[5.4] kernel panic when the referral server is not responding

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 5 Update 4
  • i686 (and probably x86_64 too).
  • kernel version: 2.6.18-164.el5 and 2.6.18-164.9.1.el5

Issue

  • [5.4] kernel panic when the referral server is not responding.
  • The kernel panic occurs after some seconds when a nfsv4 volume is mounted.

Resolution

Root Cause

  • There is a bug in fs/nfs/client.c

Diagnostic Steps

  • Following steps can easily reproduce the issue:

A. configure
     1. export nfs share directory at server side.
        # cat /etc/exports
          /nfsroot/nfsv4     127.0.0.1(rw,fsid=0,insecure,no_root_squash,nohide,crossmnt)
          /nfsroot/nfsv4/dir1     127.0.0.1(rw,insecure,no_root_squash,nohide,crossmnt,refer=/work@100.100.100.100)

  B. steps
     step1: # mkdir -p /nfsroot/nfsv4/dir1
     step2: # service nfs restart
     step3: # mount /dev/hda1 /nfsroot/nfsv4/dir1
     step4: # mount -t nfs4 -o timeo=10,retrans=1 127.0.0.1:/ /mnt
     step5: # ll /mnt

Note: In step3, a system seems to have a panic when some iso is loop mounted instead of an actual partition like hda1.

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