[LTP] [PATCH] fanotify: Fix broken tests due to fanotify_events_supported_by_kernel()

[Jan Kara]

When LTP test is run with CWD in btrfs subvolume, tests like fanotify16
fail with:

fanotify.h:169: TBROK: fanotify_mark (3, FAN_MARK_ADD, ..., AT_FDCWD, ".") failed: EXDEV (18)

This is because fanotify_events_supported_by_kernel() try to place a
mark onto CWD and that is forbidden for btrfs subvolumes. Change
fanotify_events_supported_by_kernel() to use "/" instead of "." which
has higher chances of working for btrfs.

Also update the error message to provide a bit more info.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 testcases/kernel/syscalls/fanotify/fanotify.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/testcases/kernel/syscalls/fanotify/fanotify.h b/testcases/kernel/syscalls/fanotify/fanotify.h
index 32b510cdc178..f2fe0c05b449 100644
--- a/testcases/kernel/syscalls/fanotify/fanotify.h
+++ b/testcases/kernel/syscalls/fanotify/fanotify.h
@@ -161,12 +161,13 @@ static inline int fanotify_events_supported_by_kernel(uint64_t mask,
 
 	fd = SAFE_FANOTIFY_INIT(init_flags, O_RDONLY);
 
-	if (fanotify_mark(fd, FAN_MARK_ADD | mark_flags, mask, AT_FDCWD, ".") < 0) {
+	if (fanotify_mark(fd, FAN_MARK_ADD | mark_flags, mask, AT_FDCWD, "/") < 0) {
 		if (errno == EINVAL) {
 			rval = -1;
 		} else {
 			tst_brk(TBROK | TERRNO,
-				"fanotify_mark (%d, FAN_MARK_ADD, ..., AT_FDCWD, \".\") failed", fd);
+				"fanotify_mark (%d, FAN_MARK_ADD | %x, %llx, AT_FDCWD, \".\") failed",
+				fd, mark_flags, (unsigned long long)mask);
 		}
 	}
 
-- 
2.35.3