Messages in this thread | | | Subject | Re: [RFC] per thread page reservation patch | From | Nikita Danilov <> | Date | Sat, 08 Jan 2005 02:17:31 +0300 |
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Andrew Morton <akpm@osdl.org> writes:
> Nikita Danilov <nikita@clusterfs.com> 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?
Yes, balancing may read tree or bitmap nodes from the disk.
> > Why does the filesystem risk going oom during the rebalance anyway? Is it > doing atomic allocations?
No, just __alloc_pages(GFP_KERNEL, 0, ...) returns NULL. When this happens, the only thing balancing can do is to panic.
Nikita.
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