After nfs mounts were done on a system the sunrpc module 'use counter' stays positive, preventing unloading of the module
Environment
- Red Hat Enterprise Linux 6.0, 6.1 and 6.2
Issue
Once an NFS share was mounted the sunrpc module used counter
always stays positive, preventing unloading of the module.
Resolution
Please install the kernel package in version 2.6.32-279
(which is part of RHEL6.3) or later to solve the issue.
Root Cause
A kernel bug is preventing the used counter from properly beeing handled.
Diagnostic Steps
- To procedure to see the issue on affected kernels, using a system with no sunrpc/nfs modules loaded:
modprobe sunrpc # increases used counter to 1 (it mounts /var/lib/nfs/rpc_pipefs)
mount server:/mnt/export /mnt/tmp # this increases the sunrpc used counter from 5 to 14
umount /mnt/tmp # decreases 14 to 8 which is the problem
rmmod auth_rpcgss nfs_acl lockd nfs # decreases by 5
umount /var/lib/nfs/rpc_pipefs # decreases by 1, sunrpc usage counter is at 3 and the module can not be unloaded properly
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