[LTP] [PATCH v1] fanotify22.c: handle multiple asynchronous error events

[Wei Gao]

Since the introduction of the asynchronous fserror reporting framework
(kernel commit 81d2e13a57c9), fanotify22 has encountered sporadic failures
due to the non-deterministic nature of event delivery and merging:

1) tcase3 failure: A race condition occurs when the test reads the
   notification fd between two events. Adding a short delay
   (usleep) ensures all events are dispatched and ready before the
   read() call.

2) tcase4 failure: The kernel may deliver errors as independent events
   instead of a single merged event, The test logic is updated to
   validate the expected error_count by either a single merged event
   or the accumulation of multiple independent events in the buffer.

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202602042124.87bd00e3-lkp@intel.com
Signed-off-by: Wei Gao <wegao@suse.com>
---
 .../kernel/syscalls/fanotify/fanotify22.c     | 32 ++++++++++++++++---
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/testcases/kernel/syscalls/fanotify/fanotify22.c b/testcases/kernel/syscalls/fanotify/fanotify22.c
index 6578474a7..82eed7ba9 100644
--- a/testcases/kernel/syscalls/fanotify/fanotify22.c
+++ b/testcases/kernel/syscalls/fanotify/fanotify22.c
@@ -53,6 +53,8 @@ static struct fanotify_fid_t null_fid;
 static struct fanotify_fid_t bad_file_fid;
 static struct fanotify_fid_t bad_link_fid;
 
+static int event_count;
+
 static void trigger_fs_abort(void)
 {
 	SAFE_MOUNT(tst_device->dev, MOUNT_PATH, tst_device->fs_type,
@@ -88,7 +90,6 @@ static void trigger_bad_link_lookup(void)
 			ret, BAD_LINK, errno, EUCLEAN);
 }
 
-
 static void tcase3_trigger(void)
 {
 	trigger_bad_link_lookup();
@@ -176,9 +177,10 @@ static int check_error_event_info_error(struct fanotify_event_info_error *info_e
 {
 	int fail = 0;
 
-	if (info_error->error_count != ex->error_count) {
-		tst_res(TFAIL, "%s: Unexpected error_count (%d!=%d)",
-			ex->name, info_error->error_count, ex->error_count);
+	if (info_error->error_count != ex->error_count && event_count != ex->error_count) {
+		tst_res(TFAIL, "%s: Unexpected error_count (%d!=%d && %d!=%d)",
+			ex->name, info_error->error_count, ex->error_count,
+			event_count, ex->error_count);
 		fail++;
 	}
 
@@ -255,8 +257,30 @@ static void do_test(unsigned int i)
 
 	tcase->trigger_error();
 
+	usleep(100000);
+
 	read_len = SAFE_READ(0, fd_notify, event_buf, BUF_SIZE);
 
+	struct fanotify_event_metadata *metadata;
+	size_t len = read_len;
+
+	event_count = 0;
+
+	for (metadata = (struct fanotify_event_metadata *)event_buf;
+			FAN_EVENT_OK(metadata, len);
+			metadata = FAN_EVENT_NEXT(metadata, len)) {
+		event_count++;
+		struct fanotify_event_info_error *info_error = get_event_info_error(metadata);
+
+		if (info_error) {
+			tst_res(TINFO, "Event [%d]: errno=%d (expected %d), error_count=%d (expected total %d)",
+					event_count, info_error->error, tcase->error,
+					info_error->error_count, tcase->error_count);
+		} else {
+			tst_res(TINFO, "Event [%d]: No error info record found", event_count);
+		}
+	}
+
 	SAFE_FANOTIFY_MARK(fd_notify, FAN_MARK_REMOVE|FAN_MARK_FILESYSTEM,
 			   FAN_FS_ERROR, AT_FDCWD, MOUNT_PATH);
 
-- 
2.52.0