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NFS Share got removed from NAS Filer without first unmounting it from Client causing df to hang indefinitely even if 'noitr' mount option is specified with 'hard' link option (Doc ID 2456376.1)

Last updated on JUNE 02, 2020

Applies to:

Linux OS - Version Oracle Linux 6.0 to Oracle Linux 7.5 [Release OL6 to OL7U5]
Linux x86
Linux x86-64

Symptoms

NAS Filer Admin removed back-end share which was still mounted on Oracle Linux client system.
df -ak commands are hanging in d-state and never finish

# df -ak
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/VGExaDb-LVDbSys1 72248648 32103260 36475884 47% /
tmpfs 264153088 38400 264114688 1% /dev/shm
/dev/sda1 516040 41384 448444 9% /boot
/dev/mapper/VGExaDb-LVDbOra1 103212320 80531688 17437752 83% /u01
/dev/mapper/VGExaDb-LVDbOra2 412849328 193303812 198573996 50% /u02
/dev/mapper/VGExaDb-LVDbOra3 412849328 255390584 136487224 66% /u03
^ccccccc

ps axl | awk '$10 ~ /D/'
root 359626 0.0 0.0 0 0 ? D Oct04 0:00 df -ak
root 359626 0.0 0.0 0 0 ? D Oct04 0:00 df -ak
root 359626 0.0 0.0 0 0 ? D Oct04 0:00 df -ak
root 359626 0.0 0.0 0 0 ? D Oct04 0:00 df -ak

From NFS manual hard option should give up if initr option is specified:

If hard is specified, the user cannot terminate the process waiting for the NFS communication to resume unless the intr option is also specified.

Mount is actually hard mounted but utilize as well initr:

1.X0.X0.X1:/backup on /backup type nfs (rw,sync,hard,intr,vers=4,addr=1.X0.X0.X1,clientaddr=1.X0.X0.X4)

Intr flag explanation:

intr / nointr Selects whether to allow signals to interrupt file operations on this mount point. If neither
option is specified (or if nointr is specified), signals do not interrupt NFS file operations.
If intr is specified, system calls return EINTR if an in-progress NFS operation is interrupted
by a signal.

Using the intr option is preferred to using the soft option because it is significantly less
likely to result in data corruption.

Why still all commands like df/ls/cd are hanging?

Cause

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In this Document
Symptoms
Cause
Solution


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