Messages in this thread | | | Date | Tue, 1 Aug 2006 12:14:58 -0700 | From | "Nate Diller" <> | Subject | Re: reiser4: maybe just fix bugs? |
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On 8/1/06, Andrew Morton <akpm@osdl.org> wrote: > On Tue, 01 Aug 2006 15:24:37 +0400 > "Vladimir V. Saveliev" <vs@namesys.com> wrote: > > > > >The writeout code is ugly, although that's largely due to a mismatch between > > > >what reiser4 wants to do and what the VFS/MM expects it to do. > > > > Yes. reiser4 writeouts atoms. Most of pages get into atoms via > > sys_write. But pages dirtied via shared mapping do not. They get into > > atoms in reiser4's writepages address space operation. > > It think you mean ->writepage - reiser4 desn't implement ->writepages(). > > I assume you considered hooking into ->set_page_dirty() to do the > add-to-atom thing earlier on? > > We'll merge mm-tracking-shared-dirty-pages.patch into 2.6.19-rc1, which > would make that approach considerably more successful, I expect. > ->set_page_dirty() is a bit awkward because it can be called under > spinlock. > > Maybe comething could also be gained from the new > vm_operations_struct.page_mkwrite(), although that's less obvious... > > > That is why > > reiser4_sync_inodes has two steps: on first one it calls > > generic_sync_sb_inodes to call writepages for dirty inodes to capture > > pages dirtied via shared mapping into atoms. Second step flushes atoms. > > > > > > > > > I agree --- both with it being ugly, and that being part of why. > > > > > > > If it > > > >works, we can live with it, although perhaps the VFS could be made smarter. > > > > > > > > > > > I would be curious regarding any ideas on that. Next time I read > > > through that code, I will keep in mind that you are open to making VFS > > > changes if it improves things, and I will try to get clever somehow and > > > send it by you. Our squalloc code though is I must say the most > > > complicated and ugliest piece of code I ever worked on for which every > > > cumulative ugliness had a substantive performance advantage requiring us > > > to keep it. If you spare yourself from reading that, it is > > > understandable to do so. > > > > > > >I'd say that resier4's major problem is the lack of xattrs, acls and > > > >direct-io. That's likely to significantly limit its vendor uptake. > > > > xattrs is really a problem. > > That's not good. The ability to properly support SELinux is likely to be > important.
i disagreee that it will be difficult. unfortunately, the patch that I am working on right now, which fixes the various reiser4 specific functions to avoid using VFS data structures unless needed, is a prerequisite to enabling xattrs. creating it is a time of tedium for me, and it will cause a bit of internal churn (1000 lines and counting). it's all in the fs/reiser4 directory though, and it should cause minimal disruption, as far as runtime bugs introduced.
once that's taken care of, i will be delighted to enable xattr support in a way that will make selinux and beagle and such run as expected, and will have the added advantage of some major scalability improvements for certain lookup and update operations.
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