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Re: Replace lockmgr for vnodes

On Sat, Jan 26, 2008 at 07:39:12PM +0000, David Holland wrote:
> On Sat, Jan 26, 2008 at 05:57:50PM +0000, Andrew Doran wrote:
>  >> 4) I think we can rip out the "UPPER LOCK" stuff in layerfs. It dated 
> from 
>  >> when lower file systems didn't do locking. The only thing now that 
> doesn't 
>  >> export a vn_lock is unionfs, which does do correct locking. Sorry, I've 
>  >> been meaning to kill it but haven't gotten to it.
>  > 
>  > Sounds like union-over-union should be prevented? I'll see about removing
>  > it.

Actually, a union-over-union should be fine in this respect. It could just 
call down for locking when it needed to.

> It seems like if unionfs does proper locking, it ought to be able to
> take unions of anything, including other unionfses.

We should bar unions-of-unions for another reason, however. The hooks we 
use for merging readdir don't recurse right. So while the vnodes would 
work (I think), you couldn't correctly read a directory.

Take care,


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