Messages in this thread | | | Date | Mon, 9 Jul 2007 17:59:47 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: [RFC] fsblock |
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On Tue, 10 Jul 2007, Nick Piggin wrote:
> > Hmmm.... I did not notice that yet but then I have not done much work > > there. > > Notice what?
The bad code for the buffer heads.
> > > - A real "nobh" mode. nobh was created I think mainly to avoid problems > > > with buffer_head memory consumption, especially on lowmem machines. It > > > is basically a hack (sorry), which requires special code in filesystems, > > > and duplication of quite a bit of tricky buffer layer code (and bugs). > > > It also doesn't work so well for buffers with non-trivial private data > > > (like most journalling ones). fsblock implements this with basically a > > > few lines of code, and it shold work in situations like ext3. > > > > Hmmm.... That means simply page struct are not working... > > I don't understand you. jbd needs to attach private data to each bh, and > that can stay around for longer than the life of the page in the pagecache.
Right. So just using page struct alone wont work for the filesystems.
> There are no changes to the filesystem API for large pages (although I > am adding a couple of helpers to do page based bitmap ops). And I don't > want to rely on contiguous memory. Why do you think handling of large > pages (presumably you mean larger than page sized blocks) is strange?
We already have a way to handle large pages: Compound pages.
> Conglomerating the constituent pages via the pagecache radix-tree seems > logical to me.
Meaning overhead to handle each page still exists? This scheme cannot handle large contiguous blocks as a single entity?
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