[RFC dlm/next 11/11] dlm: return void for _request_lock function

[Alexander Aring <aahringo@redhat.com>]

Change the _request_lock() function that it cannot fail as the recent
changes to the lkb refcounting model does not require to evaluate the
return value to may call a put.

For the dlm_user_request() function we still need to know if the result
-EAGAIN was happening as the lkb lifetime ends to not add the lkb to the
ownqueue. This is the only user, we use a call-by-reference result
parameter to allow the user to know if the lkb lifetime ended
immediately on the lock request as dlm_user_request() requires.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/lock.c | 49 ++++++++++++++++++++++---------------------------
 1 file changed, 22 insertions(+), 27 deletions(-)

diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index 28c312410527..10058c89c811 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -83,7 +83,7 @@ static void send_grant(struct dlm_rsb *r, struct dlm_lkb *lkb);
 static void send_bast(struct dlm_rsb *r, struct dlm_lkb *lkb, int mode);
 static void send_lookup(struct dlm_rsb *r, struct dlm_lkb *lkb);
 static void send_remove(struct dlm_rsb *r);
-static int _request_lock(struct dlm_rsb *r, struct dlm_lkb *lkb);
+static void _request_lock(struct dlm_rsb *r, struct dlm_lkb *lkb, int *result);
 static void _cancel_lock(struct dlm_rsb *r, struct dlm_lkb *lkb);
 static void __receive_convert_reply(struct dlm_rsb *r, struct dlm_lkb *lkb,
 				    const struct dlm_message *ms, bool local);
@@ -2761,7 +2761,7 @@ static void process_lookup_list(struct dlm_rsb *r)
 
 	list_for_each_entry_safe(lkb, safe, &r->res_lookup, lkb_rsb_lookup) {
 		list_del_init(&lkb->lkb_rsb_lookup);
-		_request_lock(r, lkb);
+		_request_lock(r, lkb, NULL);
 		dlm_put_lkb(lkb);
 	}
 }
@@ -2796,7 +2796,7 @@ static void confirm_master(struct dlm_rsb *r, int error)
 					 lkb_rsb_lookup);
 			list_del_init(&lkb->lkb_rsb_lookup);
 			r->res_first_lkid = lkb->lkb_id;
-			_request_lock(r, lkb);
+			_request_lock(r, lkb, NULL);
 			dlm_put_lkb(lkb);
 		}
 		break;
@@ -3241,7 +3241,7 @@ static void do_cancel_effects(struct dlm_rsb *r, struct dlm_lkb *lkb,
 
 /* add a new lkb to a possibly new rsb, called by requesting process */
 
-static int _request_lock(struct dlm_rsb *r, struct dlm_lkb *lkb)
+static void _request_lock(struct dlm_rsb *r, struct dlm_lkb *lkb, int *result)
 {
 	int error;
 
@@ -3263,7 +3263,8 @@ static int _request_lock(struct dlm_rsb *r, struct dlm_lkb *lkb)
 		do_request_effects(r, lkb, error);
 	}
  out:
-	return error;
+	if (result)
+		*result = error;
 }
 
 /* change some property of an existing lkb, e.g. mode */
@@ -3332,7 +3333,7 @@ static void _cancel_lock(struct dlm_rsb *r, struct dlm_lkb *lkb)
 
 static int request_lock(struct dlm_ls *ls, struct dlm_lkb *lkb,
 			const void *name, int len,
-			struct dlm_args *args)
+			struct dlm_args *args, int *result)
 {
 	struct dlm_rsb *r;
 	int error;
@@ -3357,11 +3358,11 @@ static int request_lock(struct dlm_ls *ls, struct dlm_lkb *lkb,
 	attach_lkb(r, lkb);
 	lkb->lkb_lksb->sb_lkid = lkb->lkb_id;
 
-	error = _request_lock(r, lkb);
+	_request_lock(r, lkb, result);
 
 	unlock_rsb(r);
 	put_rsb(r);
-	return error;
+	return 0;
 }
 
 static int convert_lock(struct dlm_ls *ls, struct dlm_lkb *lkb,
@@ -3474,14 +3475,12 @@ int dlm_lock(dlm_lockspace_t *lockspace,
 	if (convert)
 		error = convert_lock(ls, lkb, &args);
 	else
-		error = request_lock(ls, lkb, name, namelen, &args);
+		error = request_lock(ls, lkb, name, namelen, &args, NULL);
 
  out_put:
 	trace_dlm_lock_end(ls, lkb, name, namelen, mode, flags, error, true);
 
 	__put_lkb(ls, lkb);
-	if (error == -EAGAIN || error == -EINPROGRESS)
-		error = 0;
  out:
 	dlm_unlock_recovery(ls);
 	dlm_put_lockspace(ls);
@@ -4486,7 +4485,7 @@ static int receive_request_reply(struct dlm_ls *ls,
 			queue_cast_overlap(r, lkb);
 			confirm_master(r, result);
 		} else {
-			_request_lock(r, lkb);
+			_request_lock(r, lkb, NULL);
 			if (r->res_master_nodeid == dlm_our_nodeid())
 				confirm_master(r, 0);
 		}
@@ -4772,7 +4771,7 @@ static void receive_lookup_reply(struct dlm_ls *ls,
 		goto out_list;
 	}
 
-	_request_lock(r, lkb);
+	_request_lock(r, lkb, NULL);
 
  out_list:
 	if (do_lookup_list)
@@ -5328,7 +5327,7 @@ int dlm_recover_waiters_post(struct dlm_ls *ls)
 			switch (mstype) {
 			case DLM_MSG_LOOKUP:
 			case DLM_MSG_REQUEST:
-				_request_lock(r, lkb);
+				_request_lock(r, lkb, NULL);
 				if (r->res_nodeid != -1 && is_master(r))
 					confirm_master(r, 0);
 				break;
@@ -5767,7 +5766,7 @@ int dlm_user_request(struct dlm_ls *ls, struct dlm_user_args *ua,
 {
 	struct dlm_lkb *lkb;
 	struct dlm_args args;
-	int error;
+	int error, result;
 
 	dlm_lock_recovery(ls);
 
@@ -5800,20 +5799,16 @@ int dlm_user_request(struct dlm_ls *ls, struct dlm_user_args *ua,
 	   When DLM_DFL_USER_BIT is set, the dlm knows that this is a userspace
 	   lock and that lkb_astparam is the dlm_user_args structure. */
 	set_bit(DLM_DFL_USER_BIT, &lkb->lkb_dflags);
-	error = request_lock(ls, lkb, name, namelen, &args);
+	error = request_lock(ls, lkb, name, namelen, &args, &result);
+	if (error)
+		goto out_put;
 
-	switch (error) {
-	case 0:
-		break;
-	case -EINPROGRESS:
-		error = 0;
-		break;
-	case -EAGAIN:
-		error = 0;
-		fallthrough;
-	default:
+	/* the lkb lifetime ended because request_lock() handled
+	 * internally an -EAGAIN, so we don't add it to the
+	 * ownqueue.
+	 */
+	if (result == -EAGAIN)
 		goto out_put;
-	}
 
 	/* add this new lkb to the per-process list of locks */
 	spin_lock_bh(&ua->proc->locks_spin);
-- 
2.43.0