#include <sys/stat.h>
#include <sys/vfs.h>
#include <sys/stat.h>
+#include <sys/file.h>
#include <unistd.h>
#include <stdbool.h>
#include <stdlib.h>
static void validate_export(nfs_export *exp);
static int matchhostname(const char *hostname1, const char *hostname2);
static void export_d_read(const char *dname);
+static void grab_lockfile(void);
+static void release_lockfile(void);
+
+static const char *lockfile = EXP_LOCKFILE;
+static int _lockfd = -1;
+
+/*
+ * If we aren't careful, changes made by exportfs can be lost
+ * when multiple exports process run at once:
+ *
+ * exportfs process 1 exportfs process 2
+ * ------------------------------------------
+ * reads etab version A reads etab version A
+ * adds new export B adds new export C
+ * writes A+B writes A+C
+ *
+ * The locking in support/export/xtab.c will prevent mountd from
+ * seeing a partially written version of etab, and will prevent
+ * the two writers above from writing simultaneously and
+ * corrupting etab, but to prevent problems like the above we
+ * need these additional lockfile() routines.
+ */
+static void
+grab_lockfile()
+{
+ _lockfd = open(lockfile, O_CREAT|O_RDWR, 0666);
+ if (_lockfd != -1)
+ lockf(_lockfd, F_LOCK, 0);
+}
+static void
+release_lockfile()
+{
+ if (_lockfd != -1)
+ lockf(_lockfd, F_ULOCK, 0);
+}
int
main(int argc, char **argv)
return 0;
}
}
+
+ /*
+ * Serialize things as best we can
+ */
+ grab_lockfile();
+ atexit(release_lockfile);
+
if (f_export && ! f_ignore) {
export_read(_PATH_EXPORTS);
export_d_read(_PATH_EXPORTS_D);
n = scandir(dname, &namelist, NULL, versionsort);
- if (n < 0)
+ if (n < 0) {
+ if (errno == ENOENT)
+ /* Silently return */
+ return;
xlog(L_NOTICE, "scandir %s: %s", dname, strerror(errno));
- else if (n == 0)
+ } else if (n == 0)
return;
for (i = 0; i < n; i++) {