--- /dev/null
+/* We save the locks so we can reaquire them. */
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <ccan/tap/tap.h>
+
+struct lock {
+ struct lock *next;
+ unsigned int off;
+ unsigned int len;
+ int type;
+};
+static struct lock *locks;
+int locking_errors = 0;
+void (*unlock_callback)(int fd);
+
+int fcntl_with_lockcheck(int fd, int cmd, ... /* arg */ )
+{
+ va_list ap;
+ int ret, arg3;
+ struct flock *fl;
+
+ if (cmd != F_SETLK && cmd != F_SETLKW) {
+ /* This may be totally bogus, but we don't know in general. */
+ va_start(ap, cmd);
+ arg3 = va_arg(ap, int);
+ va_end(ap);
+
+ return fcntl(fd, cmd, arg3);
+ }
+
+ va_start(ap, cmd);
+ fl = va_arg(ap, struct flock *);
+ va_end(ap);
+
+ if (fl->l_type == F_UNLCK) {
+ struct lock **l;
+ struct lock *old = NULL;
+
+ for (l = &locks; *l; l = &(*l)->next) {
+ if ((*l)->off == fl->l_start
+ && (*l)->len == fl->l_len) {
+ old = *l;
+ *l = (*l)->next;
+ free(old);
+ break;
+ }
+ }
+ if (!old) {
+ diag("Unknown unlock %u@%u",
+ (int)fl->l_len, (int)fl->l_start);
+ locking_errors++;
+ }
+ } else {
+ struct lock *new, *i;
+ unsigned int fl_end = fl->l_start + fl->l_len;
+ if (fl->l_len == 0)
+ fl_end = (unsigned int)-1;
+
+ /* Check for overlaps: we shouldn't do this. */
+ for (i = locks; i; i = i->next) {
+ unsigned int i_end = i->off + i->len;
+ if (i->len == 0)
+ i_end = (unsigned int)-1;
+
+ if (fl->l_start >= i->off && fl->l_start < i_end)
+ break;
+ if (fl_end >= i->off && fl_end < i_end)
+ break;
+ }
+ if (i) {
+ diag("%s lock %u@%u overlaps %u@%u",
+ fl->l_type == F_WRLCK ? "write" : "read",
+ (int)fl->l_len, (int)fl->l_start,
+ i->len, (int)i->off);
+ locking_errors++;
+ }
+ new = malloc(sizeof *new);
+ new->off = fl->l_start;
+ new->len = fl->l_len;
+ new->type = fl->l_type;
+ new->next = locks;
+ locks = new;
+ }
+
+ ret = fcntl(fd, cmd, fl);
+ if (ret == 0 && fl->l_type == F_UNLCK && unlock_callback)
+ unlock_callback(fd);
+ return ret;
+}
+
+int forget_locking(void)
+{
+ unsigned int num = 0;
+ while (locks) {
+ struct lock *next = locks->next;
+ free(locks);
+ locks = next;
+ num++;
+ }
+ return num;
+}