CIFS ISO Mount Disconnecting Intermittently

CIFS ISO Mount Disconnecting Intermittently

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Article ID: CTX132665

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Description

Mounting out ISO from a CIFS ISO Storage Repository (SR) disconnects intermittently, and causes boot ISOs to disappear and bounced servers unable to boot.

The /var/log/messages log is displayed as following:

CIFS VFS: No response for cmd 50 mid 3457
CIFS VFS: No response for cmd 50 mid 63007
CIFS VFS: No response for cmd 50 mid 55891
CIFS VFS: No response for cmd 50 mid 56839
CIFS VFS: No response for cmd 50 mid 56931
CIFS VFS: Send error in SessSetup = -11
CIFS VFS: No response to cmd 115 mid 2108
CIFS VFS: No response to cmd 115 mid 42833

Resolution

To resolve the issue, some CIFS module options have to be disabled. Complete the following procedure:

  1. Open XenCenter. Right-click the CIFS ISO SR and select Detach.

  2. Connect to the server and make sure that no CIFS module is loaded. To do this, complete the following procedure:

    1. Run lsmod | grep cifs | wc –l command on the console:
      If the result displays more than zero, it indicates that CIFS module is still loaded.

    2. To ensure all the CIFS SRs are detached, run the following command:
      modprobe –r cifs
      This command unloads the CIFS module.

  3. Run the following command to save /etc/modprobe.conf /etc/modprobe.conf.ori.[date]:
    cp /etc/modprobe.conf{,.date}

  4. Edit /etc/modprobe.conf by adding the following line at the end of the file:
    install cifs /sbin/modprobe --ignore-install cifs; /opt/scripts/disable_cifs_opt.sh;

  5. Create /opt/scripts/disable_cifs_opt.sh file and add the following lines to it:
    # disable LookupCacheEnable
    echo "0" > /proc/fs/cifs/LookupCacheEnabled
    # disable OplockEnabled
    echo "0" > /proc/fs/cifs/OplockEnabled
    # disable LinuxExtensionsEnabled
    echo "0" > /proc/fs/cifs/LinuxExtensionsEnabled

  6. Re-attach the CIFS SRs through XenCenter.

Notes:

  • LookupCacheEnable: This option is used to allow inode information to be cached for one second. 

  • OplockEnabled: Option for Opportunistic Locking. If set to 1 then distributed caching is enabled. It allows the client to cache the remote file locally on the client.

  • LinuxExtensionsEnabled: This option allows the use of CIFS Unix extension, optional protocol enhancement.

These options work well on most environments but might be unstable in some other environment because of network related issues.

Issue/Introduction

This document describe how to fix CIFS ISO problem causing boot.iso and other iso to get diconnected intermittently.
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