[LTP] [PATCH 3/5] fcntl42: test for F_SETLKW interruption case

[Alexander Aring <aahringo@redhat.com>]

This patch adds fcntl42 testcase to test on side effects, e.g. unlock
all acquired locks, when a lock request was interrupted by a signal.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 testcases/kernel/syscalls/fcntl/.gitignore |   2 +
 testcases/kernel/syscalls/fcntl/fcntl42.c  | 153 +++++++++++++++++++++
 2 files changed, 155 insertions(+)
 create mode 100644 testcases/kernel/syscalls/fcntl/fcntl42.c

diff --git a/testcases/kernel/syscalls/fcntl/.gitignore b/testcases/kernel/syscalls/fcntl/.gitignore
index 4bdae1a22..abffa2967 100644
--- a/testcases/kernel/syscalls/fcntl/.gitignore
+++ b/testcases/kernel/syscalls/fcntl/.gitignore
@@ -78,3 +78,5 @@
 /fcntl40_64
 /fcntl41
 /fcntl41_64
+/fcntl42
+/fcntl42_64
diff --git a/testcases/kernel/syscalls/fcntl/fcntl42.c b/testcases/kernel/syscalls/fcntl/fcntl42.c
new file mode 100644
index 000000000..4d66568fd
--- /dev/null
+++ b/testcases/kernel/syscalls/fcntl/fcntl42.c
@@ -0,0 +1,153 @@
+/*
+ * [Description]
+ * This test confirms that DLM posix locking has problems when a posix lock
+ * got interrupted every lock gets unlocked.
+ *
+ * man fcntl:
+ *
+ * F_SETLKW (struct flock *)
+ *  As for F_SETLK, but if a conflicting lock is held on  the  file,
+ *  then  wait  for that lock to be released.  If a signal is caught
+ *  while waiting, then the call is interrupted and (after the  signal
+ *  handler has returned) returns immediately (with return value -1 and
+ *  errno set to EINTR; see signal(7)).
+ *
+ * The above quote of the man page of fcntl() is what this testcase tests.
+ * particulary if it has side-effects of previously acquired locks.
+ *
+ * [How to use it]
+ * Call it with TMPDIR=/mnt ./fcntl42 where TMPDIR is a gfs2 mountpoint.
+ * Try it on other filesystems to compare results.
+ *
+ * [What's it doing]
+ *
+ * What this test does is (using dlm_controld interval range interpretation):
+ *
+ * parent:
+ *
+ * 1. lock[0-0]
+ *
+ * child:
+ *
+ * 2. lock[1-1]
+ * 3. lockw[0-0] - should block (see 1. parent), but we get interrupted by SIGALRM
+ *
+ * parent:
+ *
+ * 4. trylock[1-1] - should return -1 and errno -EAGAIN because the child
+ *                   should still have lock[1-1] acuired and this is what
+ *                   the child thinks to have. If it's successful the child
+ *                   wrongly assumes it has the lock[1-1] still acquired and
+ *                   the child process is still alive.
+ *
+ */
+
+#include <sys/wait.h>
+
+#include "tst_test.h"
+
+static int fd;
+
+static void catch_alarm(int num)
+{
+	(void)num;
+
+	tst_res(TINFO, "catch alarm");
+}
+
+void do_child1(void)
+{
+	struct flock fl = {
+		.l_type = F_WRLCK,
+		.l_whence = SEEK_SET,
+		.l_start = 1L,
+		.l_len = 1L,
+	};
+	struct sigaction act;
+	int rv;
+
+	SAFE_FCNTL(fd, F_SETLK, &fl);
+	tst_res(TINFO, "child locked lock 1-1");
+
+	fl.l_type = F_WRLCK;
+	fl.l_start = 0;
+	fl.l_len = 1;
+
+	memset(&act, 0, sizeof(act));
+	act.sa_handler = catch_alarm;
+	sigemptyset(&act.sa_mask);
+	sigaddset(&act.sa_mask, SIGALRM);
+	sigaction(SIGALRM, &act, NULL);
+
+	/* interrupt SETLKW by signal in 3 secs */
+	alarm(3);
+	rv = fcntl(fd, F_SETLKW, &fl);
+	if (rv == -1 && errno == EINTR)
+		tst_res(TPASS, "Child1 interrupted 0-0");
+
+	TST_CHECKPOINT_WAKE(1);
+	/* keep child alive until parent check region */
+	TST_CHECKPOINT_WAIT(2);
+}
+
+static void fcntl40_test(void)
+{
+	struct flock fl = {
+		.l_type = F_WRLCK,
+		.l_whence = SEEK_SET,
+		.l_start = 0L,
+		.l_len = 1L,
+	};
+	pid_t pid;
+	int rv;
+
+	SAFE_FCNTL(fd, F_SETLK, &fl);
+	tst_res(TINFO, "parent lock 0-0");
+
+	pid = SAFE_FORK();
+	if (pid == 0) {
+		do_child1();
+		tst_res(TINFO, "childs exits");
+		return;
+	}
+
+	TST_CHECKPOINT_WAIT(1);
+
+	fl.l_type = F_WRLCK;
+	fl.l_start = 1;
+	fl.l_len = 1;
+	rv = fcntl(fd, F_SETLK, &fl);
+	/* parent testing childs region, the child will think
+	 * it has region 1-1 locked because it was interrupted
+	 * by region 0-0. Due bugs the interruption also unlocked
+	 * region 1-1.
+	 */
+	if (rv == -1 && errno == EAGAIN)
+		tst_res(TPASS, "region 1-1 locked");
+	else
+		tst_res(TFAIL, "region 1-1 unlocked");
+
+	TST_CHECKPOINT_WAKE(2);
+
+	wait(NULL);
+	tst_res(TINFO, "parent exits");
+}
+
+static void setup(void)
+{
+	fd = SAFE_OPEN("filename", O_RDWR | O_CREAT, 0700);
+}
+
+static void cleanup(void)
+{
+	if (fd > -1)
+		SAFE_CLOSE(fd);
+}
+
+static struct tst_test test = {
+	.forks_child = 1,
+	.needs_checkpoints = 1,
+	.test_all = fcntl40_test,
+	.setup = setup,
+	.cleanup = cleanup,
+};
-- 
2.31.1


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