Re: Elastic Quota File System (EQFS)

[Pavel Machek <pavel@ucw.cz>]

Hi!

> Case closed, anyway. It belongs in the kernel only if there is no
> reasonable way to do it in userspace.

But... there's no reasonable way to do this in userspace.

Two pieces of kernel support are needed:

1) some way to indicate "this file is elastic" (okay perhaps xattrs
can do this already)

and either

2a) file selection/deletion in kernel

or

2b) assume that disk does not fill up faster than 1GB/sec, allways
keep 1GB free, make "deleting" daemon poll each second [ugly,
unreliable]

or

2c) just before returning -ENOSPC, synchronously tell userspace to
free space, and retry the operation.

BTW 2c) would be also usefull for undelete. Unfortunately 2c looks
very complex, too; it might be easier to do 2a than 2c.
								Pavel

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