[PATCH 2/3] selftests/mm: refactor uffd_poll_thread to allow custom fault handlers

[Axel Rasmussen <axelrasmussen@google.com>]

Previously, we had "one fault handler to rule them all", which used
several branches to deal with all of the scenarios required by all of
the various tests.

In upcoming patches, I plan to add a new test, which has its own
slightly different fault handling logic. Instead of continuing to add
cruft to the existing fault handler, let's allow tests to define custom
ones, separate from other tests.

Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
---
 tools/testing/selftests/mm/uffd-common.c | 5 ++++-
 tools/testing/selftests/mm/uffd-common.h | 3 +++
 tools/testing/selftests/mm/uffd-stress.c | 6 ++----
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c
index 61c6250adf93..c9756dbffe7d 100644
--- a/tools/testing/selftests/mm/uffd-common.c
+++ b/tools/testing/selftests/mm/uffd-common.c
@@ -499,6 +499,9 @@ void *uffd_poll_thread(void *arg)
 	int ret;
 	char tmp_chr;
 
+	if (!args->handle_fault)
+		args->handle_fault = uffd_handle_page_fault;
+
 	pollfd[0].fd = uffd;
 	pollfd[0].events = POLLIN;
 	pollfd[1].fd = pipefd[cpu*2];
@@ -527,7 +530,7 @@ void *uffd_poll_thread(void *arg)
 			err("unexpected msg event %u\n", msg.event);
 			break;
 		case UFFD_EVENT_PAGEFAULT:
-			uffd_handle_page_fault(&msg, args);
+			args->handle_fault(&msg, args);
 			break;
 		case UFFD_EVENT_FORK:
 			close(uffd);
diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h
index 6068f2346b86..b28d88b9937e 100644
--- a/tools/testing/selftests/mm/uffd-common.h
+++ b/tools/testing/selftests/mm/uffd-common.h
@@ -77,6 +77,9 @@ struct uffd_args {
 	unsigned long missing_faults;
 	unsigned long wp_faults;
 	unsigned long minor_faults;
+
+	/* A custom fault handler; defaults to uffd_handle_page_fault. */
+	void (*handle_fault)(struct uffd_msg *msg, struct uffd_args *args);
 };
 
 struct uffd_test_ops {
diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index f1ad9eef1c3a..47e1464935a8 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -199,10 +199,8 @@ static int stress(struct uffd_args *args)
 				   locking_thread, (void *)cpu))
 			return 1;
 		if (bounces & BOUNCE_POLL) {
-			if (pthread_create(&uffd_threads[cpu], &attr,
-					   uffd_poll_thread,
-					   (void *)&args[cpu]))
-				return 1;
+			if (pthread_create(&uffd_threads[cpu], &attr, uffd_poll_thread, &args[cpu]))
+				err("uffd_poll_thread create");
 		} else {
 			if (pthread_create(&uffd_threads[cpu], &attr,
 					   uffd_read_thread,
-- 
2.40.1.606.ga4b1b128d6-goog