drbd: remove usage of list iterator variable after loop

stable inclusion
from stable-v5.10.118
commit 5a19f3c2d3b6e5f5237cb79849626c85831a5fa9
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L686

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5a19f3c2d3b6e5f5237cb79849626c85831a5fa9

--------------------------------

[ Upstream commit 901aeda6 ]

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

Since that variable should not be used past the loop iteration, a
separate variable is used to 'remember the current location within the
loop'.

To either continue iterating from that position or skip the iteration
(if the previous iteration was complete) list_prepare_entry() is used.

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: NJakob Koschel <jakobkoschel@gmail.com>
Link: https://lore.kernel.org/r/20220331220349.885126-1-jakobkoschel@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

drivers/block/drbd/drbd_main.c

@@ -184,7 +184,7 @@ void tl_release(struct drbd_connection *connection, unsigned int barrier_nr,
 		unsigned int set_size)
 {
 	struct drbd_request *r;
-	struct drbd_request *req = NULL;
+	struct drbd_request *req = NULL, *tmp = NULL;
 	int expect_epoch = 0;
 	int expect_size = 0;
 
@@ -238,8 +238,11 @@ void tl_release(struct drbd_connection *connection, unsigned int barrier_nr,
 	 * to catch requests being barrier-acked "unexpectedly".
 	 * It usually should find the same req again, or some READ preceding it. */
 	list_for_each_entry(req, &connection->transfer_log, tl_requests)
-		if (req->epoch == expect_epoch)
+		if (req->epoch == expect_epoch) {
+			tmp = req;
 			break;
+		}
+	req = list_prepare_entry(tmp, &connection->transfer_log, tl_requests);
 	list_for_each_entry_safe_from(req, r, &connection->transfer_log, tl_requests) {
 		if (req->epoch != expect_epoch)
 			break;