IJ35947: NFS4:DIFFERENT MOUNTS USING SAME EXPORTED DIR CAN CAUSE A HANG.

APAR status

• Closed as fixed if next.

Error description

• If there are tow different mounts using the same exported
  directory, it is possible for the two mounts to use the
  same open owner.
  If the same open owner is used for the same file in the
  two different mounts, then it looks like the same open
  to a server.
  1) Mount the same share on two dirs:
  # Make sure that the share has at least 63 regular files.
  In the following test, files named "a" and "f0", "f1",
  "f2"... "f61"
  
  # mount -o vers=4 srvr:/share /mnt
  
  # mount -o vers=4 srvr:/share /mnt1
  
  2) Open a file in /mnt and leave it open:
  
  # ./op /mnt/a &
       ### ./op just opens a file and goes to sleep
  
  
  3) Open exactly 62 other files (other than /mnt/a)
   from /mnt. They can be closed:
  
  # i=0 ; while [ $i -le 61 ]
  
  do
  
  ./opcl /mnt/f${i}  #### ./opcl opens a file,
   closes it, and exits
  
  let i+=1
  
  done
  
   4) Open file "a" from the other mount - /mnt1:
  
  # ./op /mnt1/a &
  
  5) Kill the 1st process - it will try to
  close /mnt/a, and that close() will hang.
  
  # fg %1
  
  ./op /mnt/a
  
  [press ctrl + c] - It won't respond. And the KDB
  stack will show that it is looping in nfs4_close.
  

Local fix

• Use NFS3 or use single mount point.
  

Problem summary

• When the same exported share is mounted on two different mount
  points on the same client, there can be a conflict in the
  open-owners for some files, which could then lead to an
  infinite cycle of old-stateid errors and recovery. This would
  cause applications accessing the mounts to hang.
  

Problem conclusion

Temporary fix

Comments

• This APAR is being closed FIN. This means that a solution to
  this APAR is expected to be delivered from IBM in a release
  (if any) to be available within the next 24 months.
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  IJ36214 IJ36481

Fix information

Applicable component levels