Messages in this thread |  | | | Date | Mon, 5 Apr 2004 10:19:26 +0200 | | From | Jörn Engel <> | | Subject | Re: [PATCH] cowlinks v2 |
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On Sat, 3 April 2004 14:15:39 +0100, Jamie Lokier wrote: > Pavel Machek wrote: > > > > Could you not change it back to a normal inode when refcount becomes 1? > > > > > > You can only do that if the cowid object has a pointer to the last > > > remaining reference to it. That's possible, but more complicated and > > > would incur a little more I/O per cow operation. > > > > You'd have to have pointers to all references to it... because you > > can't tell in advance which one will be the last to go away. > > Exactly. Each of the cow pointers would need to be linked in a doubly > linked list containing them all.
I don't like the list idea. Having the extra cowid (I prefer inode) indirection costs a few bytes and one lookup, not much. The list is way too much overhead to get rid of so little in a few cases.
If you really want to, create a new syscall foldfile() that will remove the indirection for one file, if possible. Then userspace can do the ugly work of scanning for single-linked cowids (or just leave it).
Jörn
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