linux-kernel - [PATCH 1/2] dlm: remove usage of list iterator for list

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Date:   Fri,  1 Apr 2022 00:00:12 +0200
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Christine Caulfield <ccaulfie@...hat.com>
Cc:     David Teigland <teigland@...hat.com>, cluster-devel@...hat.com,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...nel.org>,
        "Brian Johannesmeyer" <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jakobkoschel@...il.com>
Subject: [PATCH 1/2] dlm: remove usage of list iterator for list_add() after the loop body

In preparation to limit the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].

Before, the code implicitly used the head when no element was found
when using &pos->list. Since the new variable is only set if an
element was found, the list_add() is performed within the loop
and only done after the loop if it is done on the list head directly.

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
---
 fs/dlm/lock.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index bdb51d209ba2..66e92617d7ea 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -1306,13 +1306,17 @@ static inline void unhold_lkb(struct dlm_lkb *lkb)
 static void lkb_add_ordered(struct list_head *new, struct list_head *head,
 			    int mode)
 {
-	struct dlm_lkb *lkb = NULL;
+	struct dlm_lkb *lkb = NULL, *iter;
 
-	list_for_each_entry(lkb, head, lkb_statequeue)
-		if (lkb->lkb_rqmode < mode)
+	list_for_each_entry(iter, head, lkb_statequeue)
+		if (iter->lkb_rqmode < mode) {
+			lkb = iter;
+			list_add_tail(new, &iter->lkb_statequeue);
 			break;
+		}
 
-	__list_add(new, lkb->lkb_statequeue.prev, &lkb->lkb_statequeue);
+	if (!lkb)
+		list_add_tail(new, head);
 }
 
 /* add/remove lkb to rsb's grant/convert/wait queue */

base-commit: f82da161ea75dc4db21b2499e4b1facd36dab275
-- 
2.25.1