test70: regression test for vfs race condition

Change-Id: I68681cdc5ed70491a08f5ddc86890fb2743c839d

test/Makefile

@@ -36,7 +36,7 @@ MINIX_TESTS= \
  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 \
 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 \
 41 42 43 44 45 46    48 49 50    52 53 54 55 56    58 59 60 \
-61       64 65 66 67 68 69
+61       64 65 66 67 68 69 70
 
 .if ${MACHINE_ARCH} == "i386"
 MINIX_TESTS+= \

test/test70.c

@@ -0,0 +1,78 @@
+/* Test 70
+ * Regression test for vfs overwriting m_out fields by competing threads.
+ * lseek() uses one of these fields too so this test performs concurrent
+ * lseek()s to trigger this situation.
+ */
+
+#include <time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+
+#define MAX_ERROR 2
+
+#include "common.c"
+
+#define SEEKWINDOW 1000
+
+static int
+doseeks(int seekbase)
+{
+	char template[30] = "tempfile.XXXXXXXX";
+	int iteration, fd = mkstemp(template);
+	int limit = seekbase + SEEKWINDOW;
+
+	/* make a temporary file, unlink it so it's always gone
+	 * afterwards, and make it the size we need.
+	 */
+	if(fd < 0) { perror("mkstemp"); e(2); return 1; }
+	if(unlink(template) < 0) { perror("unlink"); e(3); return 1; }
+	if(ftruncate(fd, limit) < 0) { perror("ftruncate"); e(4); return 1; }
+
+	/* try lseek() lots of times with different arguments and make
+	 * sure we get the right return value back, while this happens
+	 * in a concurrent process too.
+	 */
+#define ITERATIONS 10000
+	for(iteration = 0; iteration < ITERATIONS; iteration++) {
+		int o;
+		for(o = seekbase; o < limit; o++) {
+			int r;
+			if((r=lseek(fd, o, SEEK_SET)) != o) {
+				if(r < 0) perror("lseek");
+				fprintf(stderr, "%d/%d  %d != %d\n",
+					iteration, ITERATIONS, r, o);
+				e(5);
+				return 1;
+			}	
+		}
+	}
+
+	return 0;
+}
+
+int
+main()
+{
+  start(70);
+  pid_t f;
+  int result;
+
+  if((f=fork()) < 0) { e(1); quit(); }
+
+  if(f == 0) { exit(doseeks(0)); }
+
+  if(doseeks(SEEKWINDOW)) { e(10); }
+
+  if (waitpid(f, &result, 0) == -1) e(11);
+  if (WEXITSTATUS(result) != 0) e(12);
+
+  quit();
+
+  return(-1);			/* impossible */
+}
+