selftests: move dnotify_test from Documentation/filesystems

Move dnotify_test.c, Makefile, and .gitignore from Documentation/filesystems
to selftests/filesystems.

Remove filesystems build target from Documentation/Makefile and update
selftests/filesystems/Makefile to work under selftests. dnotify_test will
not be run as part of selftests suite and will not be included in install
targets. It can be built separately for now.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/filesystems/.gitignore

@@ -0,0 +1 @@
+dnotify_test

tools/testing/selftests/filesystems/Makefile

@@ -0,0 +1,7 @@
+TEST_PROGS := dnotify_test
+all: $(TEST_PROGS)
+
+include ../lib.mk
+
+clean:
+	rm -fr $(TEST_PROGS)

tools/testing/selftests/filesystems/dnotify_test.c

@@ -0,0 +1,34 @@
+#define _GNU_SOURCE	/* needed to get the defines */
+#include <fcntl.h>	/* in glibc 2.2 this has the needed
+				   values defined */
+#include <signal.h>
+#include <stdio.h>
+#include <unistd.h>
+
+static volatile int event_fd;
+
+static void handler(int sig, siginfo_t *si, void *data)
+{
+	event_fd = si->si_fd;
+}
+
+int main(void)
+{
+	struct sigaction act;
+	int fd;
+
+	act.sa_sigaction = handler;
+	sigemptyset(&act.sa_mask);
+	act.sa_flags = SA_SIGINFO;
+	sigaction(SIGRTMIN + 1, &act, NULL);
+
+	fd = open(".", O_RDONLY);
+	fcntl(fd, F_SETSIG, SIGRTMIN + 1);
+	fcntl(fd, F_NOTIFY, DN_MODIFY|DN_CREATE|DN_MULTISHOT);
+	/* we will now be notified if any of the files
+	   in "." is modified or new files are created */
+	while (1) {
+		pause();
+		printf("Got event on fd=%d\n", event_fd);
+	}
+}