Some NFS file transfers fail and hang automounting

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* This incident occurs with: <pre>sunrpc.tcp_slot_table_entries = 16</pre>
* This incident occurs with: <pre>sunrpc.tcp_slot_table_entries = 16</pre>
* This incident does NOT occur with: <pre>sunrpc.tcp_slot_table_entries = 32</pre>
* This incident does NOT occur with: <pre>sunrpc.tcp_slot_table_entries = 32</pre>
== Cause ==
== Resolution ==
== Resolution ==

Revision as of 15:08, 22 October 2010



  • Kernel version:
  • Bug 126213
  • Reported by: Philippe Dax (June 15, 2010)
  • Fixed by: Trond Myklebust (June 16, 2010)


  • Given a file "foo" of 50Mb on a remote machine "remote".
    • This command will never finish
      <localmachine $> cp /remote_mount_point/foo bar 
    • bar will have a size less than foo.
    • automounting of the local machine is hung.
  • The following message will show up in /var/log/messages
kernel: Callback slot table overflowed
  • The problem doesn't occur if foo has a size less than 10Mb
  • The final size of bar appears to be random
  • This incident occurs with:
    sunrpc.tcp_slot_table_entries = 16
  • This incident does NOT occur with:
    sunrpc.tcp_slot_table_entries = 32



This problem was fixed by:

commit b76ce56192bcf618013fb9aecd83488cffd645cc
Author: Trond Myklebust <>
Date:   Wed Jun 16 13:57:32 2010 -0400

    SUNRPC: Fix a re-entrancy bug in xs_tcp_read_calldir()
    If the attempt to read the calldir fails, then instead of storing the read
    bytes, we currently discard them. This leads to a garbage final result when
    upon re-entry to the same routine, we read the remaining bytes.
    Fixes the regression in bugzilla number 16213. Please see
    Signed-off-by: Trond Myklebust <>
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