From: Ian Kent <ikent@redhat.com>

For some reason, when umounting autofs mounts after closing the ioctl
file handle, the kernel can return EBUSY for some small amount of time.

This can cause umounts to incorrectly fail when in fact they should
succeed.

Retrying for about a second and a half seems to work quite well.

diff --git a/conf/umount/umount_linux.c b/conf/umount/umount_linux.c
index ea0e4e318c1ff3d2c4b267e6b58d1f89ef5e3764..873ecf23f662113563efb9845ba2dca8651997ca 100644 (file)
--- a/conf/umount/umount_linux.c
+++ b/conf/umount/umount_linux.c
@@ -59,6 +59,7 @@ umount_fs(char *mntdir, const char *mnttabname, u_int unmount_flags)
   char loopstr[] = "loop=";
   char *loopdev;
 #endif /* HAVE_LOOP_DEVICE */
+  unsigned int retries = 8;
 
   mp = mlist = read_mtab(mntdir, mnttabname);
 
@@ -91,6 +92,7 @@ umount_fs(char *mntdir, const char *mnttabname, u_int unmount_flags)
   unlock_mntlist();
 #endif /* MOUNT_TABLE_ON_FILE */
 
+again:
 #if defined(HAVE_UMOUNT2) && defined(MNT2_GEN_OPT_DETACH)
   /*
    * If user asked to try forced unmounts, then do a quick check to see if
@@ -108,6 +110,14 @@ umount_fs(char *mntdir, const char *mnttabname, u_int unmount_flags)
   } else
 #endif /* defined(HAVE_UMOUNT2) && defined(MNT2_GEN_OPT_DETACH) */
     error = UNMOUNT_TRAP(mp_save->mnt);
+
+  /* Linux kernel can be sluggish for some reason */
+  if (error == EBUSY && retries--) {
+    struct timespec tm = {0, 200000000};
+    nanosleep(&tm, NULL);
+    goto again;
+  }
+
   if (error < 0) {
     plog(XLOG_WARNING, "unmount(%s) failed: %m", mp_save->mnt->mnt_dir);
     switch ((error = errno)) {