error occured.
+	 */
+
+	if (lp->lksb.sb_status) {
+		/* a "normal" error */
+		if ((lp->lksb.sb_status == -EAGAIN) &&
+		    (lp->lkf & DLM_LKF_NOQUEUE)) {
+			lp->req = lp->cur;
+			if (lp->cur == DLM_LOCK_IV)
+				lp->lksb.sb_lkid = 0;
+			goto out;
+		}
+
+		/* this could only happen with cancels I think */
+		log_info("ast sb_status %d %x,%llx flags %lx",
+			 lp->lksb.sb_status, lp->lockname.ln_type,
+			 (unsigned long long)lp->lockname.ln_number,
+			 lp->flags);
+		if (lp->lksb.sb_status == -EDEADLOCK &&
+		    lp->ls->fsflags & LM_MFLAG_CONV_NODROP) {
+			lp->req = lp->cur;
+			acb.lc_ret |= LM_OUT_CONV_DEADLK;
+			if (lp->cur == DLM_LOCK_IV)
+				lp->lksb.sb_lkid = 0;
+			goto out;
+		} else
+			return;
+	}
+
+	/*
+	 * This is an AST for an EX->EX conversion for sync_lvb from GFS.
+	 */
+
+	if (test_and_clear_bit(LFL_SYNC_LVB, &lp->flags)) {
+		wake_up_ast(lp);
+		return;
+	}
+
+	/*
+	 * A lock has been demoted to NL because it initially completed during
+	 * BLOCK_LOCKS.  Now it must be requested in the originally requested
+	 * mode.
+	 */
+
+	if (test_and_clear_bit(LFL_REREQUEST, &lp->flags)) {
+		gdlm_assert(lp->req == DLM_LOCK_NL, "%x,%llx",
+			    lp->lockname.ln_type,
+			    (unsigned long long)lp->lockname.ln_number);
+		gdlm_assert(lp->prev_req > DLM_LOCK_NL, "%x,%llx",
+			    lp->lockname.ln_type,
+			    (unsigned long long)lp->lockname.ln_number);
+
+		lp->cur = DLM_LOCK_NL;
+		lp->req = lp->prev_req;
+		lp->prev_req = DLM_LOCK_IV;
+		lp->lkf &= ~DLM_LKF_CONVDEADLK;
+
+		set_bit(LFL_NOCACHE, &lp->flags);
+
+		if (test_bit(DFL_BLOCK_LOCKS, &ls->flags) &&
+		    !test_bit(LFL_NOBLOCK, &lp->flags))
+			gdlm_queue_delayed(lp);
+		else
+			queue_submit(lp);
+		return;
+	}
+
+	/*
+	 * A request is granted during dlm recovery.  It may be granted
+	 * because the locks of a failed node were cleared.  In that case,
+	 * there may be inconsistent data beneath this lock and we must wait
+	 * for recovery to complete to use it.  When gfs recovery is done this
+	 * granted lock will be converted to NL and then reacquired in this
+	 * granted state.
+	 */
+
+	if (test_bit(DFL_BLOCK_LOCKS, &ls->flags) &&
+	    !test_bit(LFL_NOBLOCK, &lp->flags) &&
+	    lp->req != DLM_LOCK_NL) {
+
+		lp->cur = lp->req;
+		lp->prev_req = lp->req;
+		lp->req = DLM_LOCK_NL;
+		lp->lkf |= DLM_LKF_CONVERT;
+		lp->lkf &= ~DLM_LKF_CONVDEADLK;
+
+		log_debug("rereq %x,%llx id %x %d,%d",
+			  lp->lockname.ln_type,
+			  (unsigned long long)lp->lockname.ln_number,
+			  lp->lksb.sb_lkid, lp->cur, lp->req);
+
+		set_bit(LFL_REREQUEST, &lp->flags);
+		queue_submit(lp);
+		return;
+	}
+
+	/*
+	 * DLM demoted the lock to NL before it was granted so GFS must be
+	 * told it cannot cache data for this lock.
+	 */
+
+	if (lp->lksb.sb_flags & DLM_SBF_DEMOTED)
+		set_bit(LFL_NOCACHE, &lp->flags);
+
+out:
+	/*
+	 * This is an internal lock_dlm lock
+	 */
+
+	if (test_bit(LFL_INLOCK, &lp->flags)) {
+		clear_bit(LFL_NOBLOCK, &lp->flags);
+		lp->cur = lp->req;
+		wake_up_ast(lp);
+		return;
+	}
+
+	/*
+	 * Normal completion of a lock request.  Tell GFS it now has the lock.
+	 */
+
+	clear_bit(LFL_NOBLOCK, &lp->flags);
+	lp->cur = lp->req;
+
+	acb.lc_name = lp->lockname;
+	acb.lc_ret |= gdlm_make_lmstate(lp->cur);
+
+	if (!test_and_clear_bit(LFL_NOCACHE, &lp->flags) &&
+	    (lp->cur > DLM_LOCK_NL) && (prev_mode > DLM_LOCK_NL))
+		acb.lc_ret |= LM_OUT_CACHEABLE;
+
+	ls->fscb(ls->sdp, LM_CB_ASYNC, &acb);
+}
+
+static void gdlm_ast(void *astarg)
+{
+	struct gdlm_lock *lp = astarg;
+	clear_bit(LFL_ACTIVE, &lp->flags);
+	process_complete(lp);
+}
+
+static void process_blocking(struct gdlm_lock *lp, int bast_mode)
+{
+	struct gdlm_ls *ls = lp->ls;
+	unsigned int cb = 0;
+
+	switch (gdlm_make_lmstate(bast_mode)) {
+	case LM_ST_EXCLUSIVE:
+		cb = LM_CB_NEED_E;
+		break;
+	case LM_ST_DEFERRED:
+		cb = LM_CB_NEED_D;
+		break;
+	case LM_ST_SHARED:
+		cb = LM_CB_NEED_S;
+		break;
+	default:
+		gdlm_assert(0, "unknown bast mode %u", bast_mode);
+	}
+
+	ls->fscb(ls->sdp, cb, &lp->lockname);
+}
+
+
+static void gdlm_bast(void *astarg, int mode)
+{
+	struct gdlm_lock *lp = astarg;
+
+	if (!mode) {
+		printk(KERN_INFO "lock_dlm: bast mode zero %x,%llx\n",
+			lp->lockname.ln_type,
+			(unsigned long long)lp->lockname.ln_number);
+		return;
+	}
+
+	process_blocking(lp, mode);
+}
+
 /* convert gfs lock-state to dlm lock-mode */
 
 static s16 make_mode(s16 lmstate)
@@ -77,24 +337,6 @@ static s16 make_mode(s16 lmstate)
 	return -1;
 }
 
-/* convert dlm lock-mode to gfs lock-state */
-
-s16 gdlm_make_lmstate(s16 dlmmode)
-{
-	switch (dlmmode) {
-	case DLM_LOCK_IV:
-	case DLM_LOCK_NL:
-		return LM_ST_UNLOCKED;
-	case DLM_LOCK_EX:
-		return LM_ST_EXCLUSIVE;
-	case DLM_LOCK_CW:
-		return LM_ST_DEFERRED;
-	case DLM_LOCK_PR:
-		return LM_ST_SHARED;
-	}
-	gdlm_assert(0, "unknown DLM mode %d", dlmmode);
-	return -1;
-}
 
 /* verify agreement with GFS on the current lock state, NB: DLM_LOCK_NL and
    DLM_LOCK_IV are both considered LM_ST_UNLOCKED by GFS. */
@@ -173,10 +415,6 @@ static int gdlm_create_lp(struct gdlm_ls *ls, struct lm_lockname *name,
 	make_strname(name, &lp->strname);
 	lp->ls = ls;
 	lp->cur = DLM_LOCK_IV;
-	lp->lvb = NULL;
-	lp->hold_null = NULL;
-	INIT_LIST_HEAD(&lp->clist);
-	INIT_LIST_HEAD(&lp->blist);
 	INIT_LIST_HEAD(&lp->delay_list);
 
 	spin_lock(&ls->async_lock);
@@ -188,26 +426,6 @@ static int gdlm_create_lp(struct gdlm_ls *ls, struct lm_lockname *name,
 	return 0;
 }
 
-void gdlm_delete_lp(struct gdlm_lock *lp)
-{
-	struct gdlm_ls *ls = lp->ls;
-
-	spin_lock(&ls->async_lock);
-	if (!list_empty(&lp->clist))
-		list_del_init(&lp->clist);
-	if (!list_empty(&lp->blist))
-		list_del_init(&lp->blist);
-	if (!list_empty(&lp->delay_list))
-		list_del_init(&lp->delay_list);
-	gdlm_assert(!list_empty(&lp->all_list), "%x,%llx", lp->lockname.ln_type,
-		    (unsigned long long)lp->lockname.ln_number);
-	list_del_init(&lp->all_list);
-	ls->all_locks_count--;
-	spin_unlock(&ls->async_lock);
-
-	kfree(lp);
-}
-
 int gdlm_get_lock(void *lockspace, struct lm_lockname *name,
 		  void **lockp)
 {
@@ -261,7 +479,7 @@ unsigned int gdlm_do_lock(struct gdlm_lock *lp)
 
 	if ((error == -EAGAIN) && (lp->lkf & DLM_LKF_NOQUEUE)) {
 		lp->lksb.sb_status = -EAGAIN;
-		queue_complete(lp);
+		gdlm_ast(lp);
 		error = 0;
 	}
 
@@ -311,6 +529,9 @@ unsigned int gdlm_lock(void *lock, unsigned int cur_state,
 	if (req_state == LM_ST_UNLOCKED)
 		return gdlm_unlock(lock, cur_state);
 
+	if (req_state == LM_ST_UNLOCKED)
+		return gdlm_unlock(lock, cur_state);
+
 	clear_bit(LFL_DLM_CANCEL, &lp->flags);
 	if (flags & LM_FLAG_NOEXP)
 		set_bit(LFL_NOBLOCK, &lp->flags);
@@ -354,7 +575,7 @@ void gdlm_cancel(void *lock)
 	if (delay_list) {
 		set_bit(LFL_CANCEL, &lp->flags);
 		set_bit(LFL_ACTIVE, &lp->flags);
-		queue_complete(lp);
+		gdlm_ast(lp);
 		return;
 	}