Hello,
When I was investigating the "recovery of busy mounts" problem, I
discovered that the proposed fix was not working with some versions
of nfs-utils. Turns out that the issue is caused by inconsistencies
in the umount return codes: different versions of umount and
umount.nfs return different error codes when failing to unmount
a busy volume. Some examples:
== nfs-client-1.2.6 (latest openSUSE), nfs-client-1.2.3 (SLES 11-SP2, RHEL6)
/mnt # umount .
umount.nfs: /mnt: device is busy
# echo $?
16
/mnt # umount .
umount.nfs4: /mnt: device is busy
# echo $?
16
== util-linux-2.21.2 (latest openSUSE)
/boot # umount .
umount: /boot: target is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))
/boot # echo $?
32
== util-linux-2.12r or 2.13 (SLES 10-SP4, RHEL5)
/mnt # umount .
umount: /mnt: device is busy
umount: /mnt: device is busy
n65:/mnt # echo $?
1
AutoFS interprets return code '16' as MTAB_NOTUPDATED (the volume
was unmounted but /etc/mtab was not updated accordingly), and it
seems this used to work with older versions of umount/umount.nfs.
With newer versions it causes trouble because spawn_umount()
will consider ret code 16 as not fatal, and return success:
626 /* This is not a fatal error */
627 if (ret == MTAB_NOTUPDATED) {
628 warn(logopt, "Unable to update the mtab file, /proc/mounts "
629 "and /etc/mtab will differ");
630 ret = 0;
631 }
The real problem is in nfs-utils and util-linux (which should eventually
agree on the return codes), however now we have all these versions
on the wild and AutoFS might fail with some of them.
For now, I'm using the following patch here to avoid accepting EBUSY
as non-fatal:
diff --git a/daemon/spawn.c b/daemon/spawn.c
index 3b4a009..cd1193d 100644
--- a/daemon/spawn.c
+++ b/daemon/spawn.c
@@ -623,11 +623,9 @@ int spawn_umount(unsigned logopt, ...)
}
}
- /* This is not a fatal error */
if (ret == MTAB_NOTUPDATED) {
warn(logopt, "Unable to update the mtab file, /proc/mounts "
"and /etc/mtab will differ");
- ret = 0;
}
return ret;
Ian, do you think AutoFS should adapt to the new return codes or
should I start reporting these problems to util-linux/libmount/nfs-utils
maintainers?
Thanks,
Leonardo
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