Messages in this thread | | | Date | Fri, 9 Jul 1999 10:56:34 +0200 | From | Pavel Machek <> | Subject | Re: Loop Devices over NFS don't work? |
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Hi!
> > > You could fall back to read/write in theory. There is an interesting project > > > for you 8) > > > > Really? Think about deadlocks. Both nbd and loop are _evil_. Mount > > sparse file over loopback, then write to both filessytems in heavy way > > to see why. THIS IS NOT EASY. > > Time to embarrass myself once more on l-k ;) Intuition tells me that deadlocks > and races need to be thought about, but unfortunately I can't see what they > are. > > How is writing to a filesystem on the loopbacked device simultaneously with > the hosting filesystem any different from writing to two files on the hosted > filesystem simultaneously?
Because for writing _datablock_ on loopfs you need to write _indirectblock_ on hosting filesystem. Something that could not have happened before. And now imagine writing _indirectblock_ on loop, which results into write of _indirectblock_ on hosting fs. I am not telling you I understand those issues. I just see it is not easy.
> Swapping, of course, is a different issue. Do we have any flags at the moment > which prevent people from trying to swap to inappropriate block devices (nbd, > certain raid levels with md, etc.)?
No and I'd like to see such patch.
Pavel
-- I'm really pavel@ucw.cz. Look at http://195.113.31.123/~pavel. Pavel Hi! I'm a .signature virus! Copy me into your ~/.signature, please!
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