New filesystem freeze API

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One Line Summary

Folproof filesystem freeze API for user space daemons and guest agents.


There are a few with issues with how filesystem freeze works in Linux:

- Unmounting: It is possible to umount a frozen filesystem. The problem is that there is no API to thaw an unmounted filesystem.

- There is no check API: There is no easy way to know whether a filesystem is frozen or not.

- Foolproofness: Quite often the freeze/thaw process is handled from a
daemon. In such cases we have to make really sure that the process does
not go away or is killed while the filesystem is frozen; there is no
check API so it is not always easy to figure out what is going on. With
the advent of virtualization things got even funnier; in some cases not
even the root user is aware of the existence of such daemon (usually a
guest agent that freezes the guests filesystems before taking a storage

In this session I would like to propose a new API that solves all the problems above and to discuss the addition of à la VSS functionality.

Presentation Materials



  • Fernando Luis Vazquez Cao

    NTT Open Source Software Center


    Fernando is a Linux developer based in Tokyo.His currents interests include virtualization, data center bridging technologies, and high performance networking and storage systems. He is currently a principal software engineer at NTT Open Software Center and senior consultant at NTT Data Intellilink, dividing his time between community open source work and his consulting and support duties at NTT.