Messages in this thread |  | | Subject | Re: NFS locking bug -- limited mtime resolution means nfs_lock() does not provide coherency guarantee | Date | Thu, 14 Sep 2000 17:12:35 +0200 (MEST) | From | (Rogier Wolff) |
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Theodore Y. Ts'o wrote: > Date: Thu, 14 Sep 2000 15:09:35 +0200 (CEST) > From: Trond Myklebust <trond.myklebust@fys.uio.no> > > Would it perhaps make sense to use one of these last 'free' fields > as a pointer to an 'inode entension'? > If you still want ext2fs to be able to accommodate new projects and > ideas, then it seems that being able to extend the inode is a > desirable feature, but perhaps this overlaps with the apparent plans > for adding resource forks? > > For stuff that's not commonly used, perhaps. The problem is that you > take a speed hit when you have to seek somewhere else to get at the > inode extension. So for something which is going to have to be > referenced for every stat() or getattr() operation, there are a real > performance issues with doing something like that.
The "right" way to do this is to have a "this spot is in use, but you don't understand it" indication for an inode (*). The "expansion ptr" can then normally point to the directly following inode, but also somewhere completely different.
So a "new" system would allocate a new inode in the directly following spot. But when a "new" system would need the extension part on an old filesystem, it would allocate the nearest inode and point the extension ptr there.
Roger.
(*) Actually the kernel only needs the "it's in use" part. fsck needs to know what it means or to properly ignore it....
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