[PATCH 2/5] module/dups: Inform duplicate requests about the result directly

[Petr Pavlu]

When kmod_dup_request_announce() announces the completion of
a request_module() call to duplicate waiters, it queues a work item to
invoke kmod_dup_request_complete(), and only that function calls
complete_all().

This adds an arbitrary delay that is unnecessary and provides little
benefit. Call complete_all() directly from kmod_dup_request_announce()
instead.

Signed-off-by: Petr Pavlu <petr.pavlu@xxxxxxxx>
---
 kernel/module/dups.c | 50 +++++++++++---------------------------------
 1 file changed, 12 insertions(+), 38 deletions(-)

diff --git a/kernel/module/dups.c b/kernel/module/dups.c
index e1828e865edd..f0bdd7560d7e 100644
--- a/kernel/module/dups.c
+++ b/kernel/module/dups.c
@@ -48,7 +48,6 @@ struct kmod_dup_req {
 	struct list_head list;
 	char name[MODULE_NAME_LEN];
 	struct completion first_req_done;
-	struct work_struct complete_work;
 	struct delayed_work delete_work;
 	int dup_ret;
 };
@@ -105,29 +104,6 @@ static void kmod_dup_request_delete(struct work_struct *work)
 	put_kmod_req(kmod_req);
 }
 
-static void kmod_dup_request_complete(struct work_struct *work)
-{
-	struct kmod_dup_req *kmod_req;
-
-	kmod_req = container_of(work, struct kmod_dup_req, complete_work);
-
-	/*
-	 * This will ensure that the kernel will let all the waiters get
-	 * informed its time to check the return value. It's time to
-	 * go home.
-	 */
-	complete_all(&kmod_req->first_req_done);
-
-	/*
-	 * Now that we have allowed prior request_module() calls to go on
-	 * with life, let's schedule deleting this entry. We don't have
-	 * to do it right away, but we *eventually* want to do it so to not
-	 * let this linger forever as this is just a boot optimization for
-	 * possible abuses of vmalloc() incurred by finit_module() thrashing.
-	 */
-	queue_delayed_work(system_dfl_wq, &kmod_req->delete_work, 60 * HZ);
-}
-
 bool kmod_dup_request_exists_wait(char *module_name, bool wait, int *dup_ret)
 {
 	struct kmod_dup_req *kmod_req, *new_kmod_req;
@@ -143,7 +119,6 @@ bool kmod_dup_request_exists_wait(char *module_name, bool wait, int *dup_ret)
 
 	refcount_set(&new_kmod_req->refcount, 1);
 	memcpy(new_kmod_req->name, module_name, strlen(module_name));
-	INIT_WORK(&new_kmod_req->complete_work, kmod_dup_request_complete);
 	INIT_DELAYED_WORK(&new_kmod_req->delete_work, kmod_dup_request_delete);
 	init_completion(&new_kmod_req->first_req_done);
 
@@ -246,23 +221,22 @@ void kmod_dup_request_announce(char *module_name, int ret)
 	 * that is owned by the current task.
 	 */
 	kmod_req = kmod_dup_request_lookup(module_name);
+	mutex_unlock(&kmod_dup_mutex);
+
 	if (!kmod_req)
-		goto out;
+		return;
 
 	kmod_req->dup_ret = ret;
 
+	/* Inform all the duplicate waiters to check the return value. */
+	complete_all(&kmod_req->first_req_done);
+
 	/*
-	 * If we complete() here we may allow duplicate threads
-	 * to continue before the first one that submitted the
-	 * request. We're in no rush also, given that each and
-	 * every bounce back to userspace is slow we avoid that
-	 * with a slight delay here. So queueue up the completion
-	 * and let duplicates suffer, just wait a tad bit longer.
-	 * There is no rush. But we also don't want to hold the
-	 * caller up forever or introduce any boot delays.
+	 * Now that we have allowed prior request_module() calls to go on
+	 * with life, let's schedule deleting this entry. We don't have
+	 * to do it right away, but we *eventually* want to do it so to not
+	 * let this linger forever as this is just a boot optimization for
+	 * possible abuses of vmalloc() incurred by finit_module() thrashing.
 	 */
-	queue_work(system_dfl_wq, &kmod_req->complete_work);
-
-out:
-	mutex_unlock(&kmod_dup_mutex);
+	queue_delayed_work(system_dfl_wq, &kmod_req->delete_work, 60 * HZ);
 }
-- 
2.54.0