Messages in this thread | | | Date | Mon, 18 Dec 2000 11:44:04 +0000 | From | "Stephen C. Tweedie" <> | Subject | Re: Test12 ll_rw_block error. |
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Hi,
On Sat, Dec 16, 2000 at 07:08:02PM -0600, Russell Cattelan wrote: > > There is a very clean way of doing this with address spaces. It's > > something I would like to see done properly for 2.5: eliminate all > > knowledge of buffer_heads from the VM layer. It would be pretty > > simple to remove page->buffers completely and replace it with a > > page->private pointer, owned by whatever address_space controlled the > > page. Instead of trying to unmap and flush buffers on the page > > directly, these operations would become address_space operations. > > Yes this is a lot of what page buf would like to do eventually. > Have the VM system pressure page_buf for pages which would > then be able to intelligently call the file system to free up cached pages. > A big part of getting Delay Alloc to not completely consume all the > system pages, is being told when it's time to start really allocating disk > space and push pages out.
Delayed allocation is actually much easier, since it's entirely an operation on logical page addresses, not physical ones --- by definition you don't have any buffer_heads yet because you haven't decided on the disk blocks. If you're just dealing with pages, not blocks, then the address_space is the natural way of dealing with it already.
Only the full semantics of the flush callback have been missing to date, and with 2.4.0-test12 even that is mostly solved, since page_launder will give you the writeback() callbacks you need to flush things to disk when you start getting memory pressure. You can even treat the writepage() as an advisory call.
--Stephen - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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