Messages in this thread Patch in this message | | | Date | Fri, 11 Aug 2006 16:02:35 -0700 | From | "Nate Diller" <> | Subject | Re: partial reiser4 review comments |
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On 8/11/06, Hans Reiser <reiser@namesys.com> wrote: > Nate Diller wrote: > > > On 8/9/06, Hans Reiser <reiser@namesys.com> wrote: > > > >> Christoph Hellwig wrote: > >> > >> > I must admit that standalone code snipplet doesn't really tell me a > >> lot. > >> > > >> >Do you mean the possibility to pass around a filesystem-defined > >> structure > >> >to multiple allocator calls? I'm pretty sure can add that, I though it > >> >would be useful multiple times in the past but always found ways around > >> >it. > >> > > >> > > >> > > >> Assuming I understand your discussion, I see two ways to go, one is to > >> pass around fs specific state and continue to call into the FS many > >> times, and the other is to instead provide the fs with helper functions > >> that accomplish readahead calculation, page allocation, etc., and let > >> the FS keep its state naturally without having to preserve it in some fs > >> defined structure. The second approach would be cleaner code design, > >> that would also ease cross-os porting of filesystems, in my view. > > > > > > the second approach is the one i was heading towards with my > > unfinished a_ops patches. *please* won't someone pay me to do that > > work... > > > > NATE > > > > > You might describe it in a paragraph or so instead of just mentioning > it.....;-) >
start by making tree_lock (write) private, using the interface detailed below. No one should be able to add/remove pages from the address space without going through the a_ops interface. this patch is part of a (much) larger unfinished, and outdated, set intended to put this interface in place. people familiar with this code will immediately note that there are a few hard problems to solve here, most notably the various {truncate|invalidate}_mapping_pages calls, and the locking involved. Cleaning up the inode reclaim paths a bit should help this, and that work is unfinished as well.
I'm always hesitant to post stuff like this, because -ENOPATCH is really an appropriate response here.
NATE
diff -urpN linux-2.6.15-rc5-mm1/include/linux/fs.h linux-extent/include/linux/fs.h --- linux-2.6.15-rc5-mm1/include/linux/fs.h 2005-12-10 16:49:30.000000000 -0800 +++ linux-extent/include/linux/fs.h 2006-08-11 15:47:19.000000000 -0700 @@ -340,18 +340,33 @@ struct address_space; struct writeback_control;
struct address_space_operations { - int (*writepage)(struct page *page, struct writeback_control *wbc); - int (*readpage)(struct file *, struct page *); - int (*sync_page)(struct page *); - - /* Write back some dirty pages from this mapping. */ - int (*writepages)(struct address_space *, struct writeback_control *); - /* Set a page dirty */ + /* takes lock to move lists, update counts */ int (*set_page_dirty)(struct page *page); + /* get rid of this, all it does is unplug blkdev */ + int (*sync_page)(struct page *);
+ /* + * Write back dirty pages / invalidate all pages that fall within + * the given page range (end byte inclusive). These only affect + * pages already cached in this mapping. + */ + int (*writepages)(struct address_space *mapping, + struct writeback_control *wbc); + int (*invalidate_range)(struct address_space *mapping, + pgoff_t index, unsigned nr_pages); + + /* + * Read / create pages within the given index extent. These + * silently skip any pages which are already cached in this mapping. + * + * Return the number of pages allocated within the range, or an error. + */ + /* filp here is wierd */ int (*readpages)(struct file *filp, struct address_space *mapping, - struct list_head *pages, unsigned nr_pages); + pgoff_t index, unsigned nr_pages); + int (*instantiate_range)(struct address_space *mapping, pgoff_t index, + unsigned nr_pages);
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