Messages in this thread | | | Date | Fri, 1 Apr 2022 00:28:19 +0200 | Subject | Re: [Drbd-dev] [PATCH 2/2] drbd: remove check of list iterator against head past the loop body | From | Christoph Böhmwalder <> |
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Am 01.04.22 um 00:03 schrieb Jakob Koschel: > When list_for_each_entry() completes the iteration over the whole list > without breaking the loop, the iterator value will be a bogus pointer > computed based on the head element. > > While it is safe to use the pointer to determine if it was computed > based on the head element, either with list_entry_is_head() or > &pos->member == head, using the iterator variable after the loop should > be avoided. > > 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]. > > Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1] > Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com> > --- > drivers/block/drbd/drbd_req.c | 42 ++++++++++++++++++++++------------- > 1 file changed, 27 insertions(+), 15 deletions(-) > > diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c > index c04394518b07..b2571dc77fe6 100644 > --- a/drivers/block/drbd/drbd_req.c > +++ b/drivers/block/drbd/drbd_req.c > @@ -332,17 +332,21 @@ static void set_if_null_req_next(struct drbd_peer_device *peer_device, struct dr > static void advance_conn_req_next(struct drbd_peer_device *peer_device, struct drbd_request *req) > { > struct drbd_connection *connection = peer_device ? peer_device->connection : NULL; > + struct drbd_request *iter = req; > if (!connection) > return; > if (connection->req_next != req) > return; > - list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) { > - const unsigned s = req->rq_state; > - if (s & RQ_NET_QUEUED) > + > + req = NULL; > + list_for_each_entry_continue(iter, &connection->transfer_log, tl_requests) { > + const unsigned int s = iter->rq_state; > + > + if (s & RQ_NET_QUEUED) { > + req = iter; > break; > + } > } > - if (&req->tl_requests == &connection->transfer_log) > - req = NULL; > connection->req_next = req; > } > > @@ -358,17 +362,21 @@ static void set_if_null_req_ack_pending(struct drbd_peer_device *peer_device, st > static void advance_conn_req_ack_pending(struct drbd_peer_device *peer_device, struct drbd_request *req) > { > struct drbd_connection *connection = peer_device ? peer_device->connection : NULL; > + struct drbd_request *iter = req; > if (!connection) > return; > if (connection->req_ack_pending != req) > return; > - list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) { > - const unsigned s = req->rq_state; > - if ((s & RQ_NET_SENT) && (s & RQ_NET_PENDING)) > + > + req = NULL; > + list_for_each_entry_continue(iter, &connection->transfer_log, tl_requests) { > + const unsigned int s = iter->rq_state; > + > + if ((s & RQ_NET_SENT) && (s & RQ_NET_PENDING)) { > + req = iter; > break; > + } > } > - if (&req->tl_requests == &connection->transfer_log) > - req = NULL; > connection->req_ack_pending = req; > } > > @@ -384,17 +392,21 @@ static void set_if_null_req_not_net_done(struct drbd_peer_device *peer_device, s > static void advance_conn_req_not_net_done(struct drbd_peer_device *peer_device, struct drbd_request *req) > { > struct drbd_connection *connection = peer_device ? peer_device->connection : NULL; > + struct drbd_request *iter = req; > if (!connection) > return; > if (connection->req_not_net_done != req) > return; > - list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) { > - const unsigned s = req->rq_state; > - if ((s & RQ_NET_SENT) && !(s & RQ_NET_DONE)) > + > + req = NULL; > + list_for_each_entry_continue(iter, &connection->transfer_log, tl_requests) { > + const unsigned int s = iter->rq_state; > + > + if ((s & RQ_NET_SENT) && !(s & RQ_NET_DONE)) { > + req = iter; > break; > + } > } > - if (&req->tl_requests == &connection->transfer_log) > - req = NULL; > connection->req_not_net_done = req; > } >
Hi Jakob,
Both of these look good to me, thanks.
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Regards, Christoph
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