Re: [RFC] per thread page reservation patch

[Andrew Morton]

Nikita Danilov <nikita@xxxxxxxxxxxxx> wrote:
>
> > And the whole idea is pretty flaky really - how can one precalculate how
> > much memory an arbitrary md-on-dm-on-loop-on-md-on-NBD stack will want to
> > use?  It really would be better if we could drop the whole patch and make
> > reiser4 behave more sanely when its writepage is called with for_reclaim=1.
> 
> Reiser4 doesn't use this for ->writepage(), by the way. This is used by
> tree balancing code to assure that balancing cannot get -ENOMEM in the
> middle of tree modification, because undo is _so_ very complicated.

Oh.  And that involves performing I/O, yes?

Why does the filesystem risk going oom during the rebalance anyway?  Is it
doing atomic allocations?
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