2022-04-02 20:01:29

by Jakob Koschel

Subject: [PATCH 1/2] drbd: remove usage of list iterator variable after loop for list_for_each_entry_safe_from()

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: Jakob Koschel <[email protected]>
---
drivers/block/drbd/drbd_main.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 96881d5babd9..9676a1d214bc 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -171,7 +171,7 @@ 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;

@@ -225,8 +225,11 @@ 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;

base-commit: f82da161ea75dc4db21b2499e4b1facd36dab275
--
2.25.1

2022-04-05 01:34:27

by Jens Axboe

Subject: Re: [PATCH 1/2] drbd: remove usage of list iterator variable after loop for list_for_each_entry_safe_from()

On Fri, 1 Apr 2022 00:03:48 +0200, Jakob Koschel wrote:
> 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'.
>
> [...]

Applied, thanks!

[1/2] drbd: remove usage of list iterator variable after loop for list_for_each_entry_safe_from()
commit: 901aeda62efa21f2eae937bccb71b49ae531be06
[2/2] drbd: remove check of list iterator against head past the loop body
commit: 2651ee5ae43241831ca63d7158bb2b151a6a0e1f

Best regards,
--
Jens Axboe