[Tux3] Cool features

OGAWA Hirofumi hirofumi at mail.parknet.co.jp
Wed Jan 7 07:21:55 PST 2009


Daniel Phillips <phillips at phunq.net> writes:

>> Filesystem freeze :
>> Get an utility that flush cache and return something when it's done, then
>> freeze IO on disk and throttle/stack in a memory buffer until it's full.
>> When it's full, return again something and resume normal operation, or
>> freeze IO until we ask to resume. This in order to take clean snapshots when
>> backend support versionning. Even if it's not necessary due to tux3 design,
>> it would be nice to be able to do it in order to ensure that some IO are
>> commited to disk, then get some time to do something to the disk backend,
>> with no impact on the filesystem side.
>
> I think all you want there is the ability to treat a snapshot as a
> barrier: user asks for a snapshot, Tux3 starts a new delta and sets a
> flag on it; when that snapshot has committed, the snapshot request
> is acknowledged.  That way, the user gets a snapshot of what has been
> sent to the filesystem most recently, without needing to stall the
> filesystem throughput.
>
> Tux3 does not need a new memory buffer for this, the needed mechanism
> is just what has already been designed.

FWIW, if it is needed, we just implement ->write_super_lockfs nad unlockfs.
And I guess it shouldn't be hard.

Thanks.
-- 
OGAWA Hirofumi <hirofumi at mail.parknet.co.jp>

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