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SubjectRe: [RFC 1/4] fs: Add generic file system event notifications
On 15.04.2015 09:15, Beata Michalska wrote:
> Introduce configurable generic interface for file
> system-wide event notifications to provide file
> systems with a common way of reporting any potential
> issues as they emerge.
> The notifications are to be issued through generic
> netlink interface, by a dedicated, for file system
> events, multicast group. The file systems might as
> well use this group to send their own custom messages.
> The events have been split into four base categories:
> information, warnings, errors and threshold notifications,
> with some very basic event types like running out of space
> or file system being remounted as read-only.
> Threshold notifications have been included to allow
> triggering an event whenever the amount of free space
> drops below a certain level - or levels to be more precise
> as two of them are being supported: the lower and the upper
> range. The notifications work both ways: once the threshold
> level has been reached, an event shall be generated whenever
> the number of available blocks goes up again re-activating
> the threshold.
> The interface has been exposed through a vfs. Once mounted,
> it serves as an entry point for the set-up where one can
> register for particular file system events.

Having a framework for notification for file systems is a great idea.
Your solution covers an important part of the possible application scope.

Before moving forward I suggest we should analyze if this scope should
be enlarged.

Many filesystems are remote (e.g. CIFS/Samba) or distributed over many
network nodes (e.g. Lustre). How should file system notification work here?

How will fuse file systems be served?

The current point of reference is a single mount point.
Every time I insert an USB stick several file system may be automounted.
I would like to receive events for these automounted file systems.

A similar case arises when starting new virtual machines. How will I
receive events on the host system for the file systems of the virtual

In your implementation events are received via Netlink.
Using Netlink for marking mounts for notification would create a much
more homogenous interface. So why should we use a virtual file system here?

Best regards

Heinrich Schuchardt

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